Guest guest Posted December 18, 2004 Report Share Posted December 18, 2004 Hello everyone. Certain temperature and humidity ranges are written as very condusive to mold, but from a recent experience it seems like mold needs a physically saturated food source to get started. My experience is from the effects of a hurricane. My home, a two story town house, was flooded by storm surge however only 4 inches made it inside and the ground floor has all concrete walls. It was a couple days after the storm before we could get back into our home and we had to bleach the baseboard trim to kill visible mold, and rather than take chances we bleached all the trim. I was without power for a month, and it typically averaged inside close to 86F at 85% RH for three weeks, then when I managed to get a small window AC unit running from my generator, it was a week of 83F @ 68% RH. I did not get an explosion of mold in the upper levels with all that sheet rock. My office is in an industrial 'butler' building and the high sea water mark was 46 " . My ceiling is under a mezzanine and some roof panels were lost in the storm and rain water was getting on the mezzanine. My walls quickly 'molded' up to the high water mark, and a couple days later the ceiling was showing mold as well. Both the walls and the ceilings were wet. I was forced to gut this office. I will never buy particle board book cases again either as they all collapsed. In both of these situations, with no power, there was no AC operating and therefore there was nothing cooler than the ambient dewpoint which howvers around 80F from June to the end of Novemeber. I was reading ASHRAE's Humidity COntrol Design Guide, Chapter 7, http://www.masongrant.com/pdf/design_guide/ASHRAE_HCDG_C7_Mold.pdf and it comments how spore cases seem to have enzymes on them. Moisture in the food source dissolves these enzymes, and through osmosis the spores receive food that the enzymes have broken down to liquid form. It just seems to me that the high indoor RH levels are condusive to mold, but they don't really seem to cause food source to be wet enough to 'germinate' spores. I can see humid air getting trapped in drawers, closets, behind furniture and then when the air conditioning runs, it creates localized condensation in these out of the way places and starts the mold. I realize there are spores everywhere, but it does not seem like the spores 'spontaneously germinate' from high relative humidities. From what happend to me it looks like it needs a wet spot to get established. I am good at designing to maintain conditions that prevent the humidity levels condusive to mold, I am just looking for some comments on all the experts in here on what makes the mold grow. Does mold need a wet saturated food source to start growing? Quote Link to comment Share on other sites More sharing options...
Guest guest Posted December 19, 2004 Report Share Posted December 19, 2004 Chronic high humidity can allow mold to develop but it does take much longer for that development to occur than it would if a liquid moisture source were to be present. The presence of moisture in liquid form makes all of the vulnerable wall surfaces much more "sticky" to mold spores of all types. Suitably wetted walls will therefore tend to collect and hold more of the available aerosolized mold spores which may then form growing colonies if they should happen to have an appetite for the particular substrate involved. Also, a wetted wall will have a wide range of moisture levels as the drywall absorbs and wicks up moisture in liquid form. In a rising water flood situation for example, the moisture content at the bottom of the wall will be higher than that above the flood line. This soaking up (via capillary action) creates a gradient of moisture contents as you go up the wall surface. Since mold species have differing water activity levels (Aw), there is likely to be a "sweet spot" on the wetted wall somewhere for just about any particular mold species that happens to have spores present at the time. This would logically increases the odds that some kind of mold development is going to occur somewhere on that wetted wall. With just high humidity on the other hand, it can take a very long time for the wall material to absorb enough moisture vapor out of the air to obtain a particular surface moisture content that might be conducive to mold development. Also, the circumstances have to be right to allow the wall material to actually absorb the available moisture. A higher temperature on the wall surface than the ambient air for example may actually be causing some drying to occur and the vapor permeability of the paint may even come into play. There are also circumstances that might prevent mold spores from readily sticking to the wall surfaces even if the moisture level of the drywall actually does reach a conducive level. Having said all of that, I will say that I have seen mold develop on drywall as a result of chronic high humidity. Let me describe two such cases. Case one was mold that developed on a hallway ceiling and on the upper walls of the hallway above the door openings. This was a small hallway between bedrooms with a pulldown attic stairway installed. The problem was poor attic ventilation. The attic was incredibly hot and humid and that air leaked down into the living space through the poor sealing stairway. There was no impetus for air movement in the upper ceiling area and that hot humid air just hung out up high at the top area of the hallway. The mold began to appear one summer when the house was about a year old. Case two was in the home of a guy who was in the ceiling fan business. He was a big believer in ceiling fans and literally has a ceiling fan in every room of his house. One day he just decided to just turn off his A/C system and rely solely on ceiling fans for comfort. This is Houston so you can imagin how hot and sticky his house was (but he always had a good breeze going). Some time during the second summer of this he began to notice mold growing in areas where the air was generally stagnant (within closets and behind furniture placed close to the walls). As you can see, in both of the cases above it took at least a year (or more) of chronic high humidity for visible mold to develop. It does seems then that under very high humidity situations mold will eventually develop. There are however many more variables involved than exist in a wetted-by-liquid scenario and the time frame for onset (at least in my personal experience) would seem to be measured in months rather than days. Just a few weeks is probalby not enough time for a problem to develop under just a high humidity situation. Phil S. Getting Mold Started Hello everyone.Certain temperature and humidity ranges are written as very condusive to mold, but from a recent experience it seems like mold needs a physically saturated food source to get started. My experience is from the effects of a hurricane. My home, a two story town house, was flooded by storm surge however only 4 inches made it inside and the ground floor has all concrete walls.It was a couple days after the storm before we could get back into our home and we had to bleach the baseboard trim to kill visible mold, and rather than take chances we bleached all the trim.I was without power for a month, and it typically averaged inside close to 86F at 85% RH for three weeks, then when I managed to get a small window AC unit running from my generator, it was a week of 83F @ 68% RH.I did not get an explosion of mold in the upper levels with all that sheet rock. My office is in an industrial 'butler' building and the high sea water mark was 46". My ceiling is under a mezzanine and some roof panels were lost in the storm and rain water was getting on the mezzanine.My walls quickly 'molded' up to the high water mark, and a couple days later the ceiling was showing mold as well. Both the walls and the ceilings were wet. I was forced to gut this office. I will never buy particle board book cases again either as they all collapsed.In both of these situations, with no power, there was no AC operating and therefore there was nothing cooler than the ambient dewpoint which howvers around 80F from June to the end of Novemeber.I was reading ASHRAE's Humidity COntrol Design Guide, Chapter 7, http://www.masongrant.com/pdf/design_guide/ASHRAE_HCDG_C7_Mold.pdfand it comments how spore cases seem to have enzymes on them. Moisture in the food source dissolves these enzymes, and through osmosis the spores receive food that the enzymes have broken down to liquid form.It just seems to me that the high indoor RH levels are condusive to mold, but they don't really seem to cause food source to be wet enough to 'germinate' spores. I can see humid air getting trapped in drawers, closets, behind furniture and then when the air conditioning runs, it creates localized condensation in these out of the way places and starts the mold.I realize there are spores everywhere, but it does not seem like the spores 'spontaneously germinate' from high relative humidities. From what happend to me it looks like it needs a wet spot to get established.I am good at designing to maintain conditions that prevent the humidity levels condusive to mold, I am just looking for some comments on all the experts in here on what makes the mold grow. Does mold need a wet saturated food source to start growing?FAIR USE NOTICE:This site contains copyrighted material the use of which has not always been specifically authorized by the copyright owner. We are making such material available in our efforts to advance understanding of environmental, political, human rights, economic, democracy, scientific, and social justice issues, etc. We believe this constitutes a 'fair use' of any such copyrighted material as provided for in section 107 of the US Copyright Law. In accordance with Title 17 U.S.C. Section 107, the material on this site is distributed without profit to those who have expressed a prior interest in receiving the included information for research and educational purposes. For more information go to: http://www.law.cornell.edu/uscode/17/107.shtml. If you wish to use copyrighted material from this site for purposes of your own that go beyond 'fair use', you must obtain permission from the copyright owner. Quote Link to comment Share on other sites More sharing options...
Guest guest Posted December 20, 2004 Report Share Posted December 20, 2004 Phil, It appears in your first paragraph you dispute that high humidity can provide the same surface conditions as your liquid moisture content hypothesis. The moisture content of a surface is often defined by the RH in air. A high RH over a period of time (e.g., 80%) will cause the surface of a material to be 0.80, sufficient enough to support at the surface many of the water related spores we are concerned about that involve wet buildings. In subsequent paragraphs you appear to take a different point of view. It can't be both ways. Now that you are talking about RH, add more discussion about temperature and air movement, and factors that contribute to building wetness followed by methods involving structural drying of wet buildings before mold grows. Moffett -----Original Message-----From: talk2ps@... Sent: Sunday, December 19, 2004 11:05 PMTo: iequality Subject: Re: Getting Mold Started Chronic high humidity can allow mold to develop but it does take much longer for that development to occur than it would if a liquid moisture source were to be present. The presence of moisture in liquid form makes all of the vulnerable wall surfaces much more "sticky" to mold spores of all types. Suitably wetted walls will therefore tend to collect and hold more of the available aerosolized mold spores which may then form growing colonies if they should happen to have an appetite for the particular substrate involved. Also, a wetted wall will have a wide range of moisture levels as the drywall absorbs and wicks up moisture in liquid form. In a rising water flood situation for example, the moisture content at the bottom of the wall will be higher than that above the flood line. This soaking up (via capillary action) creates a gradient of moisture contents as you go up the wall surface. Since mold species have differing water activity levels (Aw), there is likely to be a "sweet spot" on the wetted wall somewhere for just about any particular mold species that happens to have spores present at the time. This would logically increases the odds that some kind of mold development is going to occur somewhere on that wetted wall. With just high humidity on the other hand, it can take a very long time for the wall material to absorb enough moisture vapor out of the air to obtain a particular surface moisture content that might be conducive to mold development. Also, the circumstances have to be right to allow the wall material to actually absorb the available moisture. A higher temperature on the wall surface than the ambient air for example may actually be causing some drying to occur and the vapor permeability of the paint may even come into play. There are also circumstances that might prevent mold spores from readily sticking to the wall surfaces even if the moisture level of the drywall actually does reach a conducive level. Having said all of that, I will say that I have seen mold develop on drywall as a result of chronic high humidity. Let me describe two such cases. Case one was mold that developed on a hallway ceiling and on the upper walls of the hallway above the door openings. This was a small hallway between bedrooms with a pulldown attic stairway installed. The problem was poor attic ventilation. The attic was incredibly hot and humid and that air leaked down into the living space through the poor sealing stairway. There was no impetus for air movement in the upper ceiling area and that hot humid air just hung out up high at the top area of the hallway. The mold began to appear one summer when the house was about a year old. Case two was in the home of a guy who was in the ceiling fan business. He was a big believer in ceiling fans and literally has a ceiling fan in every room of his house. One day he just decided to just turn off his A/C system and rely solely on ceiling fans for comfort. This is Houston so you can imagin how hot and sticky his house was (but he always had a good breeze going). Some time during the second summer of this he began to notice mold growing in areas where the air was generally stagnant (within closets and behind furniture placed close to the walls). As you can see, in both of the cases above it took at least a year (or more) of chronic high humidity for visible mold to develop. It does seems then that under very high humidity situations mold will eventually develop. There are however many more variables involved than exist in a wetted-by-liquid scenario and the time frame for onset (at least in my personal experience) would seem to be measured in months rather than days. Just a few weeks is probalby not enough time for a problem to develop under just a high humidity situation. Phil S. Getting Mold Started Hello everyone.Certain temperature and humidity ranges are written as very condusive to mold, but from a recent experience it seems like mold needs a physically saturated food source to get started. My experience is from the effects of a hurricane. My home, a two story town house, was flooded by storm surge however only 4 inches made it inside and the ground floor has all concrete walls.It was a couple days after the storm before we could get back into our home and we had to bleach the baseboard trim to kill visible mold, and rather than take chances we bleached all the trim.I was without power for a month, and it typically averaged inside close to 86F at 85% RH for three weeks, then when I managed to get a small window AC unit running from my generator, it was a week of 83F @ 68% RH.I did not get an explosion of mold in the upper levels with all that sheet rock. My office is in an industrial 'butler' building and the high sea water mark was 46". My ceiling is under a mezzanine and some roof panels were lost in the storm and rain water was getting on the mezzanine.My walls quickly 'molded' up to the high water mark, and a couple days later the ceiling was showing mold as well. Both the walls and the ceilings were wet. I was forced to gut this office. I will never buy particle board book cases again either as they all collapsed.In both of these situations, with no power, there was no AC operating and therefore there was nothing cooler than the ambient dewpoint which howvers around 80F from June to the end of Novemeber.I was reading ASHRAE's Humidity COntrol Design Guide, Chapter 7, http://www.masongrant.com/pdf/design_guide/ASHRAE_HCDG_C7_Mold.pdfand it comments how spore cases seem to have enzymes on them. Moisture in the food source dissolves these enzymes, and through osmosis the spores receive food that the enzymes have broken down to liquid form.It just seems to me that the high indoor RH levels are condusive to mold, but they don't really seem to cause food source to be wet enough to 'germinate' spores. I can see humid air getting trapped in drawers, closets, behind furniture and then when the air conditioning runs, it creates localized condensation in these out of the way places and starts the mold.I realize there are spores everywhere, but it does not seem like the spores 'spontaneously germinate' from high relative humidities. From what happend to me it looks like it needs a wet spot to get established.I am good at designing to maintain conditions that prevent the humidity levels condusive to mold, I am just looking for some comments on all the experts in here on what makes the mold grow. Does mold need a wet saturated food source to start growing?FAIR USE NOTICE:This site contains copyrighted material the use of which has not always been specifically authorized by the copyright owner. We are making such material available in our efforts to advance understanding of environmental, political, human rights, economic, democracy, scientific, and social justice issues, etc. We believe this constitutes a 'fair use' of any such copyrighted material as provided for in section 107 of the US Copyright Law. In accordance with Title 17 U.S.C. Section 107, the material on this site is distributed without profit to those who have expressed a prior interest in receiving the included information for research and educational purposes. For more information go to: http://www.law.cornell.edu/uscode/17/107.shtml. If you wish to use copyrighted material from this site for purposes of your own that go beyond 'fair use', you must obtain permission from the copyright owner. FAIR USE NOTICE:This site contains copyrighted material the use of which has not always been specifically authorized by the copyright owner. We are making such material available in our efforts to advance understanding of environmental, political, human rights, economic, democracy, scientific, and social justice issues, etc. We believe this constitutes a 'fair use' of any such copyrighted material as provided for in section 107 of the US Copyright Law. In accordance with Title 17 U.S.C. Section 107, the material on this site is distributed without profit to those who have expressed a prior interest in receiving the included information for research and educational purposes. For more information go to: http://www.law.cornell.edu/uscode/17/107.shtml. If you wish to use copyrighted material from this site for purposes of your own that go beyond 'fair use', you must obtain permission from the copyright owner. Quote Link to comment Share on other sites More sharing options...
Guest guest Posted December 22, 2004 Report Share Posted December 22, 2004 , I certainly did not intend to appear as wanting to have it both ways in my previous post. The point I guess I failed to make is that it takes much longer for water vapor in the form of high humidity to create conditions conducive to mold development on a given surface than it takes when water in liquid form is present on that same surface. Other involved variabilities also make the moisture vapor mold scenario much less of a sure thing. Even still (in my personal experience) water vapor in the air is capable of encouraging mold development on the surface of a suitable food source under the right conditions and given enough time. My point from the previous post was (and remains) that conditions will "ripen" MUCH quicker when water in liquid form is present than it will when water vapor alone is present. I think it is this inherent delay in onset that leads many people to conclude that water in vapor form only is not capable of allowing mold to develop. This opinion is often allowed to galvanize precisely because of the significant time delay in onset. In many cases mold growth is not able to development before conditions change and lower humidity levels allow for drying to take place. This occurs when the high humidity event does not go on long enough to allow the material to absorb enough moisture to allow for mold development. You are correct in pointing out that the RH as a percentage will eventually equated to a particular AW on the given substrate as a ratio. A potential food source surface will eventually reach an equilibrium of sorts with the RH it has been subjected to over a long enough period of time (be that weeks, months, or even years). For the sake of example, let us presume that we have drywall material that is being chronically subjected to a RH of 85%. At some point in time we might expect that the drywall will have absorb enough moisture (in vapor form) so that its outer surface will reach equilibrium with the RH and that that surface will be capable of supporting the development and growth of fungi that have a minimum and maximum AW range that encompasses .85 The above is, admittedly, a very simplistic view for the sake of example and the issues are much more complex when dealing with just water vapor in the form of high humidity. You touched on some of these complexities when you posed your interrogatory response to my previous posting… Quote…"Now that you are talking about RH, add more discussion about temperature and air movement, and factors that contribute to building wetness followed by methods involving structural drying of wet buildings before mold grows." As you alluded in the above quote, there are many factors involved in how quickly and thoroughly a given surface will achieve its equilibrium with the RH. Some surfaces resist absorption of moisture vapor better than others depending on their particular permeability and their facility to retain the moisture. Imagin, if you will, a desiccant product that is capable of literally sucking the moisture out of the air and compare that to an ordinary piece of drywall material and you will get the concept that I am trying to explain. These are mechanical variables within the absorbing materials and surfaces themselves. Other internal and external variables also exist and factors such as the temperature of the material and airflow currents across the surfaces will also affect the material’s ability to absorb and retain the available moisture vapor (as you pointed out). It should be understood that all of the variabilities involved might just end up precluding a particular surface material from ever absorbing enough moisture vapor to actually reach true equilibrium with the RH. Under the right conditions however, it can happen that enough moisture will be absorbed to allow the development of mold growth but conditions have to be "just right" for a very long enough period of time. Most of us naturally tend to focus much more on the moisture-in-liquid-form kind of problems and rightfully so. The presence of water in liquid form tends to either ‘wash away’ or mitigate many of the variables discussed above. Lets face it, when you throw liquid water into the mix and the all of the complex variabilities quickly begin to look like inevitabilities. Phil S. Getting Mold Started Hello everyone.Certain temperature and humidity ranges are written as very condusive to mold, but from a recent experience it seems like mold needs a physically saturated food source to get started. My experience is from the effects of a hurricane. My home, a two story town house, was flooded by storm surge however only 4 inches made it inside and the ground floor has all concrete walls.It was a couple days after the storm before we could get back into our home and we had to bleach the baseboard trim to kill visible mold, and rather than take chances we bleached all the trim.I was without power for a month, and it typically averaged inside close to 86F at 85% RH for three weeks, then when I managed to get a small window AC unit running from my generator, it was a week of 83F @ 68% RH.I did not get an explosion of mold in the upper levels with all that sheet rock. My office is in an industrial 'butler' building and the high sea water mark was 46". My ceiling is under a mezzanine and some roof panels were lost in the storm and rain water was getting on the mezzanine.My walls quickly 'molded' up to the high water mark, and a couple days later the ceiling was showing mold as well. Both the walls and the ceilings were wet. I was forced to gut this office. I will never buy particle board book cases again either as they all collapsed.In both of these situations, with no power, there was no AC operating and therefore there was nothing cooler than the ambient dewpoint which howvers around 80F from June to the end of Novemeber.I was reading ASHRAE's Humidity COntrol Design Guide, Chapter 7, http://www.masongrant.com/pdf/design_guide/ASHRAE_HCDG_C7_Mold.pdfand it comments how spore cases seem to have enzymes on them. Moisture in the food source dissolves these enzymes, and through osmosis the spores receive food that the enzymes have broken down to liquid form.It just seems to me that the high indoor RH levels are condusive to mold, but they don't really seem to cause food source to be wet enough to 'germinate' spores. I can see humid air getting trapped in drawers, closets, behind furniture and then when the air conditioning runs, it creates localized condensation in these out of the way places and starts the mold.I realize there are spores everywhere, but it does not seem like the spores 'spontaneously germinate' from high relative humidities. From what happend to me it looks like it needs a wet spot to get established.I am good at designing to maintain conditions that prevent the humidity levels condusive to mold, I am just looking for some comments on all the experts in here on what makes the mold grow. Does mold need a wet saturated food source to start growing?FAIR USE NOTICE:This site contains copyrighted material the use of which has not always been specifically authorized by the copyright owner. We are making such material available in our efforts to advance understanding of environmental, political, human rights, economic, democracy, scientific, and social justice issues, etc. We believe this constitutes a 'fair use' of any such copyrighted material as provided for in section 107 of the US Copyright Law. In accordance with Title 17 U.S.C. Section 107, the material on this site is distributed without profit to those who have expressed a prior interest in receiving the included information for research and educational purposes. For more information go to: http://www.law.cornell.edu/uscode/17/107.shtml. If you wish to use copyrighted material from this site for purposes of your own that go beyond 'fair use', you must obtain permission from the copyright owner. FAIR USE NOTICE:This site contains copyrighted material the use of which has not always been specifically authorized by the copyright owner. We are making such material available in our efforts to advance understanding of environmental, political, human rights, economic, democracy, scientific, and social justice issues, etc. We believe this constitutes a 'fair use' of any such copyrighted material as provided for in section 107 of the US Copyright Law. In accordance with Title 17 U.S.C. Section 107, the material on this site is distributed without profit to those who have expressed a prior interest in receiving the included information for research and educational purposes. For more information go to: http://www.law.cornell.edu/uscode/17/107.shtml. If you wish to use copyrighted material from this site for purposes of your own that go beyond 'fair use', you must obtain permission from the copyright owner. FAIR USE NOTICE:This site contains copyrighted material the use of which has not always been specifically authorized by the copyright owner. We are making such material available in our efforts to advance understanding of environmental, political, human rights, economic, democracy, scientific, and social justice issues, etc. We believe this constitutes a 'fair use' of any such copyrighted material as provided for in section 107 of the US Copyright Law. In accordance with Title 17 U.S.C. Section 107, the material on this site is distributed without profit to those who have expressed a prior interest in receiving the included information for research and educational purposes. For more information go to: http://www.law.cornell.edu/uscode/17/107.shtml. If you wish to use copyrighted material from this site for purposes of your own that go beyond 'fair use', you must obtain permission from the copyright owner. Quote Link to comment Share on other sites More sharing options...
Guest guest Posted July 18, 2005 Report Share Posted July 18, 2005 I respectfully disagree. I've inspected many homes that have stood vacant and closed up for extended periods of time and observed many Aspergillus colonies on the ceilings and walls. Ed Gerhardt Surelock Homes, Inc Chapel Hill, NC Quote Link to comment Share on other sites More sharing options...
Guest guest Posted July 18, 2005 Report Share Posted July 18, 2005 I agree that spores will not germinate in humid air alone. However, I have seen high humidity cause mold on hygroscopic surfaces many times -- without condensation. Examples are leather clothing items stored in a box or closet and certain engineered wood products (microlam girders and TJI joists). Moisture is chemically "captured" and held in sufficient amounts in the porous organic materials to germinate spores. There are plenty of instances where you can have a "wet food source" caused only by humid air without reaching the dew point. Steve Temes High humidity itself does not seem to cause mold. Condensation as a result of high humidity can. I base my opinion on observations of non-air conditioned homes in a humid tropical environment, where the only cooling available is opening windows to let the trade winds blow through and to run ceiling fans. Air with an 80F dew point blowing through, no mold. Even in older 'historical' homes. Air condition that home and maintain a temperature below the ambient dew point and you can run the risk of humid air condensating on a surface cooler than the ambient dewpoint. Wet spot could and will most likely start mold. Other observations are in the old thread below. Basically observations that a wet food source is needed, rather than spores grabbing moisture directly from the air at certain temperature/humidity levels. > > >Hello everyone. > >Certain temperature and humidity ranges are written as very >condusive to mold, but from a recent experience it seems like mold >needs a physically saturated food source to get started. > >My experience is from the effects of a hurricane. My home, a two >story town house, was flooded by storm surge however only 4 inches >made it inside and the ground floor has all concrete walls. > >It was a couple days after the storm before we could get back into >our home and we had to bleach the baseboard trim to kill visible >mold, and rather than take chances we bleached all the trim. > >I was without power for a month, and it typically averaged inside >close to 86F at 85% RH for three weeks, then when I managed to get a >small window AC unit running from my generator, it was a week of 83F >@ 68% RH. > >I did not get an explosion of mold in the upper levels with all that >sheet rock. > >My office is in an industrial 'butler' building and the high sea >water mark was 46". My ceiling is under a mezzanine and some roof >panels were lost in the storm and rain water was getting on the >mezzanine. > >My walls quickly 'molded' up to the high water mark, and a couple >days later the ceiling was showing mold as well. Both the walls and >the ceilings were wet. I was forced to gut this office. I will never >buy particle board book cases again either as they all collapsed. > >In both of these situations, with no power, there was no AC >operating and therefore there was nothing cooler than the ambient >dewpoint which howvers around 80F from June to the end of Novemeber. > >I was reading ASHRAE's Humidity COntrol Design Guide, Chapter 7, >http://www.masongrant.com/pdf/design_guide/ASHRAE_HCDG_C7_Mold.pdf >and it comments how spore cases seem to have enzymes on them. >Moisture in the food source dissolves these enzymes, and through >osmosis the spores receive food that the enzymes have broken down to >liquid form. > >It just seems to me that the high indoor RH levels are condusive to >mold, but they don't really seem to cause food source to be wet >enough to 'germinate' spores. I can see humid air getting trapped in >drawers, closets, behind furniture and then when the air >conditioning runs, it creates localized condensation in these out of >the way places and starts the mold. > >I realize there are spores everywhere, but it does not seem like the >spores 'spontaneously germinate' from high relative humidities. From >what happend to me it looks like it needs a wet spot to get >established. > >I am good at designing to maintain conditions that prevent the >humidity levels condusive to mold, I am just looking for some >comments on all the experts in here on what makes the mold grow. >Does mold need a wet saturated food source to start growing? Quote Link to comment Share on other sites More sharing options...
Guest guest Posted July 18, 2005 Report Share Posted July 18, 2005 To re-hash this old thread. High humidity itself does not seem to cause mold. Condensation as a result of high humidity can. I base my opinion on observations of non-air conditioned homes in a humid tropical environment, where the only cooling available is opening windows to let the trade winds blow through and to run ceiling fans. Air with an 80F dew point blowing through, no mold. Even in older 'historical' homes. Air condition that home and maintain a temperature below the ambient dew point and you can run the risk of humid air condensating on a surface cooler than the ambient dewpoint. Wet spot could and will most likely start mold. Other observations are in the old thread below. Basically observations that a wet food source is needed, rather than spores grabbing moisture directly from the air at certain temperature/humidity levels. > > > Hello everyone. > > Certain temperature and humidity ranges are written as very > condusive to mold, but from a recent experience it seems like mold > needs a physically saturated food source to get started. > > My experience is from the effects of a hurricane. My home, a two > story town house, was flooded by storm surge however only 4 inches > made it inside and the ground floor has all concrete walls. > > It was a couple days after the storm before we could get back into > our home and we had to bleach the baseboard trim to kill visible > mold, and rather than take chances we bleached all the trim. > > I was without power for a month, and it typically averaged inside > close to 86F at 85% RH for three weeks, then when I managed to get a > small window AC unit running from my generator, it was a week of 83F > @ 68% RH. > > I did not get an explosion of mold in the upper levels with all that > sheet rock. > > My office is in an industrial 'butler' building and the high sea > water mark was 46 " . My ceiling is under a mezzanine and some roof > panels were lost in the storm and rain water was getting on the > mezzanine. > > My walls quickly 'molded' up to the high water mark, and a couple > days later the ceiling was showing mold as well. Both the walls and > the ceilings were wet. I was forced to gut this office. I will never > buy particle board book cases again either as they all collapsed. > > In both of these situations, with no power, there was no AC > operating and therefore there was nothing cooler than the ambient > dewpoint which howvers around 80F from June to the end of Novemeber. > > I was reading ASHRAE's Humidity COntrol Design Guide, Chapter 7, > http://www.masongrant.com/pdf/design_guide/ASHRAE_HCDG_C7_Mold.pdf > and it comments how spore cases seem to have enzymes on them. > Moisture in the food source dissolves these enzymes, and through > osmosis the spores receive food that the enzymes have broken down to > liquid form. > > It just seems to me that the high indoor RH levels are condusive to > mold, but they don't really seem to cause food source to be wet > enough to 'germinate' spores. I can see humid air getting trapped in > drawers, closets, behind furniture and then when the air > conditioning runs, it creates localized condensation in these out of > the way places and starts the mold. > > I realize there are spores everywhere, but it does not seem like the > spores 'spontaneously germinate' from high relative humidities. From > what happend to me it looks like it needs a wet spot to get > established. > > I am good at designing to maintain conditions that prevent the > humidity levels condusive to mold, I am just looking for some > comments on all the experts in here on what makes the mold grow. > Does mold need a wet saturated food source to start growing? Quote Link to comment Share on other sites More sharing options...
Guest guest Posted July 18, 2005 Report Share Posted July 18, 2005 A current project is a home that had about 5 feet of salt water in it last September. The rennovation is almost complete, and this home has been sitting under ambient conditions for ten months. This is a humid place, year round cooling, dewpoints in the low 70s in the winter, about 80 all summer. The exterior walls were concrete how ever the walls were firred with sheet rock which was ripped out immediately. Partiton walls are framed with pressure treated lumber and the second floor is TJIs. I can see leather in a drawer with humid air trapped in there, but I would be surprised to see it in the TJI's. Perhaps I should have them running a dehumidifier for a couple weeks or so, before they start up all the central air conditioning systems to help pull out mositure locked into the building materials, in particular the TJIs. This is a case of a resotration, but typical new construction homes here are exposed to high hunidity. Microlam beams and TJIs are not overly common here but they do exist. > > > > > > > > >Hello everyone. > > > > > >Certain temperature and humidity ranges are written as very > > >condusive to mold, but from a recent experience it seems like mold > > >needs a physically saturated food source to get started. > > > > > >My experience is from the effects of a hurricane. My home, a two > > >story town house, was flooded by storm surge however only 4 inches > > >made it inside and the ground floor has all concrete walls. > > > > > >It was a couple days after the storm before we could get back into > > >our home and we had to bleach the baseboard trim to kill visible > > >mold, and rather than take chances we bleached all the trim. > > > > > >I was without power for a month, and it typically averaged inside > > >close to 86F at 85% RH for three weeks, then when I managed to get > > a > > >small window AC unit running from my generator, it was a week of > > 83F > > >@ 68% RH. > > > > > >I did not get an explosion of mold in the upper levels with all > > that > > >sheet rock. > > > > > >My office is in an industrial 'butler' building and the high sea > > >water mark was 46 " . My ceiling is under a mezzanine and some roof > > >panels were lost in the storm and rain water was getting on the > > >mezzanine. > > > > > >My walls quickly 'molded' up to the high water mark, and a couple > > >days later the ceiling was showing mold as well. Both the walls > > and > > >the ceilings were wet. I was forced to gut this office. I will > > never > > >buy particle board book cases again either as they all collapsed. > > > > > >In both of these situations, with no power, there was no AC > > >operating and therefore there was nothing cooler than the ambient > > >dewpoint which howvers around 80F from June to the end of > > Novemeber. > > > > > >I was reading ASHRAE's Humidity COntrol Design Guide, Chapter 7, > > >http://www.masongrant.com/pdf/design_guide/ASHRAE_HCDG_C7_Mold.pdf > > >and it comments how spore cases seem to have enzymes on them. > > >Moisture in the food source dissolves these enzymes, and through > > >osmosis the spores receive food that the enzymes have broken down > > to > > >liquid form. > > > > > >It just seems to me that the high indoor RH levels are condusive > > to > > >mold, but they don't really seem to cause food source to be wet > > >enough to 'germinate' spores. I can see humid air getting trapped > > in > > >drawers, closets, behind furniture and then when the air > > >conditioning runs, it creates localized condensation in these out > > of > > >the way places and starts the mold. > > > > > >I realize there are spores everywhere, but it does not seem like > > the > > >spores 'spontaneously germinate' from high relative humidities. > > From > > >what happend to me it looks like it needs a wet spot to get > > >established. > > > > > >I am good at designing to maintain conditions that prevent the > > >humidity levels condusive to mold, I am just looking for some > > >comments on all the experts in here on what makes the mold grow. > > >Does mold need a wet saturated food source to start growing? > > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted July 18, 2005 Report Share Posted July 18, 2005 Any chance that these homes were vacated in the summer and were perhaps investigated in the fall or winter? Heating system set low to avoid freeze up but a lot cooler than human comfort zone? Moisture released in early fall causing some condensation perhaps? > I respectfully disagree. I've inspected many homes that have stood vacant > and closed up for extended periods of time and observed many Aspergillus > colonies on the ceilings and walls. > > Ed Gerhardt > Surelock Homes, Inc > Chapel Hill, NC Quote Link to comment Share on other sites More sharing options...
Guest guest Posted July 18, 2005 Report Share Posted July 18, 2005 Ed I do believe that it takes much longer to start mold growth when the RH is high, but condensation never takes place. It takes longer, but in time mold will often grow. The special case of houses that have been closed up for extended periods of time has the same problem that many cottages do; a ratcheting effect on indoor RH until it gets high enough to see some local condensation and then mold growth. Maybe not all moldy cottages see condensation, but there are so many hours at high RH that mold growth starts. I wish I could remember the name of the reference that I saw, courtesy of , that showed the time-RH plot of mold growth for many molds. If others would like to know about that maybe I will bother again and find the reference. Jim H. White SSAL Re: Re: Getting Mold Started I respectfully disagree. I've inspected many homes that have stood vacant and closed up for extended periods of time and observed many Aspergillus colonies on the ceilings and walls. Ed Gerhardt Surelock Homes, Inc Chapel Hill, NC Quote Link to comment Share on other sites More sharing options...
Guest guest Posted July 18, 2005 Report Share Posted July 18, 2005 Steve Well done! I forgot that some materials, especially those with complex physical surface shapes, can produce a local energy field that allows local , near surface RH to go well above the RH just a fraction of a mm above the surface. Carpet fibres produce such energy fields at the junction between two touching fibres and liquid water can form in that junction when the air RH is well below 100%. Jim H. White SSAL Re: Re: Getting Mold Started I agree that spores will not germinate in humid air alone. However, I have seen high humidity cause mold on hygroscopic surfaces many times -- without condensation. Examples are leather clothing items stored in a box or closet and certain engineered wood products (microlam girders and TJI joists). Moisture is chemically "captured" and held in sufficient amounts in the porous organic materials to germinate spores. There are plenty of instances where you can have a "wet food source" caused only by humid air without reaching the dew point.Steve Temes High humidity itself does not seem to cause mold. Condensation as a result of high humidity can.I base my opinion on observations of non-air conditioned homes in a humid tropical environment, where the only cooling available is opening windows to let the trade winds blow through and to run ceiling fans. Air with an 80F dew point blowing through, no mold. Even in older 'historical' homes.Air condition that home and maintain a temperature below the ambient dew point and you can run the risk of humid air condensating on a surface cooler than the ambient dewpoint. Wet spot could and will most likely start mold.Other observations are in the old thread below. Basically observations that a wet food source is needed, rather than spores grabbing moisture directly from the air at certain temperature/humidity levels. >>>Hello everyone.>>Certain temperature and humidity ranges are written as very >condusive to mold, but from a recent experience it seems like mold >needs a physically saturated food source to get started. >>My experience is from the effects of a hurricane. My home, a two >story town house, was flooded by storm surge however only 4 inches >made it inside and the ground floor has all concrete walls.>>It was a couple days after the storm before we could get back into >our home and we had to bleach the baseboard trim to kill visible >mold, and rather than take chances we bleached all the trim.>>I was without power for a month, and it typically averaged inside >close to 86F at 85% RH for three weeks, then when I managed to get a >small window AC unit running from my generator, it was a week of 83F >@ 68% RH.>>I did not get an explosion of mold in the upper levels with all that >sheet rock. >>My office is in an industrial 'butler' building and the high sea >water mark was 46". My ceiling is under a mezzanine and some roof >panels were lost in the storm and rain water was getting on the >mezzanine.>>My walls quickly 'molded' up to the high water mark, and a couple >days later the ceiling was showing mold as well. Both the walls and >the ceilings were wet. I was forced to gut this office. I will never >buy particle board book cases again either as they all collapsed.>>In both of these situations, with no power, there was no AC >operating and therefore there was nothing cooler than the ambient >dewpoint which howvers around 80F from June to the end of Novemeber.>>I was reading ASHRAE's Humidity COntrol Design Guide, Chapter 7, >http://www.masongrant.com/pdf/design_guide/ASHRAE_HCDG_C7_Mold.pdf>and it comments how spore cases seem to have enzymes on them. >Moisture in the food source dissolves these enzymes, and through >osmosis the spores receive food that the enzymes have broken down to >liquid form.>>It just seems to me that the high indoor RH levels are condusive to >mold, but they don't really seem to cause food source to be wet >enough to 'germinate' spores. I can see humid air getting trapped in >drawers, closets, behind furniture and then when the air >conditioning runs, it creates localized condensation in these out of >the way places and starts the mold.>>I realize there are spores everywhere, but it does not seem like the >spores 'spontaneously germinate' from high relative humidities. From >what happend to me it looks like it needs a wet spot to get >established.>>I am good at designing to maintain conditions that prevent the >humidity levels condusive to mold, I am just looking for some >comments on all the experts in here on what makes the mold grow. >Does mold need a wet saturated food source to start growing? Quote Link to comment Share on other sites More sharing options...
Guest guest Posted July 18, 2005 Report Share Posted July 18, 2005 Please remember that microorganisms don't care what the RH in the space might be. All they can " see " is the water activity level of the surface they occupy. Jim: a year or so back, you and I were both very excited about the release of a new text: " Microorganisms in Home and Indoor Work Environments - Diversity, Health Impacts, Investigation and Control " ; Editors: A. Samson, Flannigan, and J. . This wonderful book includes several plots that show both time to spore germination and the hyphal extension rate, versus water activity ( " a-subw " ) level [sorry, I can't make subscripts work properly on this list]. And for a few organisms, this info is presented at a couple of different temperatures. The Samson-Flannigan- text provides the cite to the origin of this data. As memory serves (without my copy of the text in front of me) the actual research was conducted and published in the 1950s. FYI: it appears that the publisher ( & Francis) has now made this text available in a variety of electronic formats; for more info, see: http://www.ebooksubscriptions.com/Home/html/moreinfo.asp? etailerid=19 & bookId=536901561 The answers you're looking for, Mr. " Arista Engineering " of Grand Cayman, and Mr. Gerhardt, et al, are in this book. BTW: PLEASE provide your name and affiliation if you're going to post on this listserv. Otherwise, we'll tease and cajole you mercilessly. And the answer is, no, liquid water is not required. An adequate a- subw for a sufficient period of time is required. It's as simple as that. But knowing what water activity really is, and how one determines a-subw from the room RH, or from the moisture content of a given material, is the tricky part, isn't it? Such knowledge requires multi-disciplinary studies! Combining the study of building science, engineering, applied microbiology, and industrial hygiene with a few more –ologies, is what makes this field of consulting SO INTERESTING, and so challenging. You have to work hard to pull it all together. So, get busy reading! Have fun. Wane <><><><><><><><><><><> Wane A. Baker, P.E., CIH Director, Air Quality Services MICHAELS ENGINEERING INC. " Real Professionals Providing Real Solutions " 811 Monitor Street, Suite 100 PO Box 2377 La Crosse, Wisconsin 54602 Phone , ext. 484 Cell Fax mailto:wab@... On the web at: http://www.michaelsengineering.com " To love what you do and feel that it matters - how could anything be more fun? " - Graham > Ed > I do believe that it takes much longer to start mold growth when the RH is high, but condensation never takes place. It takes longer, but in time mold will often grow. > > The special case of houses that have been closed up for extended periods of time has the same problem that many cottages do; a ratcheting effect on indoor RH until it gets high enough to see some local condensation and then mold growth. Maybe not all moldy cottages see condensation, but there are so many hours at high RH that mold growth starts. I wish I could remember the name of the reference that I saw, courtesy of , that showed the time- RH plot of mold growth for many molds. If others would like to know about that maybe I will bother again and find the reference. > Jim H. White SSAL > > Re: Re: Getting Mold Started > > > I respectfully disagree. I've inspected many homes that have stood vacant and closed up for extended periods of time and observed many Aspergillus colonies on the ceilings and walls. > > Ed Gerhardt > Surelock Homes, Inc > Chapel Hill, NC Quote Link to comment Share on other sites More sharing options...
Guest guest Posted July 18, 2005 Report Share Posted July 18, 2005 Jim, Thank you for your reply. I was thinking along those lines. I remind my clients that ask about mold that the mold is already there. It's the control of moisture and temperature, or the lack of, that starts its growth and appearance. I would be interested in 's time line, however, don't bother him only for me. Thanks again, Ed Gerhardt Quote Link to comment Share on other sites More sharing options...
Guest guest Posted July 19, 2005 Report Share Posted July 19, 2005 Unfortunately, when I arrive at one of these homes, there is no past history at hand. Some homes were minimally heated to prevent freezing pipes and some have been winterized with no services on at all. Some are foreclosures where past plumbing leaks and water damage went on unreported. Most times I have no idea how long the home has existed under these conditions. It is truly difficult inspecting a home in this condition, knowing a young family is purchasing the home, ,due to budget, which can significantly place young developing bodies at risk of permanent damage. Furthermore, perspective slum lords purchase these depressed, mold infected homes, give them a paint job and some new appliances and rent them out without consequence. Quote Link to comment Share on other sites More sharing options...
Guest guest Posted July 19, 2005 Report Share Posted July 19, 2005 Carnak, The term,water activity (Aw), is missing from the discussion. You do not need saturation for mold growth on building materials. 83% RH should support growth of xerophilic mold like various species of Aspergillus, Penicillium, Wallemia, etc. DG-18 has a Aw of approximately 0.93. The xerophiles grow within 1 week (sometimes 2 weeks - A. restictus) while the growth surface never reaches saturation. But, the higher temperature will slow the growth for some species. Look at the various lab books for mold (JI Pitt - " Fungi and Food Spoilage " ). Some species do not grow well at higher temperatures and some do. Aspergillus niger will do well and Penicillium roqueforti will not. Both are very common in the outdoor air. The pH of the growth surface may inhibit growth. Increasing the solute of the surface with bleach residue (P.U.) may cause the the Aw to go below 0.83 (assuming equilibrium in an 83% RH environment). Look at the difference between media like MEA and DG- 18. In the same vein is the amount of cellulose (sugar) versus lignan (fiber or structure). Solid wood trim has more lignan and holds more water which means the Aw is lower and requires longer growing times than paper-faced gypsum board, ceiling tiles or particle board (glue = high sugar or jelly for mold). Paints or primers may have metals/salts like titanium dioxide with the right elastomeric properties that does not trap water in the solid wood but does not let the titanium dioxide leach away. titanium dioxide is used for pigmentation in paints and primers on a regualr basis for those of you who insist on using or recommending bleach. Also, the amount of light (UV) may challenge growth (to a degree) versus the dark side on the backing of wallboard. Another variable is oxygen tension or air. Some organism need plenty of air an other need little. This is well established in food preservation by pumping CO2 in packaging to prevent spoilage. Have you ever seen Stachybotrys grow where the paper-faced gypsum meets the wall stud and other forms of mold will not grow? The nitrogen content of the growth surface is another consideration. If you clean with quaternary ammonium cleaners or disinfectants, you may have trouble when a residue develops. Some people like to deodorize with Lysol and create a real problem. Have you taken samples and tested for the ascospores of Penicillium and Aspergillus. Did the lab allow enough time to culture? I would expect to find these organisms in the environment you are describing. I do not think any mold you are missing is going to produce mycotoxins due to the low Aw. This does not mean the allergenic effect from proteins are not present. Your environment will produce mold. It is just a question of time and tide. One day, I am going to finish college so I can claim to be edumedicated like the rest of the professional world. I can say Aw is more complicated than most may think. Get out your psychrometric charts and get going with the other tools that read temperature, RH and MC along with a laser thermometer. Then consider the other variables listed above here. I will give you an area that has not been studied to my knowledge but the chemists should chime in if they know a source. We (or I with multiple personalities) do not know what effect rapid temperature changes (rising and falling) and subsequent pressure gradients (rising and falling) have on growth and mycotoxin production. If someone knows, I'm all ears. I think the ideal gas law has applications that have been largely overlooked by microbiologists/mycologists/biochemists similar to the IH crowd overlooking building science. Does anyone have an idle dynamic chamber and a few million dollars? Georgia State (D. Ahern / S. Crow) should have a lock on a goverment grant if the goverment would stop being tight-fisted with seeking truth that may create higher liability and building operation cost. Regards, Greg Weatherman " Certifiable Microbial Instigator " (unofficially Trade Marked) aerobioLogical Solutions Inc. Arlington VA 22202 gw@... ****************************************************** > > > > > > Hello everyone. > > > > Certain temperature and humidity ranges are written as very > > condusive to mold, but from a recent experience it seems like mold > > needs a physically saturated food source to get started. > > > > My experience is from the effects of a hurricane. My home, a two > > story town house, was flooded by storm surge however only 4 inches > > made it inside and the ground floor has all concrete walls. > > > > It was a couple days after the storm before we could get back into > > our home and we had to bleach the baseboard trim to kill visible > > mold, and rather than take chances we bleached all the trim. > > > > I was without power for a month, and it typically averaged inside > > close to 86F at 85% RH for three weeks, then when I managed to get > a > > small window AC unit running from my generator, it was a week of > 83F > > @ 68% RH. > > > > I did not get an explosion of mold in the upper levels with all > that > > sheet rock. > > > > My office is in an industrial 'butler' building and the high sea > > water mark was 46 " . My ceiling is under a mezzanine and some roof > > panels were lost in the storm and rain water was getting on the > > mezzanine. > > > > My walls quickly 'molded' up to the high water mark, and a couple > > days later the ceiling was showing mold as well. Both the walls > and > > the ceilings were wet. I was forced to gut this office. I will > never > > buy particle board book cases again either as they all collapsed. > > > > In both of these situations, with no power, there was no AC > > operating and therefore there was nothing cooler than the ambient > > dewpoint which howvers around 80F from June to the end of > Novemeber. > > > > I was reading ASHRAE's Humidity COntrol Design Guide, Chapter 7, > > http://www.masongrant.com/pdf/design_guide/ASHRAE_HCDG_C7_Mold.pdf > > and it comments how spore cases seem to have enzymes on them. > > Moisture in the food source dissolves these enzymes, and through > > osmosis the spores receive food that the enzymes have broken down > to > > liquid form. > > > > It just seems to me that the high indoor RH levels are condusive > to > > mold, but they don't really seem to cause food source to be wet > > enough to 'germinate' spores. I can see humid air getting trapped > in > > drawers, closets, behind furniture and then when the air > > conditioning runs, it creates localized condensation in these out > of > > the way places and starts the mold. > > > > I realize there are spores everywhere, but it does not seem like > the > > spores 'spontaneously germinate' from high relative humidities. > From > > what happend to me it looks like it needs a wet spot to get > > established. > > > > I am good at designing to maintain conditions that prevent the > > humidity levels condusive to mold, I am just looking for some > > comments on all the experts in here on what makes the mold grow. > > Does mold need a wet saturated food source to start growing? Quote Link to comment Share on other sites More sharing options...
Guest guest Posted July 19, 2005 Report Share Posted July 19, 2005 Cudos Wayne. All that effectively matters is the water activity (aw) at the interface. vapor pressure water in substrate aw = --------------------------------- vapor pressure of pure water Except perhaps in the case of Serpula lacrymans & Poria incrassata [dry rot] where the aw requirements are so low as to be negligible. Other factors are: Hydrogen ion concentration Temperature Nutrient status Specific solute effects Preservatives/inhibitors Gas tension of oxygen and carbon dioxide Tony .................................................. " Tony " Havics, CHMM, CIH, PE Executive Director of Technical Services QEPI 1611 South lin Road Indianapolis, IN 46239 Office: Ext 114 Fax: Cell: This message is from QEPI. This message and any attachments may contain legally privileged or confidential information, and are intended only for the individual or entity identified above as the addressee. If you are not the addressee, or if this message has been addressed to you in error, you are not authorized to read, copy, or distribute this message and any attachments, and we ask that you please delete this message and attachments (including all copies) and notify the sender by return e-mail or by phone at . Delivery of this message and any attachments to any person other than the intended recipient(s) is not intended in any way to waive confidentiality or a privilege. All personal messages express views only of the sender, which are not to be attributed to QEPI and may not be copied or distributed without this statement. Re: Getting Mold Started Please remember that microorganisms don't care what the RH in the space might be. All they can " see " is the water activity level of the surface they occupy. Jim: a year or so back, you and I were both very excited about the release of a new text: " Microorganisms in Home and Indoor Work Environments - Diversity, Health Impacts, Investigation and Control " ; Editors: A. Samson, Flannigan, and J. . This wonderful book includes several plots that show both time to spore germination and the hyphal extension rate, versus water activity ( " a-subw " ) level [sorry, I can't make subscripts work properly on this list]. And for a few organisms, this info is presented at a couple of different temperatures. The Samson-Flannigan- text provides the cite to the origin of this data. As memory serves (without my copy of the text in front of me) the actual research was conducted and published in the 1950s. FYI: it appears that the publisher ( & Francis) has now made this text available in a variety of electronic formats; for more info, see: http://www.ebooksubscriptions.com/Home/html/moreinfo.asp? etailerid=19 & bookId=536901561 The answers you're looking for, Mr. " Arista Engineering " of Grand Cayman, and Mr. Gerhardt, et al, are in this book. BTW: PLEASE provide your name and affiliation if you're going to post on this listserv. Otherwise, we'll tease and cajole you mercilessly. And the answer is, no, liquid water is not required. An adequate a- subw for a sufficient period of time is required. It's as simple as that. But knowing what water activity really is, and how one determines a-subw from the room RH, or from the moisture content of a given material, is the tricky part, isn't it? Such knowledge requires multi-disciplinary studies! Combining the study of building science, engineering, applied microbiology, and industrial hygiene with a few more -ologies, is what makes this field of consulting SO INTERESTING, and so challenging. You have to work hard to pull it all together. So, get busy reading! Have fun. Wane <><><><><><><><><><><> Wane A. Baker, P.E., CIH Director, Air Quality Services MICHAELS ENGINEERING INC. " Real Professionals Providing Real Solutions " 811 Monitor Street, Suite 100 PO Box 2377 La Crosse, Wisconsin 54602 Phone , ext. 484 Cell Fax mailto:wab@... On the web at: http://www.michaelsengineering.com " To love what you do and feel that it matters - how could anything be more fun? " - Graham > Ed > I do believe that it takes much longer to start mold growth when the RH is high, but condensation never takes place. It takes longer, but in time mold will often grow. > > The special case of houses that have been closed up for extended periods of time has the same problem that many cottages do; a ratcheting effect on indoor RH until it gets high enough to see some local condensation and then mold growth. Maybe not all moldy cottages see condensation, but there are so many hours at high RH that mold growth starts. I wish I could remember the name of the reference that I saw, courtesy of , that showed the time- RH plot of mold growth for many molds. If others would like to know about that maybe I will bother again and find the reference. > Jim H. White SSAL > > Re: Re: Getting Mold Started > > > I respectfully disagree. I've inspected many homes that have stood vacant and closed up for extended periods of time and observed many Aspergillus colonies on the ceilings and walls. > > Ed Gerhardt > Surelock Homes, Inc > Chapel Hill, NC FAIR USE NOTICE: This site contains copyrighted material the use of which has not always been specifically authorized by the copyright owner. We are making such material available in our efforts to advance understanding of environmental, political, human rights, economic, democracy, scientific, and social justice issues, etc. We believe this constitutes a 'fair use' of any such copyrighted material as provided for in section 107 of the US Copyright Law. In accordance with Title 17 U.S.C. Section 107, the material on this site is distributed without profit to those who have expressed a prior interest in receiving the included information for research and educational purposes. For more information go to: http://www.law.cornell.edu/uscode/17/107.shtml. 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Guest guest Posted July 19, 2005 Report Share Posted July 19, 2005 > FYI: it appears that the publisher ( & Francis) has now made > this text available in a variety of electronic formats; for more > info, see: > http://www.ebooksubscriptions.com/Home/html/moreinfo.asp? > etailerid=19 & bookId=536901561 Thanks for the book suggestion, I looked over the sample pades and it was mainly about spores/pollen in the air. I think I will gamble the fee to read the entire book. > The answers you're looking for, Mr. " Arista Engineering " of Grand > Cayman, and Mr. Gerhardt, et al, are in this book. > BTW: PLEASE provide your name and affiliation if you're going to > post on this listserv. Otherwise, we'll tease and cajole you > mercilessly. You must be either the moderator of this group or some one who did a search and found Arista Engineering, in amongst the credits for sound engineers for Arista Records. I have no intention of putting my name, phone number and address in my signature but here it is one time only. M u r r a y W o o d g a t e, P.Eng. A r i s t a Engineering Co.Ltd. Grand Cayman, Cayman Islands one three-four-5 525 twelve hundred I have dealt with four feet of snow and forty below zero for 37 years and have been dealing with a hot humid climate for the last 7. > And the answer is, no, liquid water is not required. An adequate a- > subw for a sufficient period of time is required. It's as simple as > that. But knowing what water activity really is, and how one > determines a-subw from the room RH, or from the moisture content of > a given material, is the tricky part, isn't it? Such knowledge > requires multi-disciplinary studies! > > Combining the study of building science, engineering, applied > microbiology, and industrial hygiene with a few more –ologies, is > what makes this field of consulting SO INTERESTING, and so > challenging. You have to work hard to pull it all together. > > So, get busy reading! > > Have fun. > > Wane > > <><><><><><><><><><><> > Wane A. Baker, P.E., CIH > Director, Air Quality Services > MICHAELS ENGINEERING INC. > " Real Professionals Providing Real Solutions " > 811 Monitor Street, Suite 100 > PO Box 2377 > La Crosse, Wisconsin 54602 > > Phone , ext. 484 > Cell > Fax > > mailto:wab@m... > On the web at: http://www.michaelsengineering.com > > " To love what you do and feel that it matters - how could anything > be more fun? " > - Graham > > > > Ed > > I do believe that it takes much longer to start mold growth when > the RH is high, but condensation never takes place. It takes longer, > but in time mold will often grow. > > > > The special case of houses that have been closed up for extended > periods of time has the same problem that many cottages do; a > ratcheting effect on indoor RH until it gets high enough to see some > local condensation and then mold growth. Maybe not all moldy > cottages see condensation, but there are so many hours at high RH > that mold growth starts. I wish I could remember the name of the > reference that I saw, courtesy of , that showed the time- > RH plot of mold growth for many molds. If others would like to know > about that maybe I will bother again and find the reference. > > Jim H. White SSAL > > > > Re: Re: Getting Mold Started > > > > > > I respectfully disagree. I've inspected many homes that have > stood vacant and closed up for extended periods of time and observed > many Aspergillus colonies on the ceilings and walls. > > > > Ed Gerhardt > > Surelock Homes, Inc > > Chapel Hill, NC Quote Link to comment Share on other sites More sharing options...
Guest guest Posted July 19, 2005 Report Share Posted July 19, 2005 > FYI: it appears that the publisher ( & Francis) has now made > this text available in a variety of electronic formats; for more > info, see: > http://www.ebooksubscriptions.com/Home/html/moreinfo.asp? > etailerid=19 & bookId=536901561 Thanks for the book suggestion, I looked over the sample pades and it was mainly about spores/pollen in the air. I think I will gamble the fee to read the entire book. > The answers you're looking for, Mr. " Arista Engineering " of Grand > Cayman, and Mr. Gerhardt, et al, are in this book. > BTW: PLEASE provide your name and affiliation if you're going to > post on this listserv. Otherwise, we'll tease and cajole you > mercilessly. You must be either the moderator of this group or some one who did a search and found Arista Engineering, in amongst the credits for sound engineers for Arista Records. I have no intention of putting my name, phone number and address in my signature but here it is one time only. M u r r a y W o o d g a t e, P.Eng. A r i s t a Engineering Co.Ltd. Grand Cayman, Cayman Islands one three-four-5 525 twelve hundred I have dealt with four feet of snow and forty below zero for 37 years and have been dealing with a hot humid climate for the last 7. > And the answer is, no, liquid water is not required. An adequate a- > subw for a sufficient period of time is required. It's as simple as > that. But knowing what water activity really is, and how one > determines a-subw from the room RH, or from the moisture content of > a given material, is the tricky part, isn't it? Such knowledge > requires multi-disciplinary studies! > > Combining the study of building science, engineering, applied > microbiology, and industrial hygiene with a few more –ologies, is > what makes this field of consulting SO INTERESTING, and so > challenging. You have to work hard to pull it all together. > > So, get busy reading! > > Have fun. > > Wane > > <><><><><><><><><><><> > Wane A. Baker, P.E., CIH > Director, Air Quality Services > MICHAELS ENGINEERING INC. > " Real Professionals Providing Real Solutions " > 811 Monitor Street, Suite 100 > PO Box 2377 > La Crosse, Wisconsin 54602 > > Phone , ext. 484 > Cell > Fax > > mailto:wab@m... > On the web at: http://www.michaelsengineering.com > > " To love what you do and feel that it matters - how could anything > be more fun? " > - Graham > > > > Ed > > I do believe that it takes much longer to start mold growth when > the RH is high, but condensation never takes place. It takes longer, > but in time mold will often grow. > > > > The special case of houses that have been closed up for extended > periods of time has the same problem that many cottages do; a > ratcheting effect on indoor RH until it gets high enough to see some > local condensation and then mold growth. Maybe not all moldy > cottages see condensation, but there are so many hours at high RH > that mold growth starts. I wish I could remember the name of the > reference that I saw, courtesy of , that showed the time- > RH plot of mold growth for many molds. If others would like to know > about that maybe I will bother again and find the reference. > > Jim H. White SSAL > > > > Re: Re: Getting Mold Started > > > > > > I respectfully disagree. I've inspected many homes that have > stood vacant and closed up for extended periods of time and observed > many Aspergillus colonies on the ceilings and walls. > > > > Ed Gerhardt > > Surelock Homes, Inc > > Chapel Hill, NC Quote Link to comment Share on other sites More sharing options...
Guest guest Posted July 19, 2005 Report Share Posted July 19, 2005 Toney: it's just " Wane " . the a-subw requirements of Serpula and Poria are not particularly low. what's unique about these wood rot organisms is the ability to transport water across considerable distances. they still require a source of moisture, and a surface at a-subw < 0.70 won't suffice. " gas tension " ? STILL just " Wane " > Cudos Wayne. > > All that effectively matters is the water activity (aw) at the > interface. > > vapor pressure water in substrate > aw = --------------------------------- > vapor pressure of pure water > > Except perhaps in the case of Serpula lacrymans & Poria incrassata [dry > rot] where the aw requirements are so low as to be negligible. > > Other factors are: > > Hydrogen ion concentration > Temperature > Nutrient status > Specific solute effects > Preservatives/inhibitors > Gas tension of oxygen and carbon dioxide > > > Tony > > ................................................. > " Tony " Havics, CHMM, CIH, PE > Executive Director of Technical Services > QEPI > 1611 South lin Road > Indianapolis, IN 46239 > Office: Ext 114 > Fax: > Cell: > > > Re: Getting Mold Started > > > Please remember that microorganisms don't care what the RH in the > space might be. All they can " see " is the water activity level of > the surface they occupy. > > Jim: a year or so back, you and I were both very excited about the > release of a new text: " Microorganisms in Home and Indoor Work > Environments - Diversity, Health Impacts, Investigation and > Control " ; Editors: A. Samson, Flannigan, and J. > . > > This wonderful book includes several plots that show both time to > spore germination and the hyphal extension rate, versus water > activity ( " a-subw " ) level [sorry, I can't make subscripts work > properly on this list]. And for a few organisms, this info is > presented at a couple of different temperatures. > > The Samson-Flannigan- text provides the cite to the origin of > this data. As memory serves (without my copy of the text in front > of me) the actual research was conducted and published in the > 1950s. > > FYI: it appears that the publisher ( & Francis) has now made > this text available in a variety of electronic formats; for more > info, see: > http://www.ebooksubscriptions.com/Home/html/moreinfo.asp? > etailerid=19 & bookId=536901561 > > The answers you're looking for, Mr. " Arista Engineering " of Grand > Cayman, and Mr. Gerhardt, et al, are in this book. > > BTW: PLEASE provide your name and affiliation if you're going to > post on this listserv. Otherwise, we'll tease and cajole you > mercilessly. > > And the answer is, no, liquid water is not required. An adequate a- > subw for a sufficient period of time is required. It's as simple as > that. But knowing what water activity really is, and how one > determines a-subw from the room RH, or from the moisture content of > a given material, is the tricky part, isn't it? Such knowledge > requires multi-disciplinary studies! > > Combining the study of building science, engineering, applied > microbiology, and industrial hygiene with a few more -ologies, is > what makes this field of consulting SO INTERESTING, and so > challenging. You have to work hard to pull it all together. > > So, get busy reading! > > Have fun. > > Wane > > <><><><><><><><><><><> > Wane A. Baker, P.E., CIH > Director, Air Quality Services > MICHAELS ENGINEERING INC. > " Real Professionals Providing Real Solutions " > 811 Monitor Street, Suite 100 > PO Box 2377 > La Crosse, Wisconsin 54602 > > Phone , ext. 484 > Cell > Fax > > mailto:wab@m... > On the web at: http://www.michaelsengineering.com > > " To love what you do and feel that it matters - how could anything > be more fun? " > - Graham > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted July 19, 2005 Report Share Posted July 19, 2005 Toney: it's just " Wane " . the a-subw requirements of Serpula and Poria are not particularly low. what's unique about these wood rot organisms is the ability to transport water across considerable distances. they still require a source of moisture, and a surface at a-subw < 0.70 won't suffice. " gas tension " ? STILL just " Wane " > Cudos Wayne. > > All that effectively matters is the water activity (aw) at the > interface. > > vapor pressure water in substrate > aw = --------------------------------- > vapor pressure of pure water > > Except perhaps in the case of Serpula lacrymans & Poria incrassata [dry > rot] where the aw requirements are so low as to be negligible. > > Other factors are: > > Hydrogen ion concentration > Temperature > Nutrient status > Specific solute effects > Preservatives/inhibitors > Gas tension of oxygen and carbon dioxide > > > Tony > > ................................................. > " Tony " Havics, CHMM, CIH, PE > Executive Director of Technical Services > QEPI > 1611 South lin Road > Indianapolis, IN 46239 > Office: Ext 114 > Fax: > Cell: > > > Re: Getting Mold Started > > > Please remember that microorganisms don't care what the RH in the > space might be. All they can " see " is the water activity level of > the surface they occupy. > > Jim: a year or so back, you and I were both very excited about the > release of a new text: " Microorganisms in Home and Indoor Work > Environments - Diversity, Health Impacts, Investigation and > Control " ; Editors: A. Samson, Flannigan, and J. > . > > This wonderful book includes several plots that show both time to > spore germination and the hyphal extension rate, versus water > activity ( " a-subw " ) level [sorry, I can't make subscripts work > properly on this list]. And for a few organisms, this info is > presented at a couple of different temperatures. > > The Samson-Flannigan- text provides the cite to the origin of > this data. As memory serves (without my copy of the text in front > of me) the actual research was conducted and published in the > 1950s. > > FYI: it appears that the publisher ( & Francis) has now made > this text available in a variety of electronic formats; for more > info, see: > http://www.ebooksubscriptions.com/Home/html/moreinfo.asp? > etailerid=19 & bookId=536901561 > > The answers you're looking for, Mr. " Arista Engineering " of Grand > Cayman, and Mr. Gerhardt, et al, are in this book. > > BTW: PLEASE provide your name and affiliation if you're going to > post on this listserv. Otherwise, we'll tease and cajole you > mercilessly. > > And the answer is, no, liquid water is not required. An adequate a- > subw for a sufficient period of time is required. It's as simple as > that. But knowing what water activity really is, and how one > determines a-subw from the room RH, or from the moisture content of > a given material, is the tricky part, isn't it? Such knowledge > requires multi-disciplinary studies! > > Combining the study of building science, engineering, applied > microbiology, and industrial hygiene with a few more -ologies, is > what makes this field of consulting SO INTERESTING, and so > challenging. You have to work hard to pull it all together. > > So, get busy reading! > > Have fun. > > Wane > > <><><><><><><><><><><> > Wane A. Baker, P.E., CIH > Director, Air Quality Services > MICHAELS ENGINEERING INC. > " Real Professionals Providing Real Solutions " > 811 Monitor Street, Suite 100 > PO Box 2377 > La Crosse, Wisconsin 54602 > > Phone , ext. 484 > Cell > Fax > > mailto:wab@m... > On the web at: http://www.michaelsengineering.com > > " To love what you do and feel that it matters - how could anything > be more fun? " > - Graham > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted July 19, 2005 Report Share Posted July 19, 2005 Hi Mr. Woodgate: Our careers in engineering are generally comparable, although I'm sure my current location cannot compare with the Caymans. (well, it could be a toss-up) The info on your whereabouts is in your Yahoo ID, sir -- nothing more mysterious than that. I am not moderator of this forum, but it appears that you may be new to this group. As a matter of courtesy, and as acknowledgement of the source of claims that any one of us might make, many of those who are active in the group have expressed distain and distrust for those who hide behind pseudonyms. We've had far too many persons with one agenda or another attempt to sway the uninitiated. Look through the archives; you'll find that nothing personal was intended by my request on behalf of the group. If you're worried about being spammed as a result of your participation, it's already too late. Your n a m e and e m a i l a d d r e s s are easy to derive from this list. =) As an engineer, I suspect you've seen your share; perhaps you've seen it all! Your studies in applied microbiology and building science, however, may benefit from additional study. This group is a great place to seek help. The Samson text provides a terrific source of guidance on much more than spores in the air; keep reading. I can also highly recommend Bill Rose's new text, " Water in Buildings: An Architect's Guide to Moisture and Mold " . A splendid discussion, with just the right mix of humor and theory, from the perspective of a research architect who's been studying damp buildings for decades. Enjoy! with kind regards, Wane <><><><><><><><><><><> Wane A. Baker, P.E., CIH Director, Air Quality Services MICHAELS ENGINEERING INC. " Real Professionals Providing Real Solutions " 811 Monitor Street, Suite 100 PO Box 2377 La Crosse, Wisconsin 54602 Phone , ext. 484 Cell Fax mailto:wab@... On the web at: http://www.michaelsengineering.com " To love what you do and feel that it matters - how could anything be more fun? " - Graham > > > FYI: it appears that the publisher ( & Francis) has now made > > this text available in a variety of electronic formats; for more > > info, see: > > http://www.ebooksubscriptions.com/Home/html/moreinfo.asp? > > etailerid=19 & bookId=536901561 > > Thanks for the book suggestion, I looked over the sample pades and > it was mainly about spores/pollen in the air. I think I will gamble > the fee to read the entire book. > > > The answers you're looking for, Mr. " Arista Engineering " of Grand > > Cayman, and Mr. Gerhardt, et al, are in this book. > > > BTW: PLEASE provide your name and affiliation if you're going to > > post on this listserv. Otherwise, we'll tease and cajole you > > mercilessly. > > You must be either the moderator of this group or some one who did a > search and found Arista Engineering, in amongst the credits for > sound engineers for Arista Records. > > I have no intention of putting my name, phone number and address in > my signature but here it is one time only. > > M u r r a y W o o d g a t e, P.Eng. > A r i s t a Engineering Co.Ltd. > Grand Cayman, Cayman Islands > one three-four-5 525 twelve hundred > > I have dealt with four feet of snow and forty below zero for 37 > years and have been dealing with a hot humid climate for the last 7. Quote Link to comment Share on other sites More sharing options...
Guest guest Posted July 20, 2005 Report Share Posted July 20, 2005 Mr. Baker I have seen a fair bit, a cold dry climate north of Wisconsin, and seven years of a hot humid climate. I joined this group last year as soon as my internet connection was restored after we were hit by Hurricane Ivan as a Cat 5 storm. I lost my entire library at work and I am slowly rebuilding it. For years I have posted as Abby Normal, a great name if you ask me, and Abby gets all the spam. I also do not have the luxury of free speech, like I had in Canada. I could sure use an eductaion in microbiology, and this was my main reason for searching out a group like this. Do not be angry if I have a devil's advocate approach to mold, its just that I have seen quite a bit of conditions that should just be ripe for mold and it does not always appear, especially in non-air conditioned homes. Usually when one attends seminars, there are visual presentations and there is always the one slide, a prime example of 'how not to do it', which makes every one in attendance laugh. They are humourous, but I see these things on a routine basis. My only hard copy reference on mold is what is contained in ASHRAE's Humidity Control Design guide, which the author, a member of this group, sent me a FREE replacement as hurricane relief. I appreciate your reading lists. > > > > > FYI: it appears that the publisher ( & Francis) has now > made > > > this text available in a variety of electronic formats; for more > > > info, see: > > > http://www.ebooksubscriptions.com/Home/html/moreinfo.asp? > > > etailerid=19 & bookId=536901561 > > > > Thanks for the book suggestion, I looked over the sample pades and > > it was mainly about spores/pollen in the air. I think I will > gamble > > the fee to read the entire book. > > > > > The answers you're looking for, Mr. " Arista Engineering " of > Grand > > > Cayman, and Mr. Gerhardt, et al, are in this book. > > > > > BTW: PLEASE provide your name and affiliation if you're going > to > > > post on this listserv. Otherwise, we'll tease and cajole you > > > mercilessly. > > > > You must be either the moderator of this group or some one who did > a > > search and found Arista Engineering, in amongst the credits for > > sound engineers for Arista Records. > > > > I have no intention of putting my name, phone number and address > in > > my signature but here it is one time only. > > > > M u r r a y W o o d g a t e, P.Eng. > > A r i s t a Engineering Co.Ltd. > > Grand Cayman, Cayman Islands > > one three-four-5 525 twelve hundred > > > > I have dealt with four feet of snow and forty below zero for 37 > > years and have been dealing with a hot humid climate for the last > 7. Quote Link to comment Share on other sites More sharing options...
Guest guest Posted July 20, 2005 Report Share Posted July 20, 2005 Mr. Murray-Abby Normal-Woodgate: :-0 Lew Harriman's text is VERY good, and he does generally lurk on this list. (Hi, Lew!) unfortunately, it's not real strong on the fungi (sorry, Lew). for example, in the fourth illustration of " Stages of Mold Growth " on p. 102, the caption states: " The mold grows conidia, which generate and release spores to the air. " the description is in error here: conidia ARE the spores! the reproductive structures are called conidiophores. these terms are applicable to most of the Deuteromycota (Deuteromycotina, Deuteromycetes, sometimes Fungi Imperfecti) that are so common in water-damaged indoor surfaces -- what many of us simply call mold or microfungi. again, I do think very highly of the Harriman text, and have had the privilege of serving as faculty for the ASHRAE Learning Institute course " Humidity Control in Commercial Buildings " . an important topic, and fun stuff! sorry to hear about your encounter with Ivan; and not surprised that Mr. Harriman was so generous as to send a replacement copy. please let us know how we can continue to assist your quest. this function, IMHO, is the essence of this listserv. respectfully, Wane > > > > > > > FYI: it appears that the publisher ( & Francis) has now > > made > > > > this text available in a variety of electronic formats; for > more > > > > info, see: > > > > http://www.ebooksubscriptions.com/Home/html/moreinfo.asp? > > > > etailerid=19 & bookId=536901561 > > > > > > Thanks for the book suggestion, I looked over the sample pades > and > > > it was mainly about spores/pollen in the air. I think I will > > gamble > > > the fee to read the entire book. > > > > > > > The answers you're looking for, Mr. " Arista Engineering " of > > Grand > > > > Cayman, and Mr. Gerhardt, et al, are in this book. > > > > > > > BTW: PLEASE provide your name and affiliation if you're going > > to > > > > post on this listserv. Otherwise, we'll tease and cajole you > > > > mercilessly. > > > > > > You must be either the moderator of this group or some one who > did > > a > > > search and found Arista Engineering, in amongst the credits for > > > sound engineers for Arista Records. > > > > > > I have no intention of putting my name, phone number and address > > in > > > my signature but here it is one time only. > > > > > > M u r r a y W o o d g a t e, P.Eng. > > > A r i s t a Engineering Co.Ltd. > > > Grand Cayman, Cayman Islands > > > one three-four-5 525 twelve hundred > > > > > > I have dealt with four feet of snow and forty below zero for 37 > > > years and have been dealing with a hot humid climate for the > last > > 7. Quote Link to comment Share on other sites More sharing options...
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