Re: efficacy of germicidal UV

[Guest guest]

Given the initial installation cost for U.V., plus the annual lamp replacement

cost, wouldn't it be cheaper but just as effective to simply have your HVAC

inspected, cleaned, and otherwise serviced each year? Only it seems very few

people will spend the money for the annual service, unless they have a sizable

chunk of money tied up in some " special treatment system " .

Curtis Redington, RS

Environmental Quality Specialist

City of Wichita Dept. of Environmental Health

Wichita, KS

Re: efficacy of germicidal UV

Mike,

I am not arguing that UV isn't germicidal, but without a clean system to

begin with, and efficient filtration (minimum MERV 6-8, preferably MERV 11)

in place to keep the linings and coil clean, UV is worthless.

And few installers take the care that you seem to; based on the

installations I've seen, most just pop a lamp in someplace and walk off with

the exorbitant fee.

For the money, I'd spend on cleaning and filtration before UV irradiation.

C. May

May Indoor Air Investigations LLC

1522 Cambridge Street

Cambridge, MA 02139

www.mayindoorair.com

www.myhouseiskillingme.com

Geyer writes:

> :

>

> I, for one, believe the science behind UV irradiation as a germicidal method

> is very sound. I have seen (by my measurements) a tremendous reduction in

> active colony forming units inside HVAC systems (e.g., duct work, heat

> exchangers, fan blades, etc.) when UV lamps are installed. There was one

> negative comment recently about " UV killing spores whizzing by. " I for one

> believe it does work, although, like any engineering control, there are

> limitations. If the air speed (velocity) is really high and the UV lamp

> energy is low, there is a significant reduction in effect. If poorly

> designed/installed, the benefits of UV irradiation can be negligible. The

> lamps I have installed in HVAC systems are REALLY strong and warrant LOTO

> controls so they are not energized when the HVAC system is worked on, or if

> filters are changed. Moreover, they are shielded on the upstream side so

> debris/particulates do not impact and soil the bulbs. I usually place the

> lamps 4 to 6 inches from the heat exchanger (HE) on the upwind side, and

> rarely am I installing less than three lamps. I don't like placing them in

> dirty HVAC systems and when I install them on a retrofit, it is after the

> system is thoroughly cleaned. In side by side comparisons, i.e., HEs with

> lamps versus HEs without lamps, the cleanliness of the HEs with lamps could

> be easily seen one year later. In fact, the HEs (with lamps) looked as

> clean as the day the lamps were installed, while the other HEs had visible

> dirt on them. There is a lot to designing and installing UV systems in HVAC

> systems to make them effective - it is NOT a plug-n-play control. I know

> Kaiser Permanente has invested heavily in UV irradiation of their HVAC

> systems in an effort to control infection. I believe their results are

> really supportive of UV irradiation. A big advantage of UV irradiation is

> the low cost to operate. A big disadvantage is the high cost of each (good

> quality) bulb, and several bulbs are needed in each fan unit on small

> package units. On buildings with a centralized HVAC system (versus

> individual roof-mounted package units) there could be 20 to 30 bulbs, or

> more. Moreover, the HVAC fan unit must be so located that is can be easily

> serviced (not a problem with centralized HVAC systems). This is not the

> case in most residential construction because most architects/contractors

> design and place the fan unit in the attic...a very convenient but really

> dumb place to put a piece of machinery that needs periodic service with

> filters that warrant frequent replacing.

>

> If I had a house that had central air (I don't, we open windows) I would

> install UV irradiation along with an appropriate, well-sealed, HPFF filter

> bank; and it would deliver the cleanest air at the best, and lowest,

> operating cost. I am a believer in UV.

>

> For what it is worth...

> --

> Geyer, PE, CIH, CSP

> President

> KENTEC Industries, Inc.

> Bakersfield, California

> www.kerntecindustries.com

>

>

>

>

>

>

>

>> Hi all,

>>

>> Not too long ago, AirwaysEnv@... wrote:

>>

>>> Unfortunately, science and scientists do not exist outside of

>>> economics and finance. It can be seen in the way new technologies

>>> are marketed today that the line between science and marketing gets

>>> fuzzier and fuzzier. How about all these pharmaceutical

>>> advertisements on television today? Or ozone generating air

>>> purifiers. Or the science behind UV light bulbs in ducts to kill

>>> mold spores whizzing by...

>>

>> I thought that the science behind germicidal UV was sound. Anyone have

>> any thoughts on the matter?

>>

>> Thanks,

>>

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.

[Guest guest]

Steve,

It is the intensity of the UV that kills the bacteria and mold. I don't

recall the exact numbers but UV biosafety hood lights are about 100 or

more times more intense than sun light.

Bob

[Guest guest]

Curtis,

Are you speaking of those media filters that are normally replaced every monthly??

Ken Gibala

=====================

RE: Re: efficacy of germicidal UV

Just a note of caution from experience - U.V. lamps installed in such a manner as to expose media filters to the light will cause a rapid disintegration of the filter material. Curtis Redington, RSEnvironmental Quality SpecialistCity of Wichita Dept. of Environmental HealthWichita, KS-----Original Message-----From: iequality [mailto:iequality ]OnBehalf Of Jeff MaySent: Friday, April 07, 2006 6:54 PMTo: iequality Subject: Re: efficacy of germicidal UV, I posted this when the study came out: In a recent paper, "Effect of ultraviolet germicidal lights in office ventilation systems on workers' health and well-being: double-blind multiple crossover trial," (Lancet 2003; 362: 1785-91), the authors Menzies et.al. concluded that "installation of UVGI in most North American offices could resolve work-related symptoms in about 4 million employees, caused by microbial contamination of the heating, ventilation and air-conditioning systems." Despite the fact that ultraviolet germicidal irradiation (UVGI) has been shown in many previous studies to reduce airborne contagion, I believe that the conclusion of this study overstates the impact of UVGI on HVAC systems and office indoor air quality. Three healthy, well-ventilated (peak values of carbon dioxide were under 620 ppm) office buildings in Montreal, Canada were evaluated over the course of one year (July 1999 to July 2000). In the study, UV lamps (245-266 nm wavelength band), rated at 450 mW/cm2 at a distance of one meter, were mounted with reflectors 15 to 74 cm from the cooling coils and drip pans. At this level of irradiation (greater than what is typical), the authors estimated that the survival time for resistant organisms would be less than 4 minutes. Within the HVAC system, the UVGI lamps were cycled, operating for 12 weeks off, and then 4 consecutive weeks on. Questionnaires were repeatedly distributed to about 800 office workers to obtain subjective opinions regarding environmental satisfaction and allergy symptoms (categories included systemic, mucosal, respiratory, musculo-skeletal, and "any symptom") during the different time intervals. The concentration of microbes on the coils and in the drip pans was determined by placing sterile 5 cm x 5 cm "coupons" of sheet metal on the surfaces (exposed directly to the UVGI), and then placing the exposed coupons on a Petri dish containing culture media (Sabouraud or MEA), and incubating the dishes. Coupons (receiving no UVGI) were also placed on the filters. Air samples indoors and outdoors were obtained with Burkard volumetric air samplers (with Petri dishes) to determine the concentration of fungal spores. A total of 1240 samples were assayed. Endotoxin concentrations were determined using volumetric sampling and polycarbonate filter cassettes for the air, and by washings directly from the dust impacted on the coupon surfaces. A total of 284 samples were assayed. Airborne endotoxin was not detectable at workstations with the UVGI either on or off and there was a slight increase in levels on the filter coupons with the UVGI on. The amount of endotoxin on the coil coupon dropped from 8 endotoxin units (EU) to zero with the UVGI on. Culturable air samples for fungal spores at both the returns and supplies, with the UVGI both on and off, were 0 (zero) cfu/m3. The number of culturable spores per 25 cm2 on all coupons was very low, and averaged at the cooling coil from 0 (UVGI on) to about 4 (UVGI off) or far less than one spore per cm2 after a 4- or 12-week exposure period. The coupons on the filters collected 3 cfu/coupon (UVGI off) and 2 cfu/coupon (UVGI on). The coupons may not have been very efficient collectors since they lacked a "sticky" coating and were positioned perpendicular to the air flows and thus obstructed the stream lines. In addition, the irradiated coupons were exposed directly to the UVGI, whereas microbes on an actual HVAC surface would have received incident light at a variety of angles, the intensity of which would be attenuated by the dust accumulations. The data and results for different seasons were not separated. Since in Montreal there is a long heating season and a short cooling season, the expected results for each season should be quite different. In addition, during the heating season there is no condensation of moisture to promote microbial growth. In fact, in the presence of minimal dust on the coupons and few organisms, and without moisture, there is little opportunity for any microbial amplification, either in the heating or cooling season. Despite the reported reduction in symptoms indoors at work during the UVGI-on periods, no statistically significant differences were reported in the indoor air concentrations of microbes at work stations; thus the authors were left with no explanation for the reported reduction in symptoms associated with UVGI. (The authors postulated that the UVGI radiation may have somehow reduced the aerosolization of microbial antigenic proteins.) To prevent microbial growth due to moisture or high relative humidity in HVAC systems, the most important components of hygiene will always be proper design to begin with, adequate filtration (a minimum of MERV 6-8), and regular maintenance. Though UVGI may certainly serve as an adjunct in disinfecting exposed air and reducing microbial growth on irradiated surfaces, the impact on overall indoor air quality of UVGI alone should not be overstated. C. MayMay Indoor Air Investigations LLC1522 Cambridge StreetCambridge, MA 02139www.mayindoorair.comwww.myhouseiskillingme.com

[Guest guest]

Regarding:

BTW I see no TLV or BEI listed for hydro peroxide radicals or for O4, O5, or O6 in the workplace atmosphere. Might that be because there is no known hazard for these oxidizers?

I would say no. That is not the case. They are not exactly production chemicals or gases. That avoids the TSCA requirements for testing and reporting. Just because it isn't tested, doesn't make it safe. Same goes for "natural" compounds.

Tony

........................................................................... "Tony" Havics, CHMM, CIH, PEpH2, LLCPO Box 34140Indianapolis, IN 46234 cell90% of Risk Management is knowing where to place the decimal point...any consultant can give you the other 10%â„ This message is from pH2. 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 pH2 and may not be copied or distributed without this statement.

-----Original Message-----From: iequality [mailto:iequality ] On Behalf Of kengib .Sent: Saturday, April 08, 2006 9:38 PMTo: iequality Subject: Re: Re: efficacy of germicidal UV

Tony Havics,

Please help me. I'm confused why you are mentioning the TLV allowance for UV radiation.

Aren't we speaking about a UV bulb totally enclosed in an air duct?? Where does employee safety become a concern if the installation is totally enclosed and requires an electrical interlock and if the duct works are properly labeled and the maintenance personal are educated in the nature of the installation??

I am of the opinion there need be no safety hazard with proper electrical interlocks and safety labeling.

I agree your statement that "UV is a matter of residence time of the agent in relation to the radiation source" is true but only where the germicidal instrument is the UV bulb.

However where the UV bulb is used simply as an energy source to produce a fume of hydro peroxide radicals at a catalytic target there is an entirely different equation and residence time seems of no consequence.

Also let's not forget humidity is equally a prime factor in the killing success of the system where UV is used to generate advanced oxidizers.

BTW I see no TLV or BEI listed for hydro peroxide radicals or for O4, O5, or O6 in the workplace atmosphere. Might that be because there is no known hazard for these oxidizers?

Ken Gibala

RE: Re: efficacy of germicidal UV

Interesting.See comments below plus: UV exposure should be down around 1 mW/cm2 (see ACGIH TLV on UV by wavelength)

Tony......................................................................... "Tony" Havics, CHMM, CIH, PEpH2, LLCPO Box 34140Indianapolis, IN 46234 cell90% of Risk Management is knowing where to place the decimal point...any consultant can give you the other 10%â„ This message is from pH2. 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 pH2 and may not be copied or distributed without this statement.-----Original Message-----From: iequality [mailto:iequality ] On Behalf Of Jeff MaySent: Friday, April 07, 2006 6:54 PMTo: iequality Subject: Re: efficacy of germicidal UV,I posted this when the study came out:In a recent paper, “Effect of ultraviolet germicidal lights in officeventilation systems on workers’ health and well-being: double-blind multiplecrossover trial,†(Lancet 2003; 362: 1785-91), the authors Menzies et.al.concluded that “installation of UVGI in most North American offices couldresolve work-related symptoms in about 4 million employees, caused bymicrobial contamination of the heating, ventilation and air-conditioningsystems.â€Despite the fact that ultraviolet germicidal irradiation (UVGI) has beenshown in many previous studies to reduce airborne contagion, I believe thatthe conclusion of this study overstates the impact of UVGI on HVAC systemsand office indoor air quality. (Agree)Three healthy, well-ventilated (peak values of carbon dioxide were under 620ppm) office buildings in Montreal, Canada were evaluated over the course ofone year (July 1999 to July 2000). In the study, UV lamps (245-266 nmwavelength band), rated at 450 mW/cm2 at a distance of one meter, weremounted with reflectors 15 to 74 cm from the cooling coils and drip pans. Atthis level of irradiation (greater than what is typical - no kidding - Hart , back in 1942 noted that a kill rate of >99% at 3 min for 30 mW/cm2 at the surface), the authorsestimated that the survival time for resistant organisms would be less than4 minutes. Within the HVAC system, the UVGI lamps were cycled, operating for12 weeks off, and then 4 consecutive weeks on. Questionnaires wererepeatedly distributed to about 800 office workers to obtain subjectiveopinions regarding environmental satisfaction and allergy symptoms(categories included systemic, mucosal, respiratory, musculo-skeletal, and“any symptomâ€) during the different time intervals.The concentration of microbes on the coils and in the drip pans wasdetermined by placing sterile 5 cm x 5 cm “coupons†of sheet metal on thesurfaces (exposed directly to the UVGI), and then placing the exposedcoupons on a Petri dish containing culture media (Sabouraud or MEA), andincubating the dishes. Coupons (receiving no UVGI) were also placed on thefilters. Air samples indoors and outdoors were obtained with Burkardvolumetric air samplers (with Petri dishes) to determine the concentrationof fungal spores. A total of 1240 samples were assayed.Endotoxin concentrations were determined using volumetric sampling andpolycarbonate filter cassettes for the air, and by washings directly fromthe dust impacted on the coupon surfaces. A total of 284 samples wereassayed. Airborne endotoxin was not detectable at workstations with the UVGIeither on or off and there was a slight increase in levels on the filtercoupons with the UVGI on. The amount of endotoxin on the coil coupon droppedfrom 8 endotoxin units (EU) to zero with the UVGI on.Culturable air samples for fungal spores at both the returns and supplies,with the UVGI both on and off, were 0 (zero) cfu/m3. The number ofculturable spores per 25 cm2 on all coupons was very low, and averaged atthe cooling coil from 0 (UVGI on) to about 4 (UVGI off) or far less than onespore per cm2 after a 4- or 12-week exposure period. The coupons on thefilters collected 3 cfu/coupon (UVGI off) and 2 cfu/coupon (UVGI on). Thecoupons may not have been very efficient collectors since they lacked a“sticky†coating and were positioned perpendicular to the air flows and thusobstructed the stream lines. In addition, the irradiated coupons wereexposed directly to the UVGI, whereas microbes on an actual HVAC surfacewould have received incident light at a variety of angles, the intensity ofwhich would be attenuated by the dust accumulations.The data and results for different seasons were not separated. Since inMontreal there is a long heating season and a short cooling season, theexpected results for each season should be quite different. In addition,during the heating season there is no condensation of moisture to promotemicrobial growth. In fact, in the presence of minimal dust on the couponsand few organisms, and without moisture, there is little opportunity for anymicrobial amplification, either in the heating or cooling season.Despite the reported reduction in symptoms indoors at work during theUVGI-on periods, no statistically significant differences were reported inthe indoor air concentrations of microbes at work stations; thus the authorswere left with no explanation for the reported reduction in symptomsassociated with UVGI. (The authors postulated that the UVGI radiation mayhave somehow reduced the aerosolization of microbial antigenic proteins.)Suggests to me that if you operate the building the way is was designed and you perform operations & maintanence (O & M) correctly that you won't have problem. Thus, UV is for poorly maintained places??

Clearly, UV is a matter of residence time of the agent in relation to the radiation source. Although minimizing the amount on the coil to minimize aerosolization makes sense, it ignores the total volume and residence time of any aerosols already airborne (that may or may not be impacted on the coils) thus it ignores probability of desctruction (dose-response thing) and dilution.

Having said that, it has been show as far back as 1935 that UV can reduce infections in high occupancy spaces (hospitals and even school rooms [Wells, Wells, and Wilder: Experimental Control of Epidemic Spread of Contagion. 1942 for 3 schools]. [incidentally UV can work on fungi in certain circumstances] The factors are plenty and some could be arranged:

Sensitivity of population (general, babies, health adults, immune or adversely affected; it has been shown that pre-Ozone exposure can increase risk of infection, as can other infectionious agents immediately prior, e.g, infuenza prior to a bacterial challenge)

Agent(s) of concern

HVAC filtration

Air Changes per Hour (ACH) nominal and source

Recirculation amount and type (open air plenum vs returns)

Local ventilation supply (dilivery and patterns of movement into breating zone)

Velocity of air delivery (settling time in ducts and residence time of airbiorne bioaerosols past UV)

Occupation density (distance of transmission person-to-person, frequency of transmission to air, bioarosol agent generation rate, generation rate of secondary carriers (skin flakes for instance))

Building materials (static pull, carpeting as a sink, water resisitance of materials to lower surface RH and lower survival rate; internally lined Fiberglass)

Building environment (RH, Temp - functional relation to bioaerosol survival rates and human susceptibility [dryness on asthma, respiratory infections, etc.]; combustion sources)

Location of UV unit, intensity of source, wavelength

To prevent microbial growth due to moisture or high relative humidity inHVAC systems, the most important components of hygiene will always be properdesign to begin with, adequate filtration (a minimum of MERV 6-8), andregular maintenance. [Excellent points] Though UVGI may certainly serve as an adjunct indisinfecting exposed air and reducing microbial growth on irradiatedsurfaces, the impact on overall indoor air quality of UVGI alone should notbe overstated.[Well put] C. MayMay Indoor Air Investigations LLC1522 Cambridge StreetCambridge, MA 02139www.mayindoorair.comwww.myhouseiskillingme.comiamnotanairhead writes:> Hi all,>> Not too long ago, AirwaysEnv@... wrote:>>>Unfortunately, science and scientists do not exist outside of>> economics and finance. It can be seen in the way new technologies>>are marketed today that the line between science and marketing gets>> fuzzier and fuzzier. How about all these pharmaceutical>> advertisements on television today? Or ozone generating air>> purifiers. Or the science behind UV light bulbs in ducts to kill>>mold spores whizzing by...>> I thought that the science behind germicidal UV was sound. Anyone have> any thoughts on the matter?>> Thanks,> 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.

[Guest guest]

Steve:

Answer to Question: Because the energy from the sun (in watts per square centimeter) is several of orders of magnitude less than that produced by a good quality UV bulb (10,000 times less). UV irradiation typically has a “kill zone” of only several inches from the bulb, however, the harmful effects are much broader; hence the need for interlocks and LOTO. Another method of generating UV energy that has a much broader kill zone is via a plasma arc, however, there are other negative side affects of plasma energy (e.g., ozone) that must be controlled if used in an indoor environment.

--

Geyer, PE, CIH, CSP

President

KENTEC Industries, Inc.

Bakersfield, California

www.kerntecindustries.com

There was one negative comment recently about " UV killing spores whizzing by. " I for one believe it does work, although, like any engineering control, there are

limitations. If the air speed (velocity) is really high and the UV lamp

energy is low, there is a significant reduction in effect. If poorly

designed/installed, the benefits of UV irradiation can be negligible.

Question: Why doesn't UV from the sun kill mold spores floating around outdoors on a bright, sunny day? I've had some very high outdoor counts in sunny, summer weather.

Steve Temes

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.

[Guest guest]

The situation I observed involved deep pleat filters (e.g., "Space Guard" or "Air Bear") that are typically replaced annually. The U.V. light deteriorated the filters very quickly. Huge holes in the filter(s) within only a week or two. HVAC company's customer was very particular - that's why the money was spent on U.V. lights, by-pass HEPA unit, etc. As you can imagine, the customer was not happy about filter fibers blown all over the house. Although the HVAC company is usually very good, someone goofed up and installed the U.V. lights within line-of-sight of the filters (on both of the two systems in the home). The same reasons that U.V. may have useful applications for reducing microbial growth, slime formation, etc also means you've got to use it appropriately or you can make things worse (but isn't that true for a lot of thing?). In this case, the clean up costs alone exceeded $1,500.

Curtis

-----Original Message-----From: iequality [mailto:iequality ]On Behalf Of kengib .Sent: Monday, April 10, 2006 10:19 AMTo: iequality Subject: Re: Re: efficacy of germicidal UV

Curtis,

Are you speaking of those media filters that are normally replaced every monthly??

Ken Gibala

=====================

RE: Re: efficacy of germicidal UV

Just a note of caution from experience - U.V. lamps installed in such a manner as to expose media filters to the light will cause a rapid disintegration of the filter material. Curtis Redington, RSEnvironmental Quality SpecialistCity of Wichita Dept. of Environmental HealthWichita, KS-----Original Message-----From: iequality [mailto:iequality ]OnBehalf Of Jeff MaySent: Friday, April 07, 2006 6:54 PMTo: iequality Subject: Re: efficacy of germicidal UV, I posted this when the study came out: In a recent paper, "Effect of ultraviolet germicidal lights in office ventilation systems on workers' health and well-being: double-blind multiple crossover trial," (Lancet 2003; 362: 1785-91), the authors Menzies et.al. concluded that "installation of UVGI in most North American offices could resolve work-related symptoms in about 4 million employees, caused by microbial contamination of the heating, ventilation and air-conditioning systems." Despite the fact that ultraviolet germicidal irradiation (UVGI) has been shown in many previous studies to reduce airborne contagion, I believe that the conclusion of this study overstates the impact of UVGI on HVAC systems and office indoor air quality. Three healthy, well-ventilated (peak values of carbon dioxide were under 620 ppm) office buildings in Montreal, Canada were evaluated over the course of one year (July 1999 to July 2000). In the study, UV lamps (245-266 nm wavelength band), rated at 450 mW/cm2 at a distance of one meter, were mounted with reflectors 15 to 74 cm from the cooling coils and drip pans. At this level of irradiation (greater than what is typical), the authors estimated that the survival time for resistant organisms would be less than 4 minutes. Within the HVAC system, the UVGI lamps were cycled, operating for 12 weeks off, and then 4 consecutive weeks on. Questionnaires were repeatedly distributed to about 800 office workers to obtain subjective opinions regarding environmental satisfaction and allergy symptoms (categories included systemic, mucosal, respiratory, musculo-skeletal, and "any symptom") during the different time intervals. The concentration of microbes on the coils and in the drip pans was determined by placing sterile 5 cm x 5 cm "coupons" of sheet metal on the surfaces (exposed directly to the UVGI), and then placing the exposed coupons on a Petri dish containing culture media (Sabouraud or MEA), and incubating the dishes. Coupons (receiving no UVGI) were also placed on the filters. Air samples indoors and outdoors were obtained with Burkard volumetric air samplers (with Petri dishes) to determine the concentration of fungal spores. A total of 1240 samples were assayed. Endotoxin concentrations were determined using volumetric sampling and polycarbonate filter cassettes for the air, and by washings directly from the dust impacted on the coupon surfaces. A total of 284 samples were assayed. Airborne endotoxin was not detectable at workstations with the UVGI either on or off and there was a slight increase in levels on the filter coupons with the UVGI on. The amount of endotoxin on the coil coupon dropped from 8 endotoxin units (EU) to zero with the UVGI on. Culturable air samples for fungal spores at both the returns and supplies, with the UVGI both on and off, were 0 (zero) cfu/m3. The number of culturable spores per 25 cm2 on all coupons was very low, and averaged at the cooling coil from 0 (UVGI on) to about 4 (UVGI off) or far less than one spore per cm2 after a 4- or 12-week exposure period. The coupons on the filters collected 3 cfu/coupon (UVGI off) and 2 cfu/coupon (UVGI on). The coupons may not have been very efficient collectors since they lacked a "sticky" coating and were positioned perpendicular to the air flows and thus obstructed the stream lines. In addition, the irradiated coupons were exposed directly to the UVGI, whereas microbes on an actual HVAC surface would have received incident light at a variety of angles, the intensity of which would be attenuated by the dust accumulations. The data and results for different seasons were not separated. Since in Montreal there is a long heating season and a short cooling season, the expected results for each season should be quite different. In addition, during the heating season there is no condensation of moisture to promote microbial growth. In fact, in the presence of minimal dust on the coupons and few organisms, and without moisture, there is little opportunity for any microbial amplification, either in the heating or cooling season. Despite the reported reduction in symptoms indoors at work during the UVGI-on periods, no statistically significant differences were reported in the indoor air concentrations of microbes at work stations; thus the authors were left with no explanation for the reported reduction in symptoms associated with UVGI. (The authors postulated that the UVGI radiation may have somehow reduced the aerosolization of microbial antigenic proteins.) To prevent microbial growth due to moisture or high relative humidity in HVAC systems, the most important components of hygiene will always be proper design to begin with, adequate filtration (a minimum of MERV 6-8), and regular maintenance. Though UVGI may certainly serve as an adjunct in disinfecting exposed air and reducing microbial growth on irradiated surfaces, the impact on overall indoor air quality of UVGI alone should not be overstated. C. MayMay Indoor Air Investigations LLC1522 Cambridge StreetCambridge, MA 02139www.mayindoorair.comwww.myhouseiskillingme.com

[Guest guest]

Curtis:

OSHA requires that all commercial HVAC systems to be inspected and serviced

at least annually, and changing filters does not constitute: " inspection and

service. " Residential HVAC systems do not have any requirements. Moreover,

UV lamps do not necessarily need to be changed annually; it is entirely

dependent upon hours of use, and better quality bulbs have a longer lamp

life than the cheap ones. (Similarly with tungsten light bulbs.) Also,

properly cleaning HVAC systems can cost thousands of $$$, depending upon the

size of the system. A good cleaning often exceeds the cost of a UV

installation, and I have seen where system cleaning combined with improved

filtration and UV irradiation has paid for itself in as little as four years

due to reduced maintenance, cleaning, and energy costs. It is definitely a

trade off. I don't consider UV irradiation to be any more of a " special

treatment system " than I do a MERV-11 filter bank. And your point " few

people will spend the money for the annual service, unless they have a

sizable chunk of money tied up in some special treatment system " is very

well said. Moreover, many building owners feel that if they install a

high-end mechanical control, it is a walk-away system; which is often not

the case. Residential owners consistently fail to pay attention or spend

money on their HVAC system until is causes illness or harm; when a bit of

periodic maintenance and money spent would have prevented the problem from

becoming a monster. I think your idea of annual inspections, cleaning and

maintenance is a good point, but few building owners do it, and in some

situations, annual cleaning may not be sufficient. However, it would be a

good start.

--

Geyer, PE, CIH, CSP

President

KENTEC Industries, Inc.

Bakersfield, California

www.kerntecindustries.com

> Given the initial installation cost for U.V., plus the annual lamp replacement

> cost, wouldn't it be cheaper but just as effective to simply have your HVAC

> inspected, cleaned, and otherwise serviced each year? Only it seems very few

> people will spend the money for the annual service, unless they have a sizable

> chunk of money tied up in some " special treatment system " .

>

> Curtis Redington, RS

> Environmental Quality Specialist

> City of Wichita Dept. of Environmental Health

> Wichita, KS

>

> Re: efficacy of germicidal UV

>

>

> Mike,

>

> I am not arguing that UV isn't germicidal, but without a clean system to

> begin with, and efficient filtration (minimum MERV 6-8, preferably MERV 11)

> in place to keep the linings and coil clean, UV is worthless.

>

> And few installers take the care that you seem to; based on the

> installations I've seen, most just pop a lamp in someplace and walk off with

> the exorbitant fee.

>

> For the money, I'd spend on cleaning and filtration before UV irradiation.

>

> C. May

> May Indoor Air Investigations LLC

> 1522 Cambridge Street

> Cambridge, MA 02139

>

> www.mayindoorair.com

> www.myhouseiskillingme.com

>

>

> Geyer writes:

>

>> :

>>

>> I, for one, believe the science behind UV irradiation as a germicidal method

>> is very sound. I have seen (by my measurements) a tremendous reduction in

>> active colony forming units inside HVAC systems (e.g., duct work, heat

>> exchangers, fan blades, etc.) when UV lamps are installed. There was one

>> negative comment recently about " UV killing spores whizzing by. " I for one

>> believe it does work, although, like any engineering control, there are

>> limitations. If the air speed (velocity) is really high and the UV lamp

>> energy is low, there is a significant reduction in effect. If poorly

>> designed/installed, the benefits of UV irradiation can be negligible. The

>> lamps I have installed in HVAC systems are REALLY strong and warrant LOTO

>> controls so they are not energized when the HVAC system is worked on, or if

>> filters are changed. Moreover, they are shielded on the upstream side so

>> debris/particulates do not impact and soil the bulbs. I usually place the

>> lamps 4 to 6 inches from the heat exchanger (HE) on the upwind side, and

>> rarely am I installing less than three lamps. I don't like placing them in

>> dirty HVAC systems and when I install them on a retrofit, it is after the

>> system is thoroughly cleaned. In side by side comparisons, i.e., HEs with

>> lamps versus HEs without lamps, the cleanliness of the HEs with lamps could

>> be easily seen one year later. In fact, the HEs (with lamps) looked as

>> clean as the day the lamps were installed, while the other HEs had visible

>> dirt on them. There is a lot to designing and installing UV systems in HVAC

>> systems to make them effective - it is NOT a plug-n-play control. I know

>> Kaiser Permanente has invested heavily in UV irradiation of their HVAC

>> systems in an effort to control infection. I believe their results are

>> really supportive of UV irradiation. A big advantage of UV irradiation is

>> the low cost to operate. A big disadvantage is the high cost of each (good

>> quality) bulb, and several bulbs are needed in each fan unit on small

>> package units. On buildings with a centralized HVAC system (versus

>> individual roof-mounted package units) there could be 20 to 30 bulbs, or

>> more. Moreover, the HVAC fan unit must be so located that is can be easily

>> serviced (not a problem with centralized HVAC systems). This is not the

>> case in most residential construction because most architects/contractors

>> design and place the fan unit in the attic...a very convenient but really

>> dumb place to put a piece of machinery that needs periodic service with

>> filters that warrant frequent replacing.

>>

>> If I had a house that had central air (I don't, we open windows) I would

>> install UV irradiation along with an appropriate, well-sealed, HPFF filter

>> bank; and it would deliver the cleanest air at the best, and lowest,

>> operating cost. I am a believer in UV.

>>

>> For what it is worth...

>> --

>> Geyer, PE, CIH, CSP

>> President

>> KENTEC Industries, Inc.

>> Bakersfield, California

>> www.kerntecindustries.com

>>

>>

>>

>>

>>

>>

>>

>>> Hi all,

>>>

>>> Not too long ago, AirwaysEnv@... wrote:

>>>

>>>> Unfortunately, science and scientists do not exist outside of

>>>> economics and finance. It can be seen in the way new technologies

>>>> are marketed today that the line between science and marketing gets

>>>> fuzzier and fuzzier. How about all these pharmaceutical

>>>> advertisements on television today? Or ozone generating air

>>>> purifiers. Or the science behind UV light bulbs in ducts to kill

>>>> mold spores whizzing by...

>>>

>>> I thought that the science behind germicidal UV was sound. Anyone have

>>> any thoughts on the matter?

>>>

>>> Thanks,

>>>

>

>

>

>

>

>

>

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[Guest guest]

It is the intensity of the

UV that kills the bacteria and mold. I don't

recall the exact numbers but UV biosafety hood lights are about 100 or

more times more intense than sun light.

Bob, I have to make a slight correction here. The dose is the

poison. Intensity is just part of that equation. For UV, dose

= intensity + exposure time with the correct wavelength for the

biologicals of interest. For a kill, biologicals on surfaces can be

exposed to lower intensity light because they can be exposed for a much

longer time than those floating through the light in an air stream.

The latter require much more intense light because exposure time is so

short. Note that I know I am presenting the simplistic

picture. Other factors, such as moisture and dust concentrations

can impact exposure.

******************************************************

If what is written looks too stupid to be written by me, I disclaim

it. On

the other hand, if it is brilliant, then I have no one to blame but

myself.

Otherwise, whether you choose to accept my opinion is up to you.

******************************************************

K. Klein, PE ME, MBA

Indoor Air Quality Solutions, Inc.

2523 SR 133

Bethel, OH 45106-0007

VOICE:

FAX: (with notice)

E-mail: mkklein68@...

*******************************************************

Wouldn't it be nice if common sense were really common?

[Guest guest]

Jeff,

Thank you for referencing the 2003 presentation from Lancet. It is revealing in several ways.

I'm tending to agree with you when you say: "conclusion of this study overstates the impact of UVGI on HVAC systems and office indoor air quality". You seem to question the value of UV to measurably improve airborne microbial contamination of work or living spaces in occupied buildings while Geyer in his rebuttal praises UV from years of experience as a professional engineer in the building maintenance field.

I have been following this discussion with intense interest and wonder of each of you are correct but looking at different aspects of the UV science and thusly not following each other.

Geyer seems to be praising well engineered UV installations as a justifiable means of reducing the maintenance costs of large air handling installations. UV in those installations can measurably show that coils, chillers and other aspects of the mechanical system can be kept free of fungus and other microbial growth thus require less power to operate and maintain a high efficiency of cooling.

On the other hand those of us primarily interested in the air quality of inhabitable spaces question whether such UV can bring contamination to acceptable levels.

When I read; "the authors estimated that the survival time for resistant organisms would be less than 4 minutes" I immediately ask myself if that means that to be fatal microbes must receive radiation for up to four minutes. If this is the case then possibly there is little reason to expect improvements of bacterial levels of habitable spaces. These UV installations are designed specifically to keep clean the coils and other parts of the HVAC system susceptible to becoming clogged with fungal growth.

On the other hand newer UV installations designed with a catalytic target utilize the radiation principally to generate a fume of hydro peroxide radicals able to reduce microbial contamination by a log factor of 2.5-3.0. Testing has been done against samples of many of the microbials causing severe nosocomial infections and all seem to succumb to the products of the system. It is however noted that installation of these systems are recommended after the air handler not before.

Might we have a discussion.

Gibala

Re: efficacy of germicidal UV

, I posted this when the study came out: In a recent paper, “Effect of ultraviolet germicidal lights in office ventilation systems on workers’ health and well-being: double-blind multiple crossover trial,” (Lancet 2003; 362: 1785-91), the authors Menzies et.al. concluded that “installation of UVGI in most North American offices could resolve work-related symptoms in about 4 million employees, caused by microbial contamination of the heating, ventilation and air-conditioning systems.” Despite the fact that ultraviolet germicidal irradiation (UVGI) has been shown in many previous studies to reduce airborne contagion, I believe that the conclusion of this study overstates the impact of UVGI on HVAC systems and office indoor air quality. Three healthy, well-ventilated (peak values of carbon dioxide were under 620 ppm) office buildings in Montreal, Canada were evaluated over the course of one year (July 1999 to July 2000). In the study, UV lamps (245-266 nm wavelength band), rated at 450 mW/cm2 at a distance of one meter, were mounted with reflectors 15 to 74 cm from the cooling coils and drip pans. At this level of irradiation (greater than what is typical), the authors estimated that the survival time for resistant organisms would be less than 4 minutes. Within the HVAC system, the UVGI lamps were cycled, operating for 12 weeks off, and then 4 consecutive weeks on. Questionnaires were repeatedly distributed to about 800 office workers to obtain subjective opinions regarding environmental satisfaction and allergy symptoms (categories included systemic, mucosal, respiratory, musculo-skeletal, and “any symptom”) during the different time intervals. The concentration of microbes on the coils and in the drip pans was determined by placing sterile 5 cm x 5 cm “coupons” of sheet metal on the surfaces (exposed directly to the UVGI), and then placing the exposed coupons on a Petri dish containing culture media (Sabouraud or MEA), and incubating the dishes. Coupons (receiving no UVGI) were also placed on the filters. Air samples indoors and outdoors were obtained with Burkard volumetric air samplers (with Petri dishes) to determine the concentration of fungal spores. A total of 1240 samples were assayed. Endotoxin concentrations were determined using volumetric sampling and polycarbonate filter cassettes for the air, and by washings directly from the dust impacted on the coupon surfaces. A total of 284 samples were assayed. Airborne endotoxin was not detectable at workstations with the UVGI either on or off and there was a slight increase in levels on the filter coupons with the UVGI on. The amount of endotoxin on the coil coupon dropped from 8 endotoxin units (EU) to zero with the UVGI on. Culturable air samples for fungal spores at both the returns and supplies, with the UVGI both on and off, were 0 (zero) cfu/m3. The number of culturable spores per 25 cm2 on all coupons was very low, and averaged at the cooling coil from 0 (UVGI on) to about 4 (UVGI off) or far less than one spore per cm2 after a 4- or 12-week exposure period. The coupons on the filters collected 3 cfu/coupon (UVGI off) and 2 cfu/coupon (UVGI on). The coupons may not have been very efficient collectors since they lacked a “sticky” coating and were positioned perpendicular to the air flows and thus obstructed the stream lines. In addition, the irradiated coupons were exposed directly to the UVGI, whereas microbes on an actual HVAC surface would have received incident light at a variety of angles, the intensity of which would be attenuated by the dust accumulations. The data and results for different seasons were not separated. Since in Montreal there is a long heating season and a short cooling season, the expected results for each season should be quite different. In addition, during the heating season there is no condensation of moisture to promote microbial growth. In fact, in the presence of minimal dust on the coupons and few organisms, and without moisture, there is little opportunity for any microbial amplification, either in the heating or cooling season. Despite the reported reduction in symptoms indoors at work during the UVGI-on periods, no statistically significant differences were reported in the indoor air concentrations of microbes at work stations; thus the authors were left with no explanation for the reported reduction in symptoms associated with UVGI. (The authors postulated that the UVGI radiation may have somehow reduced the aerosolization of microbial antigenic proteins.) To prevent microbial growth due to moisture or high relative humidity in HVAC systems, the most important components of hygiene will always be proper design to begin with, adequate filtration (a minimum of MERV 6-8), and regular maintenance. Though UVGI may certainly serve as an adjunct in disinfecting exposed air and reducing microbial growth on irradiated surfaces, the impact on overall indoor air quality of UVGI alone should not be overstated. C. MayMay Indoor Air Investigations LLC1522 Cambridge StreetCambridge, MA 02139www.mayindoorair.comwww.myhouseiskillingme.com iamnotanairhead writes: > Hi all, > > Not too long ago, AirwaysEnv@... wrote: > >>Unfortunately, science and scientists do not exist outside of >> economics and finance. It can be seen in the way new technologies >>are marketed today that the line between science and marketing gets >> fuzzier and fuzzier. How about all these pharmaceutical >> advertisements on television today? Or ozone generating air >> purifiers. Or the science behind UV light bulbs in ducts to kill >>mold spores whizzing by...> > I thought that the science behind germicidal UV was sound. Anyone have > any thoughts on the matter? > > Thanks,>

[Guest guest]

Ken –

From what I can gather, the other major concern with

residentially installed units is them emitting ozone.

Someone please correct me if I’m wrong.

Stacey Champion

From: iequality [mailto:iequality ] On Behalf Of kengib .

Sent: Tuesday, April 11, 2006

10:24 AM

To: iequality

Subject: Re: Re:

efficacy of germicidal UV

Jeff,

Thank you

for referencing the 2003 presentation from Lancet. It is revealing

in several ways.

I'm tending to

agree with you when you say: " conclusion

of this study overstates the impact of UVGI on HVAC systems

and office indoor air quality " . You seem

to question the value of UV to measurably improve airborne microbial

contamination of work or living spaces in occupied buildings while

Geyer in his rebuttal praises UV from years of experience as a professional

engineer in the building maintenance field.

I have been

following this discussion with intense interest and wonder of each of you are

correct but looking at different aspects of the UV science and thusly not

following each other.

Geyer seems to

be praising well engineered UV installations as a justifiable means of

reducing the maintenance costs of large air handling

installations. UV in those installations can measurably show

that coils, chillers and other aspects of the mechanical system can be kept

free of fungus and other microbial growth thus require less power to operate

and maintain a high efficiency of cooling.

On the other

hand those of us primarily interested in the air quality of

inhabitable spaces question whether such UV can bring contamination

to acceptable levels.

When I read;

" the authors estimated that the

survival time for resistant organisms would be less than 4 minutes " I

immediately ask myself if that means that to be fatal microbes

must receive radiation for up to four minutes. If this is the case

then possibly there is little reason to expect improvements of

bacterial levels of habitable spaces. These UV installations are designed

specifically to keep clean the coils and other parts of the HVAC system

susceptible to becoming clogged with fungal growth.

On the other

hand newer UV installations designed with a catalytic target utilize

the radiation principally to generate a fume of hydro peroxide radicals

able to reduce microbial contamination by a log factor of 2.5-3.0.

Testing has been done against samples of many of the microbials

causing severe nosocomial infections and all seem to succumb to the

products of the system. It is however noted that installation of these

systems are recommended after the air handler not before.

Might we have a

discussion.

Gibala

Re: efficacy of germicidal UV

,

I posted this when the study came out:

In a recent paper, “Effect of ultraviolet

germicidal lights in office

ventilation systems on workers’ health and

well-being: double-blind multiple

crossover trial,” (Lancet 2003; 362:

1785-91), the authors Menzies et.al.

concluded that “installation of UVGI in most

North American offices could

resolve work-related symptoms in about 4 million

employees, caused by

microbial contamination of the heating,

ventilation and air-conditioning

systems.”

Despite the fact that ultraviolet germicidal

irradiation (UVGI) has been

shown in many previous studies to reduce airborne

contagion, I believe that

the conclusion of this study overstates the impact

of UVGI on HVAC systems

and office indoor air quality.

Three healthy, well-ventilated (peak values of

carbon dioxide were under 620

ppm) office buildings in Montreal, Canada

were evaluated over the course of

one year (July 1999 to July 2000). In

the study, UV lamps (245-266 nm

wavelength band), rated at 450 mW/cm2 at a

distance of one meter, were

mounted with reflectors 15 to 74 cm from the

cooling coils and drip pans. At

this level of irradiation (greater than what is

typical), the authors

estimated that the survival time for resistant

organisms would be less than

4 minutes. Within the HVAC system, the UVGI lamps

were cycled, operating for

12 weeks off, and then 4 consecutive weeks on.

Questionnaires were

repeatedly distributed to about 800 office workers

to obtain subjective

opinions regarding environmental satisfaction and

allergy symptoms

(categories included systemic, mucosal,

respiratory, musculo-skeletal, and

“any symptom”) during the different

time intervals.

The concentration of microbes on the coils and in

the drip pans was

determined by placing sterile 5 cm x 5 cm

“coupons” of sheet metal on the

surfaces (exposed directly to the UVGI), and then

placing the exposed

coupons on a Petri dish containing culture media

(Sabouraud or MEA), and

incubating the dishes. Coupons (receiving no UVGI)

were also placed on the

filters. Air samples indoors and outdoors were obtained

with Burkard

volumetric air samplers (with Petri dishes) to

determine the concentration

of fungal spores. A total of 1240 samples were

assayed.

Endotoxin concentrations were determined using

volumetric sampling and

polycarbonate filter cassettes for the air, and by

washings directly from

the dust impacted on the coupon surfaces. A total

of 284 samples were

assayed. Airborne endotoxin was not detectable at

workstations with the UVGI

either on or off and there was a slight increase

in levels on the filter

coupons with the UVGI on. The amount of endotoxin

on the coil coupon dropped

from 8 endotoxin units (EU) to zero with the

UVGI on.

Culturable air samples for fungal spores at both

the returns and supplies,

with the UVGI both on and off, were 0 (zero)

cfu/m3. The number of

culturable spores per 25 cm2 on all coupons was

very low, and averaged at

the cooling coil from 0 (UVGI on) to about 4 (UVGI

off) or far less than one

spore per cm2 after a 4- or 12-week exposure

period. The coupons on the

filters collected 3 cfu/coupon (UVGI off) and 2

cfu/coupon (UVGI on). The

coupons may not have been very efficient

collectors since they lacked a

“sticky” coating and were positioned

perpendicular to the air flows and thus

obstructed the stream lines. In addition, the

irradiated coupons were

exposed directly to the UVGI, whereas microbes on

an actual HVAC surface

would have received incident light at a variety of

angles, the intensity of

which would be attenuated by the dust

accumulations.

The data and results for different seasons were

not separated. Since in

Montreal there is a long heating season and a short cooling season,

the

expected results for each season should be quite

different. In addition,

during the heating season there is no condensation

of moisture to promote

microbial growth. In fact, in the presence of

minimal dust on the coupons

and few organisms, and without moisture, there is

little opportunity for any

microbial amplification, either in the heating or

cooling season.

Despite the reported reduction in symptoms indoors

at work during the

UVGI-on periods, no statistically significant

differences were reported in

the indoor air concentrations of microbes at work

stations; thus the authors

were left with no explanation for the reported

reduction in symptoms

associated with UVGI. (The authors postulated that

the UVGI radiation may

have somehow reduced the aerosolization of

microbial antigenic proteins.)

To prevent microbial growth due to moisture or

high relative humidity in

HVAC systems, the most important components of

hygiene will always be proper

design to begin with, adequate filtration (a

minimum of MERV 6-8), and

regular maintenance. Though UVGI may certainly

serve as an adjunct in

disinfecting exposed air and reducing microbial

growth on irradiated

surfaces, the impact on overall indoor air quality

of UVGI alone should not

be overstated.

C. May

May Indoor Air Investigations LLC

1522

Cambridge Street

Cambridge, MA 02139

www.mayindoorair.com

www.myhouseiskillingme.com

iamnotanairhead writes:

> Hi all,

>

> Not too long ago, AirwaysEnv@... wrote:

>

>>Unfortunately, science and scientists do

not exist outside of

>> economics and finance. It can be

seen in the way new technologies

>>are marketed today that the line between

science and marketing gets

>> fuzzier and fuzzier. How about all

these pharmaceutical

>> advertisements on television today?

Or ozone generating air

>> purifiers. Or the science behind UV

light bulbs in ducts to kill

>>mold spores whizzing by...

>

> I thought that the science behind germicidal

UV was sound. Anyone have

> any thoughts on the matter?

>

> Thanks,

>

[Guest guest]

Yes Stacey, I've heard that before but have no reason to believe it need be a problem. With the UVGI installations recently discussed here where a UV bulb is installed before the air handler it is doubtful any ozone could survive the turbulence of the fans. We should understand the physical and chemical nature of ozone. Let's review: Ozone is extremely fragile or unstable. It has a normal half life of less than 25 minutes. Thus overnight there should be virtually no natural ozone remaining in a residence unless windows are allowed to be open for ventilation. Any turbulence will reduce the half life to minutes. With UV bulbs there can be ozone produced at the wave length of UVA. I'm told there is little or no ozone produced at the wavelength of UVC; in fact, the recent Lancet article referenced by Jeff Mays showed that with the UV cycled on there was less measurable ozone in the room than when off indicating that UVC consumes [breaks down] ozone. To go one step further.......The principle of photohydroionization is to use a broad band bulb operating the range between 185 nm and 254 um and focused toward a target with an appropriate catalytic coating. At 185 nm ozone is produced and simultaneously consumed by uv at 254 nm. In the process with the rh above 10%, quantities of advanced oxygen compounds hydro peroxide and hydroxyl radicals are produced along with amounts of O5. These substances rapidly destroy the cell membranes of most microbials without presenting any known hazard to humans. Now please don't ask me why the advanced oxygen compounds are no hazard to humans. It'll take a good microbiologist to explain which I am not.. Ken Gibala Re: efficacy of germicidal UV , I posted this when the study came out: In a recent paper, “Effect of ultraviolet germicidal lights in office ventilation systems on workers’ health and well-being: double-blind multiple crossover trial,” (Lancet 2003; 362: 1785-91), the authors Menzies et.al. concluded that “installation of UVGI in most North American offices could resolve work-related symptoms in about 4 million employees, caused by microbial contamination of the heating, ventilation and air-conditioning systems.” Despite the fact that ultraviolet germicidal irradiation (UVGI) has been shown in many previous studies to reduce airborne contagion, I believe that the conclusion of this study overstates the impact of UVGI on HVAC systems and office indoor air quality. Three healthy, well-ventilated (peak values of carbon dioxide were under 620 ppm) office buildings in Montreal, Canada were evaluated over the course of one year (July 1999 to July 2000). In the study, UV lamps (245-266 nm wavelength band), rated at 450 mW/cm2 at a distance of one meter, were mounted with reflectors 15 to 74 cm from the cooling coils and drip pans. At this level of irradiation (greater than what is typical), the authors estimated that the survival time for resistant organisms would be less than 4 minutes. Within the HVAC system, the UVGI lamps were cycled, operating for 12 weeks off, and then 4 consecutive weeks on. Questionnaires were repeatedly distributed to about 800 office workers to obtain subjective opinions regarding environmental satisfaction and allergy symptoms (categories included systemic, mucosal, respiratory, musculo-skeletal, and “any symptom”) during the different time intervals. The concentration of microbes on the coils and in the drip pans was determined by placing sterile 5 cm x 5 cm “coupons” of sheet metal on the surfaces (exposed directly to the UVGI), and then placing the exposed coupons on a Petri dish containing culture media (Sabouraud or MEA), and incubating the dishes. Coupons (receiving no UVGI) were also placed on the filters. Air samples indoors and outdoors were obtained with Burkard volumetric air samplers (with Petri dishes) to determine the concentration of fungal spores. A total of 1240 samples were assayed. Endotoxin concentrations were determined using volumetric sampling and polycarbonate filter cassettes for the air, and by washings directly from the dust impacted on the coupon surfaces. A total of 284 samples were assayed. Airborne endotoxin was not detectable at workstations with the UVGI either on or off and there was a slight increase in levels on the filter coupons with the UVGI on. The amount of endotoxin on the coil coupon dropped from 8 endotoxin units (EU) to zero with the UVGI on. Culturable air samples for fungal spores at both the returns and supplies, with the UVGI both on and off, were 0 (zero) cfu/m3. The number of culturable spores per 25 cm2 on all coupons was very low, and averaged at the cooling coil from 0 (UVGI on) to about 4 (UVGI off) or far less than one spore per cm2 after a 4- or 12-week exposure period. The coupons on the filters collected 3 cfu/coupon (UVGI off) and 2 cfu/coupon (UVGI on). The coupons may not have been very efficient collectors since they lacked a “sticky” coating and were positioned perpendicular to the air flows and thus obstructed the stream lines. In addition, the irradiated coupons were exposed directly to the UVGI, whereas microbes on an actual HVAC surface would have received incident light at a variety of angles, the intensity of which would be attenuated by the dust accumulations. The data and results for different seasons were not separated. Since in Montreal there is a long heating season and a short cooling season, the expected results for each season should be quite different. In addition, during the heating season there is no condensation of moisture to promote microbial growth. In fact, in the presence of minimal dust on the coupons and few organisms, and without moisture, there is little opportunity for any microbial amplification, either in the heating or cooling season. Despite the reported reduction in symptoms indoors at work during the UVGI-on periods, no statistically significant differences were reported in the indoor air concentrations of microbes at work stations; thus the authors were left with no explanation for the reported reduction in symptoms associated with UVGI. (The authors postulated that the UVGI radiation may have somehow reduced the aerosolization of microbial antigenic proteins.) To prevent microbial growth due to moisture or high relative humidity in HVAC systems, the most important components of hygiene will always be proper design to begin with, adequate filtration (a minimum of MERV 6-8), and regular maintenance. Though UVGI may certainly serve as an adjunct in disinfecting exposed air and reducing microbial growth on irradiated surfaces, the impact on overall indoor air quality of UVGI alone should not be overstated. C. MayMay Indoor Air Investigations LLC1522 Cambridge StreetCambridge, MA 02139www.mayindoorair.comwww.myhouseiskillingme.com iamnotanairhead writes: > Hi all, > > Not too long ago, AirwaysEnv@... wrote: > >>Unfortunately, science and scientists do not exist outside of >> economics and finance. It can be seen in the way new technologies >>are marketed today that the line between science and marketing gets >> fuzzier and fuzzier. How about all these pharmaceutical >> advertisements on television today? Or ozone generating air >> purifiers. Or the science behind UV light bulbs in ducts to kill >>mold spores whizzing by...> > I thought that the science behind germicidal UV was sound. Anyone have > any thoughts on the matter? > > Thanks,>

[Guest guest]

,

What is the life span or half-life of the hydro peroxide

radicals and other components of this fume? Do they last long enough

to actually make it out of the air handler? the supply registers?

Ron

> >

> >>Unfortunately, science and scientists do not exist outside of

> >> economics and finance. It can be seen in the way new

technologies

> >>are marketed today that the line between science and marketing

gets

> >> fuzzier and fuzzier. How about all these pharmaceutical

> >> advertisements on television today? Or ozone generating air

> >> purifiers. Or the science behind UV light bulbs in ducts to

kill

> >>mold spores whizzing by...

> >

> > I thought that the science behind germicidal UV was sound.

Anyone have

> > any thoughts on the matter?

> >

> > Thanks,

> >

>

[Guest guest]

Ken,

Although I might not survive a pass through the HVAC blower, the ozone

definitely does. I have smelled it in the supply air of systems with dirty

electronic filters.

C. May

May Indoor Air Investigations LLC

1522 Cambridge Street

Cambridge, MA 02139

www.mayindoorair.com

www.myhouseiskillingme.com

kengib . writes:

> Yes Stacey,

>

> I've heard that before but have no reason to believe it need be a problem.

>

> With the UVGI installations recently discussed here where a UV bulb is

>installed before the air handler it is doubtful any ozone could survive >the

turbulence of the fans. We should understand the physical and chemical <snip>

[Guest guest]

Ron,

Ozone is an unstable compound because it is quite reactive, but it is

nonetheless a stable molecule in the sense that it exists as a gas. Although

there a few relatively complex free radical molecules that have been

" designed, " a small free radical has no more than a fraction of a second

existence (nanoseconds, femtoseconds, etc.) and is generally considered as

only an intermediate in a chemical reaction.

C. May

May Indoor Air Investigations LLC

1522 Cambridge Street

Cambridge, MA 02139

www.mayindoorair.com

www.myhouseiskillingme.com

ronmcirvin writes:

>

> ,

> What is the life span or half-life of the hydro peroxide

> radicals and other components of this fume? Do they last long enough

> to actually make it out of the air handler? the supply registers?

>

> Ron

>

[Guest guest]

Ron,

As I understand this, (after surviving a flame war about this in the

Building Biology group), the in-vivo half life of the hydroxyl radical is 10

to the -9 second. I would assume that would be similar in air, especially

turbulent air. It seems that the radical almost doesn't leave the catalyst

surface at all before it is done. Everyone feel free to correct me.

If this is so, we are fortunate since the hydroxyl radical is the king of

the radicals and can easily break DNA. Do we really need all this super

technology? What happened to building healthy buildings, good filtration

and proper air exchange (don't forget maintenance)?

Bruce

President

Bio-Home Solutions

Re: efficacy of germicidal UV

,

What is the life span or half-life of the hydro peroxide

radicals and other components of this fume? Do they last long enough

to actually make it out of the air handler? the supply registers?

Ron

> >

> >>Unfortunately, science and scientists do not exist outside of

> >> economics and finance. It can be seen in the way new

technologies

> >>are marketed today that the line between science and marketing

gets

> >> fuzzier and fuzzier. How about all these pharmaceutical

> >> advertisements on television today? Or ozone generating air

> >> purifiers. Or the science behind UV light bulbs in ducts to

kill

> >>mold spores whizzing by...

> >

> > I thought that the science behind germicidal UV was sound.

Anyone have

> > any thoughts on the matter?

> >

> > Thanks,

> >

>

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[Guest guest]

Bruce and Jeff,

If I understand correctly, you and Jeff (#6613) maintain that

of the " super oxidizers " produced by the photocatalytic process, only

the ozone (if any is produced by the UV lamps used as the energy

source for the photocatalyst) lasts long enough to leave the air

handler. Thus the statement " In just a few minutes you can install

state-of-the-art air purification technology into your HVAC

system . . . " which " . . . utilizes your HVAC fan to deliver safe

oxidizers and super-oxide ions throughout your home, . . . " has no

scientific basis for its claim.

Ron

> > >

> > >>Unfortunately, science and scientists do not exist outside of

> > >> economics and finance. It can be seen in the way new

> technologies

> > >>are marketed today that the line between science and

marketing

> gets

> > >> fuzzier and fuzzier. How about all these pharmaceutical

> > >> advertisements on television today? Or ozone generating air

> > >> purifiers. Or the science behind UV light bulbs in ducts to

> kill

> > >>mold spores whizzing by...

> > >

> > > I thought that the science behind germicidal UV was sound.

> Anyone have

> > > any thoughts on the matter?

> > >

> > > Thanks,

> > >

> >

>

>

>

>

>

>

>

>

>

>

> 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.

>

[Guest guest]

" O5 " ? what the heck is " O5 " ? how exactly does a molecule like that

form? what holds it together, even for a mini-micro-femtosecond?

how is it even possible? some pretty amazing electron sharing is

going on here. (maybe it was left behind when those UFOs landed.)

" advanced oxygen compounds " ? surely, this is a term created by a

marketing group.

O5.... hmmm, like in " Hawaii-O-5 " ? no wait a minute, that was 5-O.

(book 'em, Dan-o.)

for a good read on the FACTS about ozone, one of the best papers in

the literature remains: CJ Weschler (2000) " Ozone in Indoor

Environments: Concentration and Chemistry " , Indoor Air, 10:269-288.

from p. 270: " Ozone is a relatively stable molecule; only at high

ozone concentrations and/or elevated temperatures does it decompose

to oxygen at a significant rate. " and " Ozone is a very strong

oxidizing agent. Just a few species, such as fluorine, the

perxenate ion, atomic oxygen and the hydroxyl radical are more

powerful oxidants. However, this fact should not be misconstrued.

Although ozone is capable of oxidizing numerous gas phase species, a

large fraction of these ractions occur at a slow rate... "

read all about it.

Wane

<><><><><><><><><><><>

Wane A. Baker, P.E., CIH

Director, Air Quality Services

MICHAELS ENGINEERING INC.

" Real Professionals. 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

>

> With the UVGI installations recently discussed here where a UV

bulb is installed before the air handler it is doubtful any ozone

could survive the turbulence of the fans. We should understand the

physical and chemical nature of ozone. Let's review: Ozone is

extremely fragile or unstable. It has a normal half life of less

than 25 minutes. Thus overnight there should be virtually no

natural ozone remaining in a residence unless windows are allowed to

be open for ventilation. Any turbulence will reduce the half life to

minutes.

>

> With UV bulbs there can be ozone produced at the wave length of

UVA. I'm told there is little or no ozone produced at the

wavelength of UVC; in fact, the recent Lancet article referenced by

Jeff Mays showed that with the UV cycled on there was less

measurable ozone in the room than when off indicating that UVC

consumes [breaks down] ozone.

>

> To go one step further.......The principle of photohydroionization

is to use a broad band bulb operating the range between 185 nm and

254 um and focused toward a target with an appropriate catalytic

coating. At 185 nm ozone is produced and simultaneously consumed by

uv at 254 nm. In the process with the rh above 10%, quantities of

advanced oxygen compounds hydro peroxide and hydroxyl radicals are

produced along with amounts of O5. These substances rapidly destroy

the cell membranes of most microbials without presenting any known

hazard to humans.