Visually clean [was Interstitial Sampling, aka. The Wall Cavity Air Sample.]

[Guest guest]

One of my clients called me today for some questions for wall cavity samplig results, and I mentioned to her that although the surface of wall cavity appeared to be clean. There still can be significant amount of mold spores on the surface from (1) settled mold spores from air flow going through wall cavity (2) minimal mold growth (not dense) due to elevated moisture (no water damage). And, that's why her wall cavity samples have high number of spores.

The detection limits for visual inspection can be somewhere between 10,000 to 100,000 mold spore/in2 (or even higher) depending on spore color. Mold spores are microscopic. You can fit millions of spores in one tiny spot. That's visable. If you spread them out to 10 - 100 in2, they won't be visable to human eyes. Therefore, the detection limits for visual inspection can be somewhere between 10,000 to 100,000 spore/in2, or even higher. Be very careful when you say "it's clean" if visual inspection is all the information you have.

Wei

Sincerely, Wei Tang, Ph.D.

QLab Laboratory Director

QLab - Grow Your Business With Our Premium Analysis

5 DriveCherry Hill, NJ 08003Tel/Fax: 888-QLab-Wei ()Local:

www.QLabUSA.com

This message is intended only for the use of the individual or entity to which it is addressed, and may contain information that is privileged, confidential and exempt from disclosure under applicable law. If the reader of this message is not the intended recipient, or the employee or agent responsible for delivering the message to the intended recipient, you are hereby notified that any dissemination or copying of this communication is strictly prohibited. If you are not the intended reader and have received this communication in error, please notify us immediately by telephone.

To: iaqa-listserv@...; iequality Sent: Thu, December 30, 2010 12:15:26 AMSubject: Re: [iAQA-Listserv] Interstitial Sampling, aka. The Wall Cavity Air Sample.

No conclusion of IEQ investigation should be based on laboratory results alone. It should include building assessments (may include sampling), occupant interviews, building history review, etc. I am sure you all know this already. It's those people who are not here that we should worry about. Well, if their goal is to make money on the remediation jobs instead of improve occupant health, then it would not matter if they know this or not.

Wall cavity sampling can be useful if used correctly. Usually, reference sample(s) are recommended to form a "baseline" for a particular building location. If the sampling results of concerned area are significantly higher than that of the reference sample, then further investigation (e.g. opening a small panel of the wall cavity) need to be conducted to confirm that. Why not do that in the beginning? Small holes are much easier to patch up.

If the "baseline" results in reference samples for a particular building is high and you are certain that there is no water damage history in those areas, they might be the "normal fungal ecology" in those specific buildings types/ages/ locations. Do we need to remove that? Conduct air sampling in occupied space to see if they show up and go from there.

Why you need confirmation? Wall cavity "AIR" sampling is the sampling method for easily aerosolized "SURFACE" fungal biomass inside wall cavity. If you drill a hole right next to one single colony of mold, you hit a hot spot and you can easily collect millions of spores in the samples. If the rest of the surface is relatively clean, then the result is false positive.

Some fungal spores are not easily aerosolized. If you didn't pound the wall gently to loose and aerosolize, you may not collect those spores if the hole is too far away from mold growth, especially if there are insulation materials and/or barrier inside wall cavity to block air flows. Then, you may have false negative results.

Here is a more common cause for false negative results. If you drill the wall all the way through and push fine gypsum dust into the wall cavity, you will collect those dust in impaction-type spore traps and overload the sticky surface. It can produce significantly underestimated results because (1) the collection efficiency is reduced significantly because the sticky surface of impaction-type spore traps is overloaded with dust and cannot collect spores (2) the analysis accuracy is greatly affected because spores are buried within or loaded on the top of gypsum dust, which make it very difficult to see the spores.

Here is a solution:

MoldSense Wall Cavity Air Sampling Protocol

Author: Wei Tang

(a) Draw a line (or stick a piece of Scotch tape) on the drill bit 0.5 inch from the tip.

( In a desired and safe location far away from electrical wire, plumbing pipe, and

gas pipe, gently drill a hole on the dry wall up to the line on the drill bit without

penetrating the dry wall.

© Use a wet paper tower to wet the gypsum dust. Be careful not to let

the water affects any moisture reading in the building.

(d) Push through (not drill through) the hole to break the paper using clean object. Be careful not to touch or

damage any electrical wire, plumbing pipe, or gas pipe.

(e) Most commercial kit, spore trap, and pump can be used together after this point to

collect samples.

(f) Clean all tools thoroughly afterward to prevent cross-contamination.

Sincerely, Wei Tang, Ph.D.

QLab Laboratory Director

QLab - Grow Your Business With Our Premium Analysis

5 DriveCherry Hill, NJ 08003Tel/Fax: 888-QLab-Wei ()Local:

www.QLabUSA.com

This message is intended only for the use of the individual or entity to which it is addressed, and may contain information that is privileged, confidential and exempt from disclosure under applicable law. If the reader of this message is not the intended recipient, or the employee or agent responsible for delivering the message to the intended recipient, you are hereby notified that any dissemination or copying of this communication is strictly prohibited. If you are not the intended reader and have received this communication in error, please notify us immediately by telephone.

To: iaqa-listserv@...Sent: Wed, December 29, 2010 12:22:40 PMSubject: [iAQA-Listserv] Interstitial Sampling, aka. The Wall Cavity Air Sample.I have reviewed far too many reports that site an interstitial/wall cavitysample as the reason that a building or home requires extensive if notcomplete remediation. The cases brought to me have increase recently at analarming rate. Some of these samples have been collected on homes andbuildings on crawl spaces that were built as much as 75 years ago.All of the reports that I have reviewed included very little backgroundinformation and all had no elevated spore trap levels in the

living/occupiedspace. A few identified elevated moisture but none identified the cause andorigin of the moisture. All fell to the collection of air samples withinseveral walls for a period of 5 minutes at a rate of 15 liters to providethe clients with a smoking gun and an answer to what in their home or officewas making them sick.I believe the samples are collected in an attempt to justify the cost of theassessment by providing some form of a conclusion via laboratory results.If anyone out there is collecting wall cavity air sampling please help meunderstand how costly remediation can be based on these samples alone. Morespecifically why anyone would collect a wall sample from a 75 year oldbuilding on a crawl space with openings from the crawl space to the wallcavity. A lath and plaster wall cavity at that. Then recommend remediationand further

investigation.But then again I prefer to sample as little as possible during the initialinvestigation.Just venting a bit.P.S. My clients are the property owners and/or the property managementcompanies. The reports were all from tenant hired inspectors. P. Lapotaire, CIECBuilding Envelope & Indoor Environmental ConsultantFlorida State Licensed Mold Assessor MRS #4Microshield Environmental Services, LLCph fax <http://www.microshield-es.com/> www.Microshield-ES.com <http://www.linkedin.com/in/johnlapotaireciec> LinkedIn<http://www.iaqa.org/profile.asp?id=97> ACACBusiness Card----------------------------------------------------------------A blank message to these addresses performs the following

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