Re: PRV under negative air pressure

[Guest guest]

,

Things are not really "either or". I like to shut down the negative air (and/or scrubber) for about 10 minutes to let the air currents "homogenize" before taking an air sample. I do not like the idea of shutting off the negative air for longer periods until I have a good idea about how much contamination remains in the work area. I also like to spin the machine to disturb and aerosolize settled spores so that the air sample is representative of surface contamination. A leaf blower can be a good tool.

Bob and Gail s have done some good experimental research work to help answer some of these questions regarding PRV sampling.

Steve Temes

Thought I would try to pool some opinions on this. When performing

post remediation verification assessments for remediation of mold /

bacteria, one school of thought, it seems, is that AFDs should have

been shut down, some for as long as 24 hours, prior to any needed IAQ

testing. The other seems to be to perform IAQ testing while under

negative pressure to avoid any cross contamination.

I would like to know some of your thoughts on this. I have always

performed PRV assessments as my mentor taught me, but as we learn we

should evolve our methodology as well.

[Guest guest]

Hi, :

For PRV, I have performed the inspection of the site, requested a

lockdown sealant to be applied, and then vented for 48 hours prior to

conducting any post-remediation air sampling. I then turned off the

negative pressure during the sampling. My thought was that the

sampling should be done with the interference of the negative pressure.

I also would be interested in hearing what others are doing as well.

Don

>

> Thought I would try to pool some opinions on this. When performing

> post remediation verification assessments for remediation of mold /

> bacteria, one school of thought, it seems, is that AFDs should have

> been shut down, some for as long as 24 hours, prior to any needed IAQ

> testing. The other seems to be to perform IAQ testing while under

> negative pressure to avoid any cross contamination.

>

> I would like to know some of your thoughts on this. I have always

> performed PRV assessments as my mentor taught me, but as we learn we

> should evolve our methodology as well.

>

>

>

[Guest guest]

:

Let me preface my response with....what I typically do when conducting a PRV assessment; because there are times where the situation warrants something other than the typical.

Typically, I conduct a visual inspection and I often use a white glove (disposable cotton inspection glove). The glove is especially helpful in low-light containments where the only light is my flashlight. If the glove is excessively dirty, more cleaning is necessary. During the visual exam, I may or may not collect surface/micro-vac samples. It depends, e.g., What is the budget? What are the circumstances? What is the re-use? After passing the visual exam, I allow the remediation contractor to spray a lock-down encapsulant – but not all projects warrant an encapsulant. However, the more porous a substrate, the more an encapsulant is of value. I also like using encapsulants with a pigment when I can get away with it. Negative air machines are turned off during the encapsulation process, then after encapsulating I require new pre-filters installed on the neg-air machines. I like to see 12 to 24-hrs of air scrubbing, sometimes more, take place post-encapsulation. When I come to collect final clearance samples (if clearance samples are warranted), I often use the neg-air machines to blow air in several areas/directions (i.e., moved/spin them around), and I, more often than not, collect my air samples while the neg-air machines are operating and the air currents are aggressive. Moreover, I almost always collect several air samples near in front of the inlet to the neg-air machines - my thinking is: stuff is coming in this general direction, why not capture it. If I collect any surface samples, it is before encapsulating and not after encapsulating. Air samples are collected at any moment in the project......except when there is encapsulant condensate in the air.

For what it is worth.....

Thought I would try to pool some opinions on this. When performing

post remediation verification assessments for remediation of mold /

bacteria, one school of thought, it seems, is that AFDs should have

been shut down, some for as long as 24 hours, prior to any needed IAQ

testing. The other seems to be to perform IAQ testing while under

negative pressure to avoid any cross contamination.

I would like to know some of your thoughts on this. I have always

performed PRV assessments as my mentor taught me, but as we learn we

should evolve our methodology as well.

[Guest guest]

Don,,

Due to time I am unable to address this

issue although. Please allow me to take this up again after Feb 12, 2008.

Please someone address the sealant as a membrane which changes the permeability

of the materials and thus building design.

EnviroBob

From: iequality [mailto:iequality ] On Behalf Of Weekes

Sent: Wednesday, January 30, 2008

11:16 AM

To: iequality

Subject: Re: PRV under

negative air pressure

Hi, :

For PRV, I have performed the inspection of the site, requested a

lockdown sealant to be applied, and then vented for 48 hours prior to

conducting any post-remediation air sampling. I then turned off the

negative pressure during the sampling. My thought was that the

sampling should be done with the interference of the negative pressure.

I also would be interested in hearing what others are doing as well.

Don

>

> Thought I would try to pool some opinions on this. When performing

> post remediation verification assessments for remediation of mold /

> bacteria, one school of thought, it seems, is that AFDs should have

> been shut down, some for as long as 24 hours, prior to any needed IAQ

> testing. The other seems to be to perform IAQ testing while under

> negative pressure to avoid any cross contamination.

>

> I would like to know some of your thoughts on this. I have always

> performed PRV assessments as my mentor taught me, but as we learn we

> should evolve our methodology as well.

>

>

>

[Guest guest]

It depends on what you are trying to prove.

For a hospital, we will first sample with the NAMs on to be sure there

are not going to be spores migrating to occupied areas after the

containment is taken down.

Then testing can be done with the containment down and normal air

movement to determine if the area is suitable for reoccupancy.

The first step can often be eliminated if immunocompromised or highly

allergic occupants are not an issue.

Gail s