Re: are air sample tests for mold pretty accurate?

November 28, 2008

If there is alot of mold in your house, almost any test will show it

up. If there is less but you are getting sick due to being exposed

for along period it can be harder to find out about. It could be

easy in first case, and in later case, it is really detective work.

If you are going to do just one test, I would do the dust test with

tape because it will pick up whatever has been deposited down there

no matter what the season or circumstances. I just got started using

plates and already now have a good idea of what is going on with my

house so I don't switch to tape method, and I also don't know where

to send them, but if you are just starting you might want to do tape

if someone here can tell you where to send it. Do it inside cold air

return though picking up from some place that has been undisturbed

for likely a long time. I have two cold air returns. I know this

will sound retarded but it is where air leaves house and goes down

into furnace system, not the areas where the heat or cool air comes

into the house...just in case you know as little as I did when I got

started.

The advantage of a petri dish is you can do one right away and since

you are worrying, you've got something started. You can pick them up

at Home Depot stores and put the petri dish on TOP of the cold air

return for however long it tells you to test with the fan 'on'. If

you have two cold air returns, do both of them. If they are in the

walls, you could tape them to grill with double sided tape or

something. If you do petri dish, make sure no windows are open

anywhere.

Petri dish will tell you something about what is going on 'now'.

Dust test will tell you 'something' about what has been going on over

a much longer period of time.

Regarding the plates: I have switched to using plates from Dallas

environmental center since I think they are more sensitive but that's

another story and the cost of them includes the testing up front and

you have to order them and wait to get them, etc, so for starters I

think the Home Depot plates are good for a beginning.

--- In , " TheBeth " <thebethinator@...>

wrote:

>

> So if I was to do an open petri air test, would it be pretty

accurate

> to at least find what kinds of mold are in the air if I set it in

> front of the return with the unit running?

November 28, 2008

Beth,

Viable sampling is different than spore trap sampling, and I think

that it typically reveals a different cross section of mold species. I

don't think that its possible to describe the differences or why they

happen in two or three paragraphs. There are a huge number of

variables.

There are spores everywhere in the air, most of them are not

toxinogenic species. There are also differences in media, (the kind of

agar used in the " petri dish " agar plates) and differences in tme

exposed to spore settling, time of day opened, wind conditions at that

time, temperature and length of time mold is allowed to grow before

analysis, etc, etc.

The problems with stachybotrys not shedding spres unless it is

stressed also apply to viable sampling for airborne species.

Its very distressing how little money people have for testing.

*The testing should be reasonably priced and a standardized package of

tests and a certain protocol followed that is made uniform for all

homes or all workplaces. There really should be a minimum number of

tests done as part of that package. I would say at least five

including at least two spore trap tests for a one story apartment and

the number of floors plus one (outdoors, at least 100 feet from the

residence, upwind) with the tests being done in occupied bedroom if

its not possible to test a variety of rooms. There should also be at

least one ERMI test done with an averaged dust sample drawn while

there is negative air pressure. I would say all the indoor tests

dhould be done using negative air pressure unless the negative air

pressure creates an absolutely intolerable condition in a CURRENTLY

INHABITED HOME.. (negative pressure should always be used in vacant

homes, because vacant homes by virtue of not being occupied, are in a

very atypical state.. )

Bulk or tape lift sampling should also be done of any visible mold,

even f there are many instances of visible mold, say in a basement..

(tape lifts are so cheap that it pays to do as many as is necessary.

and in my experience they can be all over the map in what they find..)

Testing for mold is complicated. Doing three or four tests is not

going to give you enough information to make any kind of important

decision in and of itself..

OTOH, if you already know there is a problem, and you are gradually

changing things trying to eradicate it, those isolated tests can each

give you another snapshot of a spot in space at an instant in time

that when put together with the other tests that have been done,

gradually paints of picture of a fungi situation in a home. When that

is superimposed over the other factors that effect IAQ, a picture

emerges..

When you have all that information together, it gets clearer and

clearer what is going on and whether efforts are progressing, the

final determnant of whether a building is safe or dangerous should be

the people in it - whether they are being made sick, not a few tests

done on calm wet mornings (less mold) or gusty dry afternoons (the

most respirable fragments) or windy days a few days after a rain..(the

most airborne outdoor spores, which can cover up even a very bad

indoor situation if spore counts are the criteria counted..)

Also, the more debris, the harder it is to count anything..

Its a battleground out there..

Also, most garden variety " mold inspectors " have just three day or so

" training " and they get most of their business from real estate

agents who would be reluctant to send them business if they failed

houses..

*something to keep in mind..*

Also, the sneakiness of stachybotrys and the persistance of

stachybotrys toxins in a building long after mold spores are dust

should be a sobering aspect of this to the mold sensitive...

November 29, 2008

LiveSimply,

Although negative pressure may bring in spores from wall and/or

ceiling cavities (and a basement or crawl space), I don't think that

this is the correct procedure for mold testing because it may give

unrealistic results. The goal of indoor testing should be determining

what is a typical exposure, and if the house is not normally

negatively pressurized, the test results would be atypical.

In addition, the results from negatively pressurizing a space may

confuse conditions, making it appear as though there is a problem with

the room air whereas the problem is elsewhere.

The indoor air should be tested under " normal " conditions. If there

are concerns about ceiling or wall cavities, these should be tested

separately. This way, the source of the problem can be found.

I usually test room air after gently waving a notebook, to simulate

modest ( " normal " ) room activity. If I believe that there is a problem

with the quiescent room air, I take a sampe of the undisturbed room

air first.

Unfortunately, air sampling rarely tells you about the source, so this

testing must be combined with a careful visual inspection and surface

and/or dust sampling.

With ducted systems, if air sampling is done, the air should be tested

first with the system off for at least an hour, then tested again

(preferably close to supply) after the system has been operating.

To put the difference between viable (culturable) and non-viable

(total) spore testing into perspective, I am participating in a study

of Apsergillus mold on furniture that has been stored in basements

(but ends up in living rooms!). The highly-friable, moldy dust

(millions of spores per square inch) from the furniture is very

allergenic (to me!) but so far, only about one in 100,000 spores is

alive.

So exposures to mold spores can be very high but undetected by

culturable methods.

May

May Indoor Air Investigations LLC

Tyngsborough, MA