Mold Air Testing

Hello all,

I am wondering where to get an air sample if it’s too cold or snowing?


Technically, you shouldn’t do air samples under those conditions.

I am aware of that. I am looking for an alternative for a control sample.

I am in Minnesota so it is an issue here as well. I have done them when it is above freezing with minimal snow cover. Below freezing can be troublesome.

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You cannot collect the outside sample & expect it to be accurate.
If anything, it could come back as a false positive for indoors.
<MG State Lic Mold Assessor #1573 :cowboy_hat_face:

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I understand that. I am asking if there is an alternative or should I just skip the test?

I have considered this scenario some myself. If the situation came up, I have wondered about offering to do the indoor samples with the disclaimer that I am not able to collect an outdoor baseline. If the indoor samples were highly elevated I would think there would be some value in the test. Heavy on the disclaimer portion though.

Nothing we can do about the prohibitive weather.
Some may consider collecting in the garage near an open door, not cool. Should be about 10 ft from structure & you can pick up mold from the garage.
I don’t see how any true value can be obtained only doing inside.
For example, penn/asp is quite common & can be more than 600 spores/m3 naturally inside. If there is no outside sample any assumption could be very inaccurate.
I’ve seen counts come back pretty high inside, but the basline control was much higher. You just do not know.
Good luck… … …

If you get an indoor spore count in excess of 5000 spores/m³ would it be considered problematic, even if you don’t have the outdoor sample(s) for control? I don’t know the answer. I’m curious if anyone knows.

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I’m not a mold guy, but wouldn’t it depend on the type of mold spores?

BUT, there is this:

Problems with indoor versus outdoor spore counts - comparing apples to oranges … A count of 200 Stachybotrys chartarum mold spores / M3 of air would be unusually high … What indoor mold spore level is considered “contaminated” then depends in part on what … Airborne Mold Spore Counts under 5,000 spores per m3.

This is my reference and the answer is yes.


I was thinking about this today because I just put out some mold inspection marketing. It is not recommended to perform baseline testing outdoors if there is snow cover. The reason being that the snow cover may “subdue” airborne mold spores that would otherwise be present, therefore giving you an inaccurate baseline. However, if there is a low airborne spore count outdoors due to snow cover, wouldn’t that also result in a low count indoors, all else being equal? Wouldn’t it be reasonable to conclude that sampling during below-freezing temps or active rain/snowfall may provide an inaccurate baseline, but snow cover by itself should not? This is of course assuming that the snow cover has been present long enough that the indoor air conditions have balanced.