Mold testing: 1 or 2 outdoor control samples?

Hi y’all,
I just completed the training on mold testing and recall that 2 control samples were taken outside (1 windward and 1 leeward). I haven’t done any professional tests yet, but while researching what other companies do here in my local market of the Denver Metro area of Colorado, I see that some companies use a SOP of just 1 outdoor control. What am I missing, or are they doing it wrong?

Thanks in advance.

Nobody wants to answer this? let me get more specific. IAC2 guidelines state unequivocally that 3 air samples shall be taken (2 outside and one inside)

Axium Inspections who is IAC2 and InterNACHI accredited, states on their website that “We will have to take a minimum of two mold air samples: one mold test indoors and one mold test outdoors as a control.”

Mold Inspection & Testing, another company who operates in Denver and is also IAC2 certified, states on their website: Residential: $300-350 (Location Dependent) includes inspection, reports, and 2 Mold Tests (1 Control, 1 Inside)

I’m not trying to be a dumbass - this seems like a very basic question that has to have a definitive answer.

Are they just blowing QA out the window, or just undercutting everyone by offering less?
Thanks for anyone who can help me with this.

There are no “official” guidelines. So I guess you’re free to make up your own SOP.The EPA

IAC2 is about the only org that recommends 2 outside control samples. The most important decisions with the control sample are location and weather conditions that would render the sample useless. Maybe that is why they recommend two locations.

This is also a good read. They recommend 2 outside and 2 in each room of concern.

I think 3 samples at each location would be ideal (tie-breaker), but that would not be very cost effective for most clients. Keep in mind this article was written by the lab personnel (more lab fees). For preliminary mold screenings, I think one properly placed sample for each area of concern would be sufficient to show a problem.

Thanks so much for your thoughtful replies Frank and Bradley. Much appreciated.

I responded to the other thread

Doesn’t count. :slight_smile:

I would definitely do two outdoor and one indoor. It makes a huge difference when the test results come back and the samples are being compared to each other.