Why does one training program say to collect at a minimum 1 exterior air sample and 2 interior air samples and the other say 2 exterior and 1 interior? Which is the correct way?

William, I believe that the minimum you should collect for the exterior is one(1). This is used as the base. How many you collect on the interior is dependent on the circumstances, for instance if you need a swab sample or maybe different areas or mold distinctions.


The coarse that NACHI does says to take 2 exterior where as the coarse I took and the advanced coarse says to take 1 exterior. I am wondering which is the correct one?

I understand but, the course I took was with ESA and it was one (1) exterior. There is no need that I can think of to take any more than one (1) exterior base sample. That is my understanding.


Look who wrote the course and sponsored it and I am sure you can figure out why 2 exterior samples are required. I have taken 3 other mold certification courses by different associations and educators and they all recommend 1 outdoor sample. I have asked my lab (Not Pro-Lab mind you) and they recommend 1 outdoor sample as a control.

Instead, had you spent your time and energy taking 3 different mold tests outside 3 different sides of your home, only to discover how different the results are, you wouldn’t be asking who is right. You would have discovered that IAC2’s SOP is right and the other 3 associations and educators are wrong.

Pointing out that the laboratories make more money when you perform your mold inspection properly is like pointing out that home inspectors make more money when they sell mold inspections. What is your point?

You need to take at least 2 outdoor samples, especially if it is windy. Most of the time the results will be very similar, but enough of the time they will be so different as to warrant taking 2 all the time.

Right - Wrong?

Inspector should decide on number of outdoor samples. One before the inspection and one after the inspection is common; up wind and down wind etc. The decision is the inspectors regardless. Where home inspectors take their outdoor / indoor samples seems to be more of a problem than how many, at least here in Southwest Florida. Never cleaning their equipment between jobs is common among the dozen or so home inspectors I observe on a regular basis. Worrying about the number of samples seems pointless in too many HI mold inspections.

Just my view

I agree with Doug. In my experience, one up wind and one down wind reveals the greatest difference in outdoor samples.

And, what does this mean, exactly? How does one then determine the true spore count, and apply that to measurements gleaned from indoor samples? Herein lies the problem, making an already subjective “science” even more subjective, as you have now introduced yet another variable into the mix.

The NY City protocol for mold and mold remediation is the one most referred to by cities and government agencies, including Ontario.

I work with the CIH who wrote these standards.

He sits in the adjacent office.

His opinion would differ than those offered by both Nick and Doug Wall.

IAC2’s protocol runs contrary to all others.

That is your big scientific argument for doing it incorrectly?

I think IAC2 will continue to “run contrary” to doing it incorrectly. You’ll never convince me that “less data” is better than “more data” and I don’t care who you sit next to.

2 is not enough. I would recommend 10 exterior including different altitudes such as roof and basement stairwells. Those may not be sufficient so I will have to come back and do 5 more tomorrow.

My sales rep Mike, from Reliable Lab Inc told me so!:wink:

Cincinnati Ohio Mold Testing & Inspections

10 is too many and a waste of your client’s money. 1 is too few. 2 is correct.

This from the International Standards of Practice for Inspecting Commercial Properties, section 4.3:

It is one of the most important sentences in the inspection industry. Maybe the most important.

An outdoor sample should not be taken in/down the wind, period. Just get out of the wind when you test. The calmer the air the better.
Also you should follow the recommendations on what your Industrial Hygienist says. He is the one responsible for analyzing the samples correctly and you are responsible to follow this lead. He/she will not back you up when needed, if you do not listen to him/her. Let the IH decide what standard to use but make sure you know that standard well just in case you are asked. Carry a copy of it with you when you test.