The ASHI Reporter Interviews Mold Expert Jeffrey C. May

The ASHI Reporter Interviews Mold Expert Jeffrey C. May

Mold spores are everywhere we live: homes, office buildings, schools, hotels. And today, homeowners are more aware than ever that mold is an issue to be addressed. For inspectors, this heightened awareness adds another dimension to each inspection and increases the need for education.

The ASHI Reporter recently spoke with Jeffrey C. May, mold expert and author of three books on mold and other indoor air quality (IAQ) issues. After 17 years as an ASHI inspector, May switched gears to become an IAQ professional and founded May Indoor Air Investigations LLC. He has investigated IAQ problems in thousands of structures, and he has a lot to say about mold.

Just how big is the mold issue?

“It’s really huge, enormous—I’ve been in over 1,000 sick buildings,” says May. While the ASHI Standards of Practice doesn’t cover IAQ issues, “inspectors need more trusted information, and they need to take the issue more seriously,” says May.

He sees a lot of denial in the industry, caused, he says, by insurance companies concerned that mold will become the next “asbestos,” leading to skyrocketing costs. But he argues that inspectors are on the front line and have the best chance of educating homeowners and improving the health of their homes—they owe it to their clients to address mold issues.

What are the main sources of mold?

“People get all bent out of shape from a patch of mold here or there, but the stuff that’s killing us is the stuff you usually can’t see, in the air conditioning system or carpets,” says May. In fact, whether you’re inspecting a residential or commercial property, he says, the air conditioning/heating system is most likely a source of mold contaminants.

Pull the cover off and look inside a blower cabinet, says May, and odds are good you’ll see as much as a half-inch of dirt and perhaps some stains. In those cases, there’s a “100 percent probability that there’s mold in there,” he says. “You can say, ‘use a better filter,’ but that’s not enough. A lot of times, the blower blades are covered with mold and spinning around,” he explains—continuously spraying mold spores into the air. “Every single home inspector should address at least the cleanliness issue with the client.”

Carpets are another primary source for microbial contamination. “If an inspector walks into a below-grade space and there’s a musty smell and the carpet looks like it’s been wet, it’s got to go,” says May. “Those carpets shouldn’t be washed; you can’t get rid of contaminants that way,” he explains. If in doubt, the home inspector should recommend that the carpet dust be tested for mold.

What tools can inspectors use when searching for mold?

A bright flashlight and a couple of mirrors (including an extending flame mirror with a glass mirror attached to the steel with double-stick tape) will be useful in hunting for mold on top of ceiling tiles, in dirty ducts and other tricky spaces. May also suggests using a non-invasive moisture meter that can check stains for dampness.

Should inspectors perform mold testing?

No, says May. “I would no more recommend that indoor air quality be a part of a pre-purchase home inspection than I would suggest someone with a brain tumor go to a heart specialist for surgery,” he says.

Searching for visible mold and air testing for mold are very different, May explains. Testing goes beyond the ASHI standards of practice and requires scientific training. Even if a home inspector has had such training and is able to test for mold, mold testing should not be part of the home inspection service.

Instead, May recommends that inspectors bring in a qualified expert to test for mold and other contaminants. Qualified is a key word here: “Moldy onions can cause high readings,” says May, or an inspector who has been in a moldy attic or crawl space in one home may carry spores into the next home he visits. “Bring in an expert,” says May, someone with experience who can not only detect the presence of mold, but can also determine what’s causing the problem and make recommendations for mitigation.

Visible mold is always a sign of an underlying problem, May concludes, but it is not the inspector’s job to identify the type of mold or determine if it is toxic. In May’s opinion, however, it is part of the inspector’s responsibility to supply his or her explanation as to why visible conditions might lead to excess moisture in the home.

Finding an Expert

After explaining that the ASHI Standards of Practice and Code of Ethics excludes indoor air quality issues, some inspectors would like to help their clients find additional information.

The Indoor Air Quality Association (, recommends hiring a company with qualified and certified staff that will be following industry standards and guidelines to ensure a job done right.

From the Home Inspector’s Point of View

OK, so you’ve discovered a moisture problem with some black stuff growing on it. What now? Is it really a health problem? Finding someone to give meaningful answers is not as easy as it seems.

First and last, remember that mold growth is a sign of a moisture problem. If the moisture problem is not identified and corrected, then the mold will just come back no matter what else is done. Finding the moisture source is the one area where home inspectors should be offering their customers some advice.

Beyond that I believe addressing the health effects of mold should be left to a professional.

— Garet Denise, ASHI technical committee chair

Consumers and home inspectors both may be interested in what the Center for Disease Control and the Environmental Protection Agency have to say about mold.

Mold and Your Health

Exposure to damp and moldy environments may cause a variety of health effects, or none at all. Some people are sensitive to molds. For these people, molds can cause nasal stuffiness, throat irritation, coughing or wheezing, eye irritation or, in some cases, skin irritation. People with mold allergies may have more severe reactions. Immune-compromised people and people with chronic lung illnesses, such as obstructive lung disease, may get serious infections in their lungs when they are exposed to mold. These people should stay away from areas that are likely to have mold, such as compost piles, cut grass and wooded areas.

For more from the CDC, visit


From “A Brief Guide to Mold, Moisture, and Your Home”

Testing or Sampling for Mold

Is sampling for mold needed? In most cases, if visible mold growth is present, sampling is unnecessary. Since no EPA or other federal limits have been set for mold or mold spores, sampling cannot be used to check a building’s compliance with federal mold standards. Surface sampling may be useful to determine if an area has been adequately cleaned or remediated. Sampling for mold should be conducted by professionals who have specific experience in designing mold sampling protocols, sampling methods and interpreting results.

Source: Written by Jennifer G. Prokopy for the ASHI Reporter (American Society of Home Inspectors)

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