Mold Testing

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The following is reprinted from Working RE Inspector, a nationwide print magazine exclusively for home inspectors. If you are not a subscriber, you can read the entire magazine here.

Mold Testing

By Edward Sobek, PhD

Home inspectors are on the front lines in the battle against mold in residential properties. Mold testing services have been around many years. Many inspectors avoid it while others dive in and tackle it, offering mold testing as an add-on service. On the other end of the spectrum, there are inspectors who have switched to inspecting for mold full time. Is testing right for you at this time? We think for many, the answer is yes.

Training and Testing
Providing complete mold/environmental inspection services can be extremely lucrative but requires additional training both on and off the job. However, inspectors can offer a simplified mold testing service without having to become a certified mold inspector. That solution is to provide a “Mold Screening Service,” that is designed to issue a black and white answer to the question of whether a residential property has a mold issue or not. It’s a relatively simple, high-profit add-on service that many buyers take advantage of when it is offered.

By now, the majority of inspectors have some general idea about mold, even if they have a disclaimer in their contract that excludes mold from the home inspection. There is no denying that that colorful fuzzy material in the crawlspace is mold. Still, many inspectors think it’s too risky to report it. One inspector told me that mold is like a landmine that is best to avoid, rather than risk a litigation “explosion” that could damage his company and livelihood. That is hard to argue with but that is exactly what I am going to do, because the risk of not reporting mold is more dangerous than any landmine. It’s more like a powder keg with a short fuse attached to a smoldering cigar—like in an old spaghetti western. That keg is going to blow and you have no way of knowing when or where or how much collateral damage is going to occur. So the best answer is to take control.

If you have more than 50 home inspections under your belt, you already have developed some intuition about mold. Simple things come to mind, especially related to water. Mold needs water or moisture to germinate and colonize indoor substrates. A house with a leaky roof, window, hot water heater, shower, etc. is going to have a mold problem; the extent of the problem depends on how large of an area the water intrusion is affecting and how long it has been going on. Larger and longer equals more mold, while a small area and shorter duration will equate to little or no mold. You’ve all spent time in dank basements and nasty crawlspaces where the humidity is out of check and that musky, moldy funk saturates your olfactory cells. You have seen the fuzzy surface mold in those areas that produce that odor. You’ve seen green, black and yellow blotches on drywall behind washers with leaky hoses. You’ve seen leather shoes in closets with a nice blue fuzzy covering that you know has nothing to do with fashion. You already have enough innate knowledge of mold to start screening.

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Safety First
Whether you decide to begin screening for mold or not, I urge you to start protecting your health during a home inspection. Too many inspectors refuse to use personal protective equipment on an inspection. You are the most important person in your business. If you get sick the bills go unpaid, you lose business, and your number one attribute—your health—is at risk of permanent damage. I recommend that you buy a box of comfortable N95 masks. Take some with you when you enter a home. Put the mask on immediately if you go into an area of a home like a basement where you can see mold or the air has a musky odor. Chronic exposure to high concentrations of mold may lead to a variety of health problems. Scientific studies have shown that chronic exposure to elevated mold indoors significantly increases the risk of adult-onset asthma. Chronic sinus infection is another documented outcome of continued mold exposure. It is called fungal sinusitis. Protection is key. Follow these three rules. 1) If you smell musky, dank odors, or see suspected mold growth on surfaces, put on your N95 respirator. 2) Always wear your N95 in non-living areas like crawlspaces and attics. 3) Be kind: if you’re going to put a N95 on and someone like an agent or homeowner is walking with you, always offer them one too. If they decline, the risk is on them, not you.

Mold Screening
I like to divide mold screening into conditioned and non-conditioned spaces. Conditioned space is living space. It is where occupants spend most of their time: bedrooms, dens, living rooms, kitchen etc. Unconditioned spaces have no heat and air, like crawlspaces, attics and garages. The objective of a mold screening service in the living space is to determine if the airborne concentration of mold is elevated. Since you’re going to be going through the entire house for your standard inspection, it’s easy to combine the mold screening service at the same time. You are going to collect air samples in the conditioned space to determine airborne mold spore concentrations. You will also collect an air sample outside of the house to compare to the indoor. In non-conditioned spaces, only collect samples from surfaces that you believe have suspect surface mold. Do not collect air samples in a crawlspace; it’s not a living space and will only end up confusing all parties involved. Too many factors outside the control of the homeowner can lead to airborne mold in a crawlspace. Always use the phrase “Suspect Surface Mold” when discussing visible mold. That dark area could be a cola stain; it could be anything. Never state that “surface mold is present” unless and until you have a confirmation report from a laboratory accredited by the American Industrial Hygiene Association (AIHA).

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For those home inspectors eager to add a mold screening service, they first need to find a home inspector friendly AIHA-accredited laboratory (such as Assured Bio Labs, LLC.). Look for one that caters to inspectors, that teaches courses approved in your state, and has technical field scientists on staff who conduct high-end residential and commercial mold investigations. Second, you are going to need a sampling kit that includes a sampling pump, tripod, swabs, air cassettes etc. The lab will set you up with everything you need.

Air Sampling
To determine if mold is at elevated levels indoors, the indoor airborne mold concentration is compared to the outdoor concentration. Higher concentrations of water-intrusion mold inside equates to an elevation. However, for reliability, a representative air sample is required. A single location inside plus a single location outside is not adequate. A composite sample of the whole living space, from multiple locations, is required and likewise a composite sample of the outside air surrounding the home is necessary. Subsampling using mold testing kits both inside and outside gets the job done. It provides a single composite inside sample to compare to a composite outside.

I recommend that you subsample five locations in a home with a standard mold testing kit, although the procedure may vary depending on the test kit you are using. That will provide a robust representation of the air inside the home. With another mold test kit, collect a composite outside sample from three or four locations around the home. Remember you are just screening. If mold is elevated anywhere in the house it is a problem. You are not sourcing the mold reservoir.

Unconditioned spaces are easy. These are samples collected with special swabs from surfaces where you suspect mold colonization. For example, if sampling a crawlspace you do not need to sample every spot, just a representative area, and the same goes for attics. Note the locations sampled. Also estimate how much suspected mold is present in the unconditioned space. Is it 10%, 50% or 95% of the cross beams in a crawlspace? If the laboratory data confirms that your samples are mold, then report the concentrations along with how much of an area the mold is colonizing and the locations sampled.


How much should an inspector charge for the screening service? Let’s do some numbers. In general, the supplies and analysis are going to run about $125 to $150 dollars per screening. Also take into account the initial equipment setup cost and annual cost of E&O insurance (mold testing can be added very inexpensively with most insurance programs, such as OREP’s). Also consider your market. Are you working in Nashville on million-dollar homes or in the average American suburb? A larger home is going to require more subsamples to obtain a representative composite. For the average 2,000 square foot home I recommend $295 on the low end up to $375 on the high. Remember, you are not offering a mold inspection but a screening service. It’s a huge difference, so make sure the client understands that in writing.

The objective of a mold inspection is to 1) document the location(s) of the mold contamination in the residence, 2) identify the root cause of the contamination, 3) write a detailed remediation protocol in order to remove the mold, stop the source of moisture, and restore the home back to a balanced healthy environment with respect to mold concentrations, and 4) conduct post-remediation verification testing to ensure that the remediation protocol was completed successfully. Mold screening, on the other hand, is only designed to determine if a home has an elevated mold condition or not. A complete mold inspection on the same size house is going to range from $850 to $2,000, depending on the market. That should not discount the value of a screening. For a relatively modest amount of money, your client is receiving a high-value service that they can count on to make an informed decision that involves a large sum of money tied up in the home.

Mold screening, on the other hand, is only designed to determine if a home has an elevated mold condition or not. A complete mold inspection on the same size house is going to range from $850 to $2,000, depending on the market. That should not discount the value of a screening. For a relatively modest amount of money, your client is receiving a high-value service that they can count on to make an informed decision that involves a large sum of money tied up in the home.



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About the Author
Edward Sobek is a PhD microbiologist with 20 years of laboratory and field experience. Dr. Sobek specializes in microbial and chemical issues affecting the built-environment. He and his team at Assured Bio Labs have tackled everything from viral outbreaks in medical facilities, moldy manufactured plastics, Legionella investigations to formaldehyde off-gassing in building materials. They have diagnosed mold and bacteria issues in hundreds of homes, commercial properties and complex manufacturing settings. He has worked on odor and chemical contamination in both residential and commercial properties. Dr. Sobek is also the founder and President of Assured Bio Labs, LLC. Assured Bio is an AIHA accredited and CDC Elite laboratory. Home inspectors prefer Assured Bio Labs because of their friendly and knowledgeable staff, superior technology and fast turnaround time.



Note: The following story is from Working RE Inspector, a new print magazine exclusively for home inspectors. If you missed the print issue, you can read it here.
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One Comment

  1. by Brian Lehman WA State Licensed Inspector #305

    After 12 years of inspecting home’s I noticed that like most articles extolling mold testing it is not mentioned anywhere that there are no recognized limits on what does and does not constitiute air quality of concern and the worlds leading health organizations such as the EPA, the CDC and the WHO do not recognize mold as a health hazard to healthy people and do not recommend residential mold sampling. I recently found a very large batch of visible mold in a house that had just been declared “safe and mold free.” The people who paid for the supposedly “legitimate sampling” are now finding out that the inspector is simply a well paid messenger and the labs that produced the results have of course protected themselves accordingly. Theyve been ripped off over what could be a health related issue but have no recourse because of course there are no legitimate guidlines or laws concerning mold. Hard to take any of these articles seriously because they are generally much more of a shill for the mold testing industry than an actual unbalanced look at mold sampling.

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