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The Art of inner Wall Sampling II



If spore levels in a given wall are significantly higher than outdoor air or indoor room air, then it is logical to conclude that the mold spores in that wall cavity's air likely came from growth in the wall cavity. This is the same methodology used to draw conclusions from air sample results taken from room air that is then compared to an outdoor air sample.

Based on this inspector's experience obtaining thousands of inner wall samples and room air samples and outdoor samples all over Southeast Florida since 2003, I have observed the above premises to be true. If inner wall air samples have spore levels higher than outdoor levels or higher than room air levels than mold is likely growing in the wall.

Most walls without water damage and without likely mold problems typically will have spore types and levels similar to those found in the indoor room air. In many cases the levels in the walls are lower than room air levels.

Walls without water damage or mold problems often have very low spore levels, even lower than the levels in a typical healthy home because in a typical healthy home free of unusual mold problems we still have mold in flower pot soil, on refrigerator gaskets, in shower grout, and under the rim of toilet bowls, and inside toilet tanks, in dusty carpets, in garbage cans, aquarium filters, and window sills, and do not forget that old potato in the vegetable crisper in the bottom of the refrigerator. All this typically ads up to about 50 to 500 spores per cubic meter of air in a health home without water damage or mold problems.

Most inspectors agree that inner wall sampling is effective, but I have heard of one ocassion where an adjuster from the insurance company did not want an inspector to find mold, and he argued that debris inside a wall may cause mold spore readings in that wall to be elevated even if a mold problems was not caused by a leak that was covered by insurance. This is a stupid argument. No matter how much debris you have in a wall, you will not have mold without a leak.

When we look inside a typical non water damaged wall, we find drywall that was clean and dry as a bone when it came from the manufacturer. And when it was installed in the home the roof was already up and the windows and doors were typically already installed, thus the interior of the walls are not full of pools of rain water from the construction period.  If you do not believe me look inside a hundred walls with borescopes, and look inside a hundred walls cut open with a drywall saw and you will see that the interior of non water damaged walls is typically clean, free of mold, moisture stains, and free of excess debris. 

You may find an occasional Coca Cola can, or drill bit, or some saw dust, or a cut and discarded wire segment in the bottom of the wall void, but these items do not breed mold. The limiting factor for mold growth is and has always been water in the built environment. This fact is drilled into every mold inspectors head in the first day of every basic simplistic mindless 2 day mold inspection certification course. In other words mold will not grow in a wall or in a home or anywhere else in the lack of water. In fact any microbioligis or other biologist with an associates degree or PHD will agree with this teaching and tell you that neither mold, nor any other living thing on the planet will ever grow in the absence of water. They will admit that a wall or a soda can, or sawdust, or cut wires in a wall, will not and cannot support mold growth until water is added. In other words mold will not grow on a dry Coca Cola in your wall no more than it grows on Coco Cola cans at the grocery store shelf. It will not grow on dry saw dust in a wall no more than it will grow on dry wood on your dining room table.  

You are less likely to obtain a false positive test result in a wall than in a home, this is based on 8 years of sampling home air and inner wall air. It is also based on the simple fact that in a healthy home dozens of wet and humid mirco niches exist for mold to grow in, as stated above in the condensation of a refrigerator gasket, and in the grout of a shower, or the tank of a toilet. But in a wall, unless a leak occurs the inside of a 20 year old wall has been dry and dead for 20 years.

When the inside of walls with moisture damage, visible mold, moisture stains, or mold odors are tested, then the spore levels are elevated inside that wall and spore types are often altered. Analyzing spore levels and types in a wall to determine if unusual mold conditions exist in that wall is far more clear cut than analyzing room air, in this inspector's opinion and experience. 

If you analyze the air in a moldy home you may come up with a false negative, (the lack of spores despite the presence of mold, this occurs often when a home seller paints over water damage and mold the day before the inspection. A home seller no matter how tricky is not going to paint over mold growing inside that wall that you are sampling from. 

A realtor may open all the doors and windows prior to an a mold inspection, because they did not know they should keep the doors and windows shut in order for you to sample the indoor air, at least this is the excuse the Realtors always give me when I ask why they opened the doors and windows prior to an inspection. But a realtor cannot open the doors and windows and alter the concentrations and types of spores in that wall that your mold testing specialist is sampling from.   

In a wall with mold problems, inner wall spore levels are often obviously elevated, while in a moldy room spore levels can be unusually low if the air in that room is still and spores have settled due to the property being vacant, such as in the case of a neglected foreclosure property.

In a room with water damage indicators such as Chaetomium or Stachybotrys mold spores, the mold and its spores are very often trapped in a water-damaged wall, and the spores will not show up in an air sample at all. We call this a false negative, and this is extremely common. 

If you are lucky, then one or two spores from inside a moldy wall will escape from the wall and show up in your mold inspector's spore trap, but then with such low levels it will remain unclear if the mold that produced it was a very tiny growth on a nearby carpet or baseboard producing small numbers of spores, or if the few spores recovered is the tip of the iceberg and indicative of massive amounts of mold growing in the wall on the opposite side of the room from the spore trap.  If the mold tester sampled from inside the wall then he or she would know exactly what wall that mold came from and how many spores per cubic meter of air cam from inside the wall.

Thus sampling air will often give false negatives if the mold is hidden, and will often give limited information if it gives a positive.

In the same room with mold growing in a wall, the mold and its spores are very often trapped, and sampling air from within that wall with millions or trapped spores will often, without any ambiguity, reveal clear evidence of a mold problem in that wall. Such a sample will not only tell you that you have mold, but now you have information on exactly what wall that mold is located in. While when finding spores in the air you know you have spores but you do not know where that came from.  

Based on this inspector's experience, inner wall sampling is a very effective method of determining if mold is growing in a wall. In a legal dispute some people will try and argue with the simple logic behind inner wall sampling. Click here: you can find arguments against people who do not want to admit that an inner wall sample can indicate mold in a wall.

The owner of a fine mold lab in Pompano Beach Fl once told me that lots of people sample from inside walls, but that some people believe that it is pointless and their argument is that " if mold is trapped in a wall then it is not important to sample in that wall to prove it's existence because the mold is trapped so who cares anyway.

My answer was that such trapped growths can still release microbial volatile organic compounds or mold odor that escape from inside the wall very easily and these MVOC's cause adverse health reactions. It is a fact that studies show that exposure to these odors or MVOC's doubles a child's chances of developing asthma even if the odors are present and the spores are not. I have seen countless instance where mold in a wall release mold odors via electrical outlet openings or by other means.

I have also observed that in such cases where smelly mold is in a wall, persons in such an environment become ill even though sampling the air reveals no mold spore issues, while sampling the air in such walls will reveal highly elevated spore levels and thus is a more reliable tool for determining if mold problems that might have a correlation to health complaints may exist.  

To maximize the chances of finding hidden mold problems, inspectors often sample the air from the center of a room, or from near an AC return that may be pulling air into the AC system from that room, or even from all areas of the entire property.