What is ERMI and should you do wall cavity testing?
March 2018: By Susan Browne Rosenberg, CIH, CIEC (expired 02/2020), CHMM
President, Desert Cities Indoor Air, LLC
ERMI is an acronym for a tool developed by the EPA to evaluate homes using something called the Environmental Relative Moldiness Index. It is a process used to enumerate “the moldiness” of a home. Briefly, dust from carpet and floors is vacuumed into a collection device attached to a handheld vacuum like a Dust Devil. The lab needs about a tablespoon of this dust for analysis. The protocol specifies that by collecting dust from multiple rooms you can determine the baseline moldiness of a home.
ERMI was developed in 2007, by the EPA and U.S. Department of Housing and Urban Development researchers. These researchers decided that 36 mold species (out of the thousands of mold species out there) were sufficient to describe the mold burden (“moldiness”) of a home. As part of the HUD-sponsored American Healthy Homes Survey, dust samples were collected from a nationwide random sampling of 1,096 homes and analyzed by MSQPCR (Mold Specific Quantitative Polymerase Chain Reaction), a DNA-based method of mold analysis, for the 36 indicator species. The ERMI values were then calculated for each of the 1,096 homes. The values were assembled from lowest to highest and divided into quartiles. The values ranged from -10 to 20. Theoretically, if the dust from your house scores in the red (bad) zone, you have a moldy house.
The EPA designed this as a research tool, and then licensed the protocol for analyzing the samples to a handful of labs across the US. So mold labs that had the license began marketing to consumers who were told that they “needed” this test. For several years, these labs made quite a bit of money providing this service. Then, in 2013, the US EPA Office of Inspector General issued a response to complaints that companies were using the tool inappropriately and that “the EPA had not validated the tool for public use.” ¹
Today, there are still doctors who are telling their patients to get this test because the doctor believes that mold may be causing such symptoms as lethargy, headaches and other non-specific aches and pains. If you are interested in reading the entire report titled “Public May Be Making Indoor Mold Cleanup Decisions Based on EPA Tool Developed Only for Research Applications”, you can find it by clicking the link below.
The big problem with the ERMI test in my opinion (besides not being validated and being used inappropriately), is that the test does not tell you where the mold problem is or how to resolve the problem. You still need a visual inspection, moisture tests and a professional Indoor Environmental Consultant to make a house call and see what is really happening in your home. So why waste money? An ERMI test can cost hundreds of dollars.
Another type of testing that I do NOT recommend is wall cavity testing. I have used this technique on rare occasions during my 20 years of experience, but have come to the conclusion that it is often biased and can give misleading results. To test a wall cavity one must either drill a hole in the wall or test at an electrical outlet or phone conduit that can be opened up. An air sampling pump is then connected to a piece of tubing that sucks air from inside the wall. However, if a hole was drilled for access, then the interior wall cavity will be filled with drywall debris which can obscure any mold spores. Therefore, drilling should never be done prior to sampling.
I have seen the interior wall cavities of thousands of buildings, and let me tell you one thing is for certain – wall spaces are anything but clean and mold free. There can be dead animals, empty beer bottles and soda cans, spider webs, leftover pieces of drywall, and other garbage. If the wall is dry and there is no evidence or suggestion of water intrusion from plumbing leaks, I recommend that you should leave it alone. If the visual inspection shows wet walls or suspect visible mold growth on the wall inside your home, then there is most likely mold growth inside of that wall. How much and what should be done depends on the size of the leak.
If your neighbor’s adjoining wall is wet and has mold growth, should you be concerned about the interior of your apartment or condo? Absolutely! However, please remember that each case is different and each response should be tailored to the situation at hand. Before you take any rash steps, please contact Desert Cities Indoor Air for a free ten minute phone consultation to discuss your concerns and questions.