The Environmental Relative Moldiness Index (ERMI) is an indoor air quality testing method developed by the U.S. Environmental Protection Agency (EPA) in collaboration with the U.S. Department of Housing and Urban Development (HUD). ERMI was designed to provide a sensitive and standardized way to assess air quality and mold contamination in homes. This method involves collecting dust samples from various locations within a home, which are then sent to a laboratory for DNA-based analysis to differentiate and quantify specific mold species present in the samples. The laboratory calculates an ERMI score by comparing the concentrations of different mold species in the samples to a national database of mold species concentrations from homes across the U.S.
The ERMI score helps predict the moldiness of a home and assess the potential risk of indoor mold growth and associated health effects. This standardized and objective method provides a comprehensive analysis of mold contamination, allowing homeowners to understand the potential health risks and take appropriate remediation measures.
In order to most effectively use this new tool, the ERMI must be compared to a national database. Indices were determined using this method for 1,096 homes across the U.S. as part of the 2006 HUD American Healthy Home Survey. Individual indices, ranked from lowest to highest were used to create a national Relative Moldiness Index (RMI) Scale.
- How Does ERMI Work?
The ERMI test involves the analysis of a single sample of dust from a home. The sample is analyzed using mold-specific quantitative polymerase chain reaction (MSQPCR), a highly specific DNA-based method for quantifying mold species. A simple algorithm is used to calculate a ratio of water damage-related species to common indoor molds and the resulting score is called the Environmental Relative Moldiness Index or ERMI. The ERMI value is typically between -10 and 20.
- How are samples collected for ERMI testing?
ERMI testing depends on settled dust, which behaves as a mold breeding ground. The ERMI sample is a combined sample of dust, typically taken from the living room and master bedroom. The required dust samples can be obtained by vacuuming about 2 square meters each of the bedroom and living room carpet for five minutes each. The outdoor control is integrated into the ERMI sample.
- How can we best utilize ERMI Scores?
During a mold and moisture inspection an ERMI analysis offers data useful to assist in the assessment of the home by a qualified professional. If the ERMI score indicates that there may be water damage in the house, further detailed inspection, including additional testing such as bulk or mold swab testing may reveal a concealed source of water damage and/or mold.
- Does living in an environment with a high ERMI score cause health issues?
There are no explicit guidelines for human health with an ERMI score. The symptoms of mold exposure vary from person to person, depending on the sensitivity of each individual and their degree of mold exposure. The ERMI score should be used in combination with individual mold species quantifications and symptoms of home occupants in order to make a decision. The ERMI score is simply a guideline for the determination of mold exposure levels for home occupants.
Drawbacks of ERMI Mold Testing
While the Environmental Relative Moldiness Index (ERMI) is a useful tool for assessing mold contamination, it has several limitations that should be considered:
- Limited Scope: ERMI testing primarily focuses on dust samples collected from carpets, which may not provide a comprehensive assessment of mold contamination throughout the entire building. This method may miss mold growth in other areas, such as walls, ceilings, and HVAC systems.
- Lack of Standardization: There are no standardized guidelines for interpreting ERMI scores, making it challenging to determine what constitutes a “safe” or “unsafe” level of mold contamination. The ERMI score is based on a comparison to a national database, which may not accurately reflect the specific conditions of an individual home or building.
- Potential for Misuse: ERMI testing was initially designed for research purposes and may not be suitable for routine mold inspections. The EPA has advised against using ERMI scores as the sole basis for making decisions about mold remediation
The Environmental Protection Agency (EPA) does not recommend the routine public use of the Environmental Relative Moldiness Index (ERMI) for homes, schools, or other buildings because it was developed as a research tool and has not been validated for non-research purposes. The ERMI scale was designed to estimate mold contamination levels for research studies, and its application in routine mold inspections may not provide accurate or reliable results. Therefore, the EPA advises against using ERMI scores as the sole basis for making decisions about mold remediation
Inability to determine current conditions
Unlike air sampling, the ERMI test uses settled dust as the sample material which doesn’t necessarily tell us about the current conditions. It may be hard to know how much time has passed since the last time the sampled surface was cleaned. Has it been 3 weeks, or maybe 3 months? The difference in time could be significant, which would naturally produce different results. Let’s say a home hasn’t had any mold problem for the last 2 months. However, there was a 3-day period 3 months ago when many mold spores were released while the property owner opened a moldy tent within the home to dry it out. Perhaps the outside air had a high amount of mold spores for a week and the windows were left open. Clearly, the elevated mold spores were not part of the ongoing mold issue. But they’re still going to show up in the ERMI sample.
Challenges with interpreting test results
Another challenge related to ERMIs is difficulty in interpreting results. One of the main issues is how the formula treats outdoor spores. The formula separates the mold spores that usually grow outdoors from those that are associated with water damage. Unfortunately, this is a difficult distinction to make. Cladosporium, for instance, is one of the most common forms of mold growth found in places with existing indoor water damage. Yet the ERMI formula positions it as an “outdoor mold spore.” Cladosporium is a ubiquitous mold found both indoors and outdoors. Thus, if a home had significant levels of Cladosporium growing indoors, it would simply be subtracted from the data and the house would achieve a clean bill of health.
Conclusion
ERMI testing definitely has its place if used strategically. ERMI testing can be useful in trying to ascertain the long-term history of a house and an overall sense of the quantity of settled mold spores in the home. ERMI testing is a viable option for defining mold built up by offering comparable information to a baseline from which to start or support a more thorough investigation.
CALL US TODAY to schedule a mold inspection for your home or office in Raleigh, North Carolina. There is never a wrong time to test your property for mold, and it can save you thousands in the future.
