'/%3e%3c!--%20Compass%20outer%20ring%20--%3e%3ccircle%20cx='128'%20cy='128'%20r='80'%20fill='none'%20stroke='%23ffffff'%20stroke-width='8'%20opacity='0.25'/%3e%3c!--%20Compass%20needle%20-%20North%20(gold)%20--%3e%3cpath%20d='M128%2056%20L144%20128%20L128%20116%20L112%20128%20Z'%20fill='url(%23accent)'/%3e%3c!--%20Compass%20needle%20-%20South%20(white)%20--%3e%3cpath%20d='M128%20200%20L144%20128%20L128%20140%20L112%20128%20Z'%20fill='%23ffffff'%20opacity='0.85'/%3e%3c!--%20Center%20circle%20--%3e%3ccircle%20cx='128'%20cy='128'%20r='12'%20fill='url(%23accent)'/%3e%3ccircle%20cx='128'%20cy='128'%20r='6'%20fill='%230d4a4f'/%3e%3c/svg%3e){kind=small}
Quick Answer
ERMI dust testing analyzes DNA from settled dust to estimate longer term mold burden. Air testing samples airborne spores and fragments at a single point in time.
Neither replaces a moisture investigation. Use testing when you need documentation or verification, not as a substitute for inspection.
What ERMI Measures
ERMI stands for Environmental Relative Moldiness Index. A dust sample is analyzed for a panel of mold species using DNA based methods. Results provide an index score based on the mix and quantity of molds in settled dust.
- Measures settled dust, not live growth
- Reflects longer term exposure history
- Useful when air testing is inconclusive
What Air Testing Measures
Air testing uses spore trap cassettes to capture airborne particles. Results are reported as spores per cubic meter and compared to an outdoor control sample.
Learn more about air sampling and how to read results.
- Measures airborne spores and fragments
- Snapshot that changes with activity and weather
- Best when paired with an outdoor control sample
Strengths and Limits
ERMI Strengths
- Captures longer term dust history
- Useful when there is no visible growth
- Can highlight water damage mold groups
ERMI Limits
- Does not show where mold is growing
- May reflect past issues already resolved
- Can be skewed by recent cleaning or dust levels
Air Testing Strengths
- Good for clearance testing after remediation
- Shows airborne exposure conditions
- Useful for documentation when symptoms persist
Air Testing Limits
- Highly variable snapshot
- Hidden mold can be missed
- No federal exposure limits for interpretation
Best Use Cases
Use ERMI When
- You need a longer term indicator of mold burden
- Air tests are normal but symptoms persist
- You want a baseline before moving into a home
Use Air Testing When
- You need post remediation verification
- You need comparison to outdoor levels
- You need documentation for a claim or dispute