Consider testing when any of the following apply:

1. You can’t find the source (hidden leaks/attic/inside walls) but occupants have symptoms — targeted testing can help locate hidden contamination.
2. Legal/insurance/real-estate reasons — to document conditions before/after remediation, for disclosure during sale, or when a dispute requires objective data. (Use a qualified industrial hygienist and chain-of-custody.)
3. Post-remediation clearance (QA) — when a professional remediation was done and you want proof the cleanup succeeded. The EPA and remediation pros note surface/testing can show whether an area was adequately cleaned.
4. Occupant vulnerability — immunocompromised people or medically complex households may warrant more rigorous investigation and documentation. (Medical advice should also be sought.)

What testing can — and cannot — tell you

• Can: show whether spores or colonies were present on a swab or captured in air at the sampling moment; help document before/after remediation; sometimes indicate likely source areas when used with a visual/thermal inspection.
• Cannot reliably: quantify health risk from a single short sample, provide a universally “safe” numeric threshold (no federal limits), or replace the need to fix moisture and remove affected materials.

Types of tests (brief)

• Visible surface sampling (tape/swab) — identifies what’s growing where. Useful for lab ID, but species ID rarely changes remediation decisions.
• Air sampling — snapshot of spores in air; highly variable and must be compared to outdoor baseline and interpreted by a pro.
• Bulk samples — pieces of material sent for analysis.
• ERMI (DNA-based index) — a research tool; EPA does not recommend ERMI for routine home testing.

Practical guidance if you do decide to test

1. Start with a thorough visual inspection and fix moisture first — most agencies (and state health departments) recommend inspection over routine testing.
2. Use a qualified professional (industrial hygienist or certified mold assessor) who follows recognized protocols (AIHA/ACGIH guidance) and uses an accredited lab. EPA emphasizes experienced samplers and appropriate analytical methods.
3. Collect outdoor baseline samples at the same time if doing air testing — helps interpretation.
4. Get chain-of-custody & a clear report that explains methods, limitations, and recommended next steps (not just spore counts).
5. Expect limitations: DIY home test kits and single short-term air samples are often misleading.

Quick decision checklist

• Do you see mold or smell musty odor? → Don’t test first — fix moisture and remediate visible mold.
• Is there a hidden problem or legal/insurance/medical reason? → Testing may be worth it — hire a pro and document carefully.
• Do you want proof after a paid remediation? → Post-remediation testing can be sensible QA.