A remediation contractor calls and asks you to "pass" the job. There is no single number you can read off a meter to do that, and an inspector who treats clearance as one air sample is missing most of the standard.
What is post-remediation verification sampling?
Post-remediation verification (clearance) is the independent assessment that confirms a remediated area is visibly clean, dry, and free of a moisture source before reoccupancy — with air sampling used as supporting evidence, not the sole verdict. IICRC S520 addresses post-remediation verification as a multi-part judgment, not a single threshold (IICRC, S520).
The key word is multi-part. A clearance that rests only on an air count ignores the parts the standard weights most heavily: the visual inspection and the moisture condition. Air sampling supports the conclusion; it does not produce it on its own.
What does a clearance actually require?
Three things, in order: a visual inspection showing no remaining visible mold or dust, confirmation the materials are dry and the moisture source is corrected, and — where used — air results that no longer show indoor amplification against a same-day outdoor control. The EPA's clearance logic centers on the area being clean and dry, not on hitting a spore number (EPA, Mold Remediation in Schools and Commercial Buildings).
Order matters because a failed visual ends the clearance before you ever run a cassette. If visible debris or growth remains, no air count "passes" the job — you have already failed. Only after the visual and dryness checks pass does air sampling add its supporting evidence. The air comparison itself follows the logic in interpreting indoor:outdoor ratios.
Why isn't there a pass/fail spore count for clearance?
Because no authority publishes one. The EPA and CDC both decline to set an acceptable airborne mold concentration, so clearance cannot be keyed to a threshold that does not exist (EPA, Mold Remediation in Schools and Commercial Buildings; CDC, Mold: Basic Facts). The defensible reading is comparative: post-remediation indoor air should look like, or better than, the same-day outdoor control, with no remaining indicator-species amplification (AIHA, Green Book).
This is why "the count was under 1,000 so it passed" is an indefensible sentence. There is no 1,000 line in any standard. The result is the relationship between the cleared space and outdoors, plus the visual and dryness findings, taken together. Anyone reciting a fixed clearance number is inventing it.
Who should perform the clearance?
An independent party, not the company that did the remediation. Verification by someone with a financial stake in passing the job undercuts the credibility of the result, and independence is the recognized expectation for a defensible clearance (IICRC, S520; AIHA, Green Book).
That independence is the whole value of a third-party clearance. The remediator is motivated to close the job; the verifier is motivated to confirm the work, which is why a separate, documented assessment carries weight with insurers, occupants, and in disputes. Document the visual findings, the moisture readings, the sampling rationale, and the outdoor comparison so the clearance stands on its own.
MoldMind structures the clearance as its own report type — visual findings, moisture confirmation, the air comparison against outdoors, and the independence note — so the pass rests on the full standard rather than a single number. See the sample report and post-remediation clearance criteria.
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Sources
- IICRC, S520 Standard for Professional Mold Remediation — post-remediation verification as a multi-part, independent assessment.
- EPA, Mold Remediation in Schools and Commercial Buildings — clean-and-dry clearance logic; no spore threshold.
- CDC, Mold: Basic Facts — no acceptable airborne mold level established.
- AIHA, Green Book — comparative interpretation against the outdoor control.