Mold clearance testing: what passing post-remediation looks like

What is mold clearance testing?

Clearance testing, also called post-remediation verification, is the check that happens after a mold remediation crew finishes and before the work area is reopened. It answers one question: did the job work?

A clearance visit usually has three parts. First, a visual inspection inside the work area. Second, moisture readings on the materials left in place, such as studs and subfloor. Third, in many cases, air or surface samples sent to a lab.

The visit should happen while containment, the plastic sheeting and negative air setup that isolates the work area, is still in place. New York’s Department of Labor is explicit. The contractor may not remove materials or dismantle containment until you get a passed clearance report.

Clearance is not the same as the testing people do before remediation. The CDC does not recommend routine mold testing to find out what kind of mold you have. Clearance is different because it measures whether a specific cleanup succeeded. For the steps that come before it, see our guide to the mold remediation process, and for terms, see the clearance testing glossary entry.

What does “passing” look like?

No federal agency sets a numeric pass mark for mold. EPA’s remediation guide lists what success looks like instead:

• The water or moisture problem has been completely fixed.
• No visible mold, mold-damaged materials or moldy odors remain.
• If sampling was done, the kinds and concentrations of mold in the building are similar to those found outside.
• A return visit shows no new water damage or mold growth.
• People can occupy the space without health complaints or physical symptoms.

EPA itself admits there is “no easy answer” and that the final call involves judgment.

New York turns this into a document. Under the DOL process, the project is complete only when the assessor issues a passed clearance report. That report states the work area is free from all visible mold. It also confirms the work followed both the assessor’s remediation plan and the contractor’s work plan, and that the plan’s clearance criteria were met.

The industry standard, IICRC S520, describes the target as Condition 1, meaning normal fungal ecology for a similar clean, dry indoor space. A 2024 draft of the standard says completion should confirm a return to Condition 1. Remaining materials should be dry, and the area should be free of visible dirt, dust, debris, odors and mold.

Pass or fail: what the assessor checks

The criteria in the table come from EPA’s guidance, New York’s DOL process and the S520 draft cited on this page. Your assessor’s plan should list the exact criteria before work starts.

How to read air sample results

Most clearance air tests are spore trap samples. A pump draws a set volume of air through a cassette, and a lab counts and identifies the spores. The report usually lists spore types, such as Aspergillus/Penicillium or Cladosporium, with counts per cubic meter of air.

Three rules help you read it.

Compare, don’t judge one number. EPA says no federal threshold limits have been set for mold or mold spores. TDLR says standards for an acceptable quantity of mold have not been established. That is why a good report includes an outdoor control sample taken the same day, and why there is no single “safe” number.

Look at the types, not just the total. If indoor air is dominated by a type that is rare in the outdoor sample, that can point to a remaining indoor source even when the total count looks modest. The assessor should explain this in writing.

Samples are a snapshot. Weather, recent cleaning and air movement all change results. Air samples support the visual inspection and moisture readings. They don’t replace them.

If you can’t follow the report, ask the assessor to explain each line in plain language before you pay the final invoice.

Who should do the clearance test?

The person who checks the work should not be the person who did it. Three states with mold licensing put this into law:

• Florida. Under §468.8419, a mold assessor may not remediate a structure they assessed in the last 12 months, and a remediator may not assess a structure they remediated. Assessors and remediators also may not pay or accept referral compensation from each other.
• New York. Labor Law §936 bars any licensee from doing both mold assessment and remediation on the same property. The DOL FAQ says a remediator cannot work on a project without an assessment by a licensed assessor.
• Texas. TDLR says you may not conduct both assessment and remediation on the same project, and that clearance requires a post-remediation assessment by a licensed consultant.

In other states, licensing is usually not required, but the same logic holds. Hire an assessor who has no financial tie to the remediation company. Our guide to mold assessors versus remediators explains the two roles, and mold licensing by state shows where a license is required.

What happens if the area fails?

A failed clearance is not unusual. It usually means dust was left behind, a spot was missed, or materials are still damp.

In New York, the assessor issues a final status report that lists what needs to be done, for you and the contractor. The general sequence elsewhere is similar. The remediator re-cleans, fixes anything missed and dries remaining materials. Then the assessor tests again.

If an area fails twice, look harder at moisture. Clean surfaces on wet framing grow mold again. The assessor should check for a remaining leak, a missed wall cavity or high indoor humidity.

Settle the money question before work starts. Your remediation contract should say whether re-cleaning and the second clearance visit are included or billed separately. If the remediator refuses any clearance step, treat that as a warning sign. See how to choose a mold remediation company.

What paperwork should you keep?

Keep the full clearance report, the lab results, the assessor’s original remediation plan and the remediator’s work plan. These documents matter later for an insurance claim, a home sale or a dispute with a landlord or contractor.

Texas adds a formal document. Under Occupations Code §1958.154, the license holder must give the property owner a Certificate of Mold Remediation within 10 days after completing the work. An owner who sells the property must give the buyer copies of certificates issued in the five years before the sale.

If you live elsewhere, ask for a signed completion letter that names the work area, the dates and the criteria used. For typical prices of inspections and samples, see our mold inspection cost page. For more background, return to the mold hub.