Post-Remediation Verification in Portland, OR: How to Confirm Mold Cleanup Worked Before You Rebuild

What verification is and why it matters

Remediation removes and cleans. Verification asks whether it worked. The two are separate questions, because a thorough cleaning does not prove that the moisture is gone, and a dry wall does not prove that the cleaning was complete. The EPA's guide for larger buildings has a section titled "How Do You Know When You Have Finished Remediation/Cleanup?" and its first criterion is the one the rest depend on: you must have completely fixed the water or moisture problem.

The remaining criteria, in the EPA's order, are these. Visible mold, mold-damaged materials, and moldy odors should not be present. If sampling was done, the mold types and concentrations indoors should be similar to those outside. The site should be revisited shortly after remediation and show no signs of water damage or mold growth. And people should be able to occupy or reoccupy the space without health complaints or physical symptoms. The EPA closes the list with the sentence that ultimately this is a judgment call; there is no easy answer.

The reason this matters to a homeowner is the rebuild. Once drywall, insulation, and flooring go back over a surface, a missed patch or a still-damp stud is hidden again. Verification is scheduled between the cleanup and the rebuild for that reason. The cleanup steps themselves are on the remediation page.

What a verification visit includes

A thorough one has the same parts whether or not samples are taken.

1. 1

   Review the scope and the source

   The verifier reads what was supposed to be done, what the original inspection found, and what was fixed. The first question is whether the leak, condensation path, or drainage problem was corrected. OSHA states that the underlying cause of water accumulation must be rectified or the mold growth will reoccur.

2. 2

   Walk the area with the lights on

   A visual inspection of the cleaned surfaces, framing, subfloor, and adjacent areas, with good light. The New York City health guidelines call for work areas to be left dry and visibly free from contamination and debris.

3. 3

   Take moisture readings

   Readings on framing and subfloor are compared to dry reference points. A moisture meter, and sometimes a thermal camera, show whether anything is still damp. The instruments are explained on the inspection page.

4. 4

   Check odor and dust

   A musty smell inside the cleaned area, or fine dust left on surfaces, shows that cleaning was incomplete. The New York City guidelines call for HEPA vacuuming and damp cleaning of the work area, with barriers removed only after it is visibly clean.

5. 5

   Look at the places mold travels

   Adjacent rooms, the HVAC supply and return openings, and the area outside the containment are checked for dust or growth.

6. 6

   Decide whether to sample

   Sampling is a choice made for a reason, described below.

7. 7

   Write the report

   The report lists what was checked, the readings, photographs, and any open items, with a clear statement of whether the area is ready to be closed up.

When sampling is used, and when it is not

There are no federal standards or recommendations, from OSHA, NIOSH, or the EPA, for airborne concentrations of mold or mold spores. NIOSH adds that there are no health-based standards for mold or other biological agents in indoor air. A lab result therefore cannot be compared to a legal limit. It can be compared to the outdoors and to the condition before the work.

The EPA says that in most cases, if visible mold growth is present, sampling is unnecessary, and that sampling should be conducted by professionals with specific experience designing mold sampling protocols. It describes sampling as something that may be considered in specific cases: when litigation is involved, when the source of the contamination is unclear, or when health concerns are a problem. It also says surface sampling can help show whether an area was adequately cleaned, and that pre- and post-remediation sampling may be useful in determining whether remediation efforts have been effective.

The New York City guidelines are more specific for larger jobs. For work at their Level IV, extensive contamination of more than 100 contiguous square feet, they say air monitoring should be conducted prior to occupancy to determine whether the area is fit to reoccupy. The guidelines make a similar recommendation for some HVAC remediation, with the system operating. For smaller levels the guidelines rely on visual confirmation, and they note that air sampling should not be part of a routine assessment because decisions can usually be made by visual inspection, and because air-sampling methods for some fungi are prone to false negative results.

So the practical rule is this. For a small, visible job with a clear cause, a visual and moisture verification is the proportionate check. For a large job, a job in an occupied home with an immunocompromised person, a dispute, an insurance or lender requirement, or an unclear source, sampling adds information. The sample types, what a lab report contains, and how to read one are on the inspection page; this page covers what is specific to clearance.

The outdoor comparison

Mold spores are in outdoor air all the time. A clearance result is only meaningful against that background. The New York City guidelines say that air samples should be evaluated by comparison, indoors to outdoors and by fungal type, and that outdoor samples should be collected at the same time as indoor ones. The EPA's criterion states the same idea: indoor types and concentrations should be similar to those outside.

Two details follow. First, the comparison is by type and concentration, not by total. An indoor sample dominated by one type that is scarce outdoors reads differently from one whose mix mirrors the yard. Second, the outdoor sample should be collected the same day, at the same time, because spore counts shift with weather and season. A result taken after a dry week and compared to an outdoor sample from a damp morning is not a fair comparison.

The New York City guidance also says that the presence of few or trace amounts of fungal spores in bulk or surface sampling should be considered background. Microbial labs can be accredited by the American Industrial Hygiene Association's EMLAP program, and the New York City guidelines say accredited labs must take part in quarterly proficiency testing. Ask which lab will be used and what the sample type means before paying for one.

Who should do the verification

The simplest arrangement has one party do the cleaning and another check it. The party that cleaned has an interest in a pass, so many owners and many consultants prefer a separate assessor. That is a practice, not a rule: neither the EPA guide nor the New York City guidelines forbid a contractor from inspecting its own work. The EPA says a remediation manager uses professional judgment and experience to adapt the guidelines to particular situations, and tells readers to consult an experienced remediator.

The American Council for Accredited Certification (ACAC) certifies Certified Microbial Investigators (CMI) and Consultants (CMC). Its website says certified individuals can perform mold inspection, testing, and bioaerosol sampling, interpret lab results, design a remediation protocol, and perform post-remediation sampling to verify the success of a remediation project. The council lists a passing exam, field experience, and recertification every two years as requirements. If you want an independent check, ask any candidate which credentials they hold and who pays them.

Whoever does it, ask for the same things: a written scope, photographs, readings, a lab report if samples were taken, and a plain statement of the result. Also ask whether they have a financial interest in the remediation and what they would do if the result is not a pass.

If the result is not a pass

A failed or marginal result is information. The usual causes are narrow. The moisture source was not fully fixed, so the area is damp again. A patch was missed behind a framing member or on the back of a panel. Dust from the work was not fully removed, which can raise a count even when growth is gone. Adjacent areas were affected and not cleaned. Or the HVAC system is carrying spores. The fix follows the cause: repair the moisture source, re-clean the missed area, HEPA vacuum and wipe the dust, or clean the system. Then the area is checked again.

Agree beforehand who pays for re-cleaning if a failure traces to the original scope. The contract should say so. If the contractor has met the scope but the verifier finds a new source, such as a second leak, that is a new scope.

Keep both reports. A failed first visit followed by a passed second visit, with the cause named, is a better record than a single clean result with no history.

Timing, records, and what verification is used for

Verification happens before the area is covered. Once insulation, drywall, or flooring has been installed, the surfaces cannot be checked without opening them again. In a crawl space, an attic, or a wall cavity, that means the visit is scheduled when the cleaning and drying are done and before the rebuild trades arrive.

The report has uses after the job. Insurers and lenders may ask for it, and it is useful if the house is sold. Oregon's seller's disclosure form, ORS 105.464, asks whether there are moisture problems, areas of water penetration, or mildew odors, and whether the property has been tested or treated for mold, and warns buyers to obtain and pay for a qualified specialist to inspect. A clear record of the problem, the fix, and the verification answers those questions with documents. Whether and how to disclose is a question for the seller's agent or attorney.

The EPA's "revisit shortly after" criterion is a reminder that the check does not end on the day of the visit. After the work, keep the humidity in range, watch the area during the next heavy rain or cold snap, and call if a smell or a stain returns.

What affects the price of verification

Cost follows the visit, the samples, and the report.

• Size and number of areas More rooms, attic, crawl space, and ductwork mean more time.
• Access A tight crawl space or attic takes longer to inspect.
• Sampling Each air or surface sample has a lab fee, and a job may need indoor, outdoor, and comparison samples.
• Lab turnaround Faster results cost more.
• Report detail A short pass-fail letter differs from a full report with photographs, readings, and a lab interpretation.
• Re-checks A second visit after a failed first one is normally its own charge.
• Independence A separate assessor is a separate engagement, apart from the remediation contract.

Questions to ask about verification

These clarify what you are buying before the visit.

1. What will the verification include: visual, moisture readings, odor, sampling?
2. Who will do it, and do they have a financial interest in the remediation?
3. If you sample, what sample types will be taken, how many, and where?
4. Will you collect outdoor samples on the same day?
5. Which lab will analyze the samples, and is it accredited?
6. What is the standard for a pass, and who decides?
7. What happens if it fails, and who pays for the re-clean?
8. Will the report include photographs and readings I can keep?

Frequently asked questions

Sources

• U.S. EPA, Mold Remediation in Schools and Commercial Buildings, Chapter 3 (How Do You Know When You Have Finished Remediation/Cleanup?)
• NYC Department of Health and Mental Hygiene, Guidelines on Assessment and Remediation of Fungi in Indoor Environments (2008)
• OSHA, A Brief Guide to Mold in the Workplace (SHIB 03-10-10)
• CDC NIOSH, Mold, Testing, and Remediation
• CDC, About Mold and Your Health
• American Council for Accredited Certification, Mold Inspection Certification
• Oregon Legislature, ORS 105.464 (seller's property disclosure statement)

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