Mold and Restoration: Answers From the Expert

March 10, 2003
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I am always fielding questions from hopeful restorers looking for quick and easy ways to deal with mold. It seems that everyone is looking for the magic bullet to solve all their problems with little or no effort and, certainly, at little or no cost.

Obviously, that’s not going to happen. However, I see some of the same questions popping up in e-mail and on industry forums all the time. This is one attempt to deal with some of those questions “once and for all.”

“Will ozone “kill” mold, including spores, and if so, at what level of concentration?”
Closed-chamber testing conducted by Research Triangle Institute indicates that ozone has little or no effect on mold on drywall or wood. Ozone gas, in the concentrations that can be produced by normal generating equipment in typical water-damaged structures, is ineffective in killing or even controlling microbial growth on structural and contents materials. Closed-chamber testing in which Penicillium was exposed to 9 ppm of ozone at varying levels of humidity on a variety of building materials (wood, drywall, ceiling tiles) yielded no reduction in colony-forming units after 23 hours.

While I’m at it, let me point out that UV systems for structural mold remediation are no better.

“OK, so what about the use of biocides to prevent and stop mold growth and amplification?”
The American Conference of Governmental Industrial Hygienists in “Bioaerosols: Assessment and Control” specifies:
15.2 - Growth that has occurred in a surface layer of condensation on painted walls or non-porous surfaces (including wood) can usually be removed by (a) vacuuming using equipment with high-efficiency filters or direct air exhaust to the outdoors, (b) washing with a dilute solution of biocide and detergent, or (c) cleaning, thorough drying, and repainting…Porous materials that have sustained extensive microbial growth must often be removed.
15.4 Biocide Use - Remediators must carefully consider the necessity and advisability of applying biocides when cleaning microbially contaminated surfaces [see 16.2.3]. The goal of remediation programs should be removal of all microbial growth. This generally can be accomplished by physical removal of materials supporting active growth and thorough cleaning of non-porous materials. Therefore, application of a biocide would serve no purpose that could not be accomplished with a detergent or cleaning agent.
16.2.2 Biocides - Biocide use should not be considered if careful and controlled removal of contaminated material is sufficient to address a problem.
16.2.3 - Effective remediation of water-damaged or microbially contaminated buildings involves (a) the use of appropriate techniques to promote rapid drying, and (b) complete removal of contaminated materials rather than the application of biocides without these steps.
16.2.4 - Biocide application is not recommended in the restoration of water-damaged indoor environments except where they have suffered extensive sewage backup. Widespread pollution from raw sewage presents a significant health risk from a variety of infectious agents, and biocides may help to control and contain these agents during the restoration process (Berry et al., 1994; IICRC S500, 1995). That process includes the following steps: sewage extraction, application of biocide, removal of organic residuals, cleaning of all surfaces, and secondary application of biocide if deemed necessary. Sewage-contaminated porous materials must be discarded. Likewise, porous materials that, for any reason, remain wet for >24 hours should be discarded. The Institute of Inspection, Cleaning, and Restoration Certification (IICRC, Vancouver, WA) has published guidance for biocide spray application (IICRC S500, 1995).

The emphasis today is on thorough cleaning to create a healthier environment. Applying biocides must not be considered a substitute for detailed and meticulous cleaning of surfaces to achieve bioremediation. With this in mind, professional authors and instructors are recommending meticulous cleaning rather than applying biocides indiscriminately on clean-water-source losses. When mold is present, source removal, rather than biocide application, is the proper remediation strategy.

When does drywall or structural materials have to come out?”
This is one of those all-encompassing questions that is a little hard to pin down. I think the common sense response is that when materials show physical damage or significant mold growth and they are too delicate to restore with industry-accepted remediation procedures (HEPA vacuuming, detergent cleaning, sanding), they should be removed and replaced with new material of LKQ (Like Kind and Quality).

“What should be done when mold is discovered during basic water restoration loss mitigation services?”
Contain the area, stop work and discuss options with responsible parties who have the experience and expertise to provide further advice about additional restoration procedures.

“Does mold grow faster and produce more spores as the structure, contents and ambient air are being dried?”
During professional remediation, that depends on how thorough the remediation procedures have been and how well temperature is controlled. When existing vegetative mold “senses” that ambient conditions are going to be less than favorable, some species will produce a quantity of spores in order to ensure that the species is perpetuated and allowed to re-grow later during unfavorable conditions.

“If we set in dehumidifiers during loss mitigation when mold is present, how much airflow is too much?”
Any airflow is too much in some circumstances. Depending on the species of mold, simply walking by a contaminated surface can render large quantities of spores airborne in respirable air.

Typically, to prevent spread and further contamination, restoration procedures include, but aren’t necessarily limited to:

  • Contain the area
  • Create negative pressure using AFDs
  • Have an environmental consultant sample, evaluate and advise
  • HEPA vacuum all areas
  • Isolate, remove and properly dispose of heavily contaminated materials
  • HEPA vacuum exposed pockets
  • Dry using procedures outlined in IICRC S500

    “If mold is growing on drywall, is it ever acceptable to clean it off?”
    Complicated question. If there is any visible growth on painted drywall surfaces, a technician must consider what is growing on the opposite side. If there is minor growth, due to surface condensation or high ERH, the surface can be HEPA vacuumed and cleaned with an appropriate detergent. After thorough drying, sealing and repainting will cover residual stain. However, when optimum growth conditions are reintroduced, especially moisture or high humidity, and you can expect mold to re-grow on that surface.

    “Should antimicrobial paints be used as sealers on walls or structural materials like cleaned and sanded studs?”
    While antimicrobial paints don’t hurt, never should they be used as a substitute for proper mold remediation procedures. Under optimum growth conditions or when there is a significant bio-film on the paint, mold still can re-develop and cause problems. The key is clean and dry.

    “How do you ensure that no mold growth from inside walls will become airborne by passing through openings at electrical outlets, switch plates and wall plates along the subfloor or floor?”
    You can’t confine mold growth within walls. Convection currents and pressure imbalances, particularly as air in wall cavities expands and contracts with normal heating and cooling, causes exfiltration (movement of air from inside to outside). Proper inspecting and/or testing, followed by conservative remediation protocols, is the key to preventing the contamination of respirable air.

    “Should an industrial hygienist (IH, CIH) always be called to inspect every job before remediating?”
    Not every industrial hygienist (IH) or even certified IH (CIH) is qualified to do pre- or post-remediation mold sampling. The proper person to call is a qualified “environmental consultant” or “environmental assessment specialist.” If that qualified environmental consultant happens to be an IH or CIH, so much the better. Based on building history, current moisture readings and the length time materials are exposed to excessive moisture, odor, occupant symptoms, visible mold, anticipated litigation, and a variety of other indicators, sampling may or may not be required. When in doubt, err on the side of caution. One would really be sticking his neck out to list all the conditions in which pre-remediation sampling would or would not be recommended. This must be handled on a case-by-case basis.

    “Where can I become certified in mold remediation?”
    Currently, there are two trade associations and one certifying body involved with mold:

  • Indoor Air Quality Association (IAQA) offering Certified Microbial Remediator (CMR) Certification – Glenn Felman. Call (301) 231-8388.
  • American Indoor Air Quality Council (AmIAQC) offering Certified Microbial Remediation Supervisor (CMRS) – Charlie Wiles. Call (800) 942-0832.
  • Institute of Inspection, Cleaning and Restoration Certification (IICRC) offering Applied Microbial Remediation Technician (AMRT) leading to AMRS (Specialist) – Tom Hill, Executive Administrator. Call (360) 693-5675.

    And there ends our lesson for today.

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