Mold Cleanup Methods That Don't Work

Evidence: Well supported (EPA and IICRC S520: physical removal is the goal; dead mold can still cause reactions).

Fogging fills a space with a fine mist, sometimes hydrogen peroxide, sometimes water or a product sold as a cure. A veteran inspector held that fogging, blasting or spraying into wall cavities cannot replace finding and removing growth, and she warned against firms that sell a gadget instead of a proper job. Her view of one special case changed over time. In earlier years she favored a final glycerin fog to settle the tiniest mold fragments at the end of a cleanup; later she saw it as a clash of competing science, after experts told her the physics did not hold up. She also warned never to fog with botanical or pesticide sanitizers, which can harm the lungs when breathed as a mist.

Evidence: Mixed or limited evidence.

Current guidance: IICRC S520 does not accept fogging as a mold removal method, nor as a stand-in for dealing with the source.

Ozone generators are sold to "kill" mold and odors. Clients of one veteran inspector sometimes noticed a musty smell fade for a while, but the growth stayed. Ozone reacts with other chemicals in a home to create new compounds, including formaldehyde. It can damage foam cushions, leather and fine paintings, and it irritates the lungs. Chemically sensitive people have reported new odors after ozone treatment that lingered and proved hard to clear.

Evidence: Well supported (EPA).

Current guidance: EPA warns that ozone can harm the lungs, that ozone at levels safe for people does little to clean indoor air, and that it does not reliably break down into harmless products.

The inspector this work builds on came to rank household bleach as a poor mold cleaner, no better than plain soap and water, and warned that breathing strong bleach could be a bigger health risk than the mold itself. In the early 2000s she had listed a bleach wipe in one cleanup protocol; she dropped it in later years.

Evidence: Well supported (EPA).

Current guidance: EPA says bleach and other biocides are generally not needed for routine mold cleanup. CDC allows bleach on hard surfaces at no more than 1 cup per gallon of water, with ventilation. Never mix bleach with ammonia or other cleaners; the fumes can be dangerous.

Painting directly over visible mold, with no cleanup first, hides the problem without fixing it. This is a contested area, and the inspector's own position deserves to be stated fairly. She held that in basements and crawlspaces, after the wood has been vacuumed and wiped and any water problem corrected, sealing every bit of exposed wood with paint or a sealing coating protects it from future growth, and that a light trace left beneath the coating is unlikely to return. She drew a clear line between that and painting over heavy visible growth. Some mold-injured advocates disagree and prefer to fix the water source and replace damaged materials outright.

Evidence: Mixed or limited evidence.

Current guidance: EPA says not to paint or caulk over moldy surfaces; clean and dry them first. IICRC S520 holds that coatings cannot stand in for removal, but may go onto surfaces once they are clean.

• Find and stop the water.
• Remove growth physically: a sealed HEPA vacuum, careful wiping, and removing porous materials that cannot be cleaned.
• Protect people and the rest of the house while the work is done.
• Check the result afterward.

This page is for education only. It is not medical, legal or engineering advice. The inspector whose work this builds on was an environmental consultant, not a physician. Talk with your doctor about health concerns, and use licensed professionals for electrical work and large mold jobs. Products, prices and labs mentioned reflect the years they were recorded and may have changed.

Source: the field work of environmental inspector May Dooley, MS, MA, CMC

Mold Testing & Remediation Guide →