Click here to go back

Chlorine Bleach and Mould Clean Up (Let's Set the Record Straight!) The Myth

A myth exists concerning the use and "effectiveness" of Chlorine® bleach (sodium hypochlorite) in the remediation of a mould problem. Mould remediation involves the removal and or cleans up and restoration of mould contaminated building materials.

Opposing Views and Confusion

Chlorine bleach, commonly referred to as laundry bleach, is generally perceived to be an "accepted and answer-all" biocide to abate mould in the remediation processes. Well-intentioned recommendations of the Environmental Protection Agency (EPA) and other federal, state and local agencies are perpetuating that belief. Confusing the issue is one federal agency, the Occupational Health and Safety Administration (OSHA), taking an opposing point of view by NOT recommending the use of Chlorine® bleach as a routine practice in mould remediation.

Does Bleach Really Kill Mould?

Will Chlorine bleach kill mould or not-yes or no? The answer is yes, but with a caveat. That answer comes from The Clorox Company, Oakland CA, manufacturer and distributor of Ultra Clorox® Regular Bleach. The company's correspondence to MicrobeGuard stated that their Tech Center studies supported by independent laboratories show that "…3/4 cup of Clorox® liquid bleach per gallon of water will be effective on hard, non-porous surfaces against… Aspergillus Niger and Trichophyton mentagrophytes (Athlete's Foot Fungus)". Whether or not Chlorine® bleach kills other moulds and fungi, the company did not say. The words "hard, non-porous surfaces" present the caveat. Mould remediation involves the need to disinfect wood and wood-based building materials, all of which are porous materials. Thus, Chlorine® bleach should not be used in mould remediation as confirmed by OSHA's Mould Remediation/Clean-Up Methods guidelines. The use of bleach as a mould disinfectant is best left to kitchen and bathroom countertops, tubs and shower glass, etc.

Why Chlorine Bleach is NOT Recommended for Mould Remediation

Chlorine bleach (sodium hypochlorite) is corrosive and that fact is stated on the product label. Yet the properties of Chlorine® bleach prevent it from "soaking into" wood-based building materials to get at the deeply embedded mycilia (roots) of mould. The object to killing mould is to kill its "roots". Reputable mould remediation contractors use appropriate products that effectively disinfect salvageable mould infected wood products. Beware of any mould inspector or a Mould Remediation Company that recommends or uses Chlorine® bleach for mould clean up on wood-based building materials.

Chlorine Bleach Is Active Ingredient in New Mould & Mildew Products

The appearance of new mould and mildew household products on store shelves is on the rise. Most are dilute solutions of laundry bleach. The labels on these mould and mildew products state that they are for use on (again) hard, non-porous surfaces and not for wood-based materials. Instructions where not to apply the products are varied. A few examples where the branded products should not be applied include wood or painted surfaces, aluminum products, metal (including stainless steel), faucets, marble, natural stone, and, of course, carpeting, fabrics and paper. One commercial mould and mildew stain remover even specifically states it should not be applied to porcelain or metal without immediate rinsing with water and that the product isn't recommended for use on Formica® or vinyl.

Caveat Emptor!

Before purchasing a mould and mildew product, read and fully understand the advertised purpose of that product - and correctly follow the use instructions of a purchased product. The labeling claims on these new products can be confusing - some say their product is a mould and mildew remover while another says their product is a mildew stain remover and yet others make similar 'ambiguous' claims. Make double sure that the product satisfies your intended need on the surface to which it is to be applied. If your intention is to kill mould, make sure the product does exactly that and follow the directions for usage. Consumers may find that mixing their own diluted bleach solution will achieve the same results as any of the new mould and mildew products - keep in mind that the use of Chlorine® bleach is not for use on mould infected wood products including wall board, ceiling tiles, wall studs, fabric, paper products, etc.


Laundry bleach is not an effective mould killing agent for wood-based building materials and NOT EFFECTIVE in the mould remediation process. OSHA is the first federal agency to announce a departure from the use of Chlorine® bleach in mould remediation. In time, other federal agencies are expected to follow OSHA's lead. The public should be aware, however, that Chlorine® bleach solution IS an effective sanitizing product that kills mould on hard surfaces and neutralizes indoor mould allergens that trigger allergies.

Back to the top