More Information about Mold


Do not use Chlorine bleach to kill mold or disinfect moldy areas. It is not an effective or long lasting killer of mold and mold spores. Bleach is good only for changing the color of the mold and watering the roots 
of the mold.

Chlorine Bleach is Ineffective in Killing Mold for These Reasons:

(1) The object to killing mold is to kill its “roots”. Mold remediation involves the need to disinfect 
External link opens in new tab or windowwood and wood-based building materials, all of which are porous materials. Thus, chlorine bleach should not be used in mold remediation as confirmed by OSHA’s Mold Remediation/ Clean Up Methods guidelines. The use of bleach as a mold disinfectant is best left to kitchen and bathroom countertops, tubs and shower glass, etc.

(2) Chlorine Bleach does kill bacteria and viruses, but has not been proven effective in killing molds on non-porous surfaces. Bleach itself is 99% water. Water is one of the main contributors of the growth of harmful bacteria and mold. Current situations using bleach re-grew and regenerated mold and bacteria twice the CFU counts than were originally found before bleaching, within a short period of time. Bleach is an old method used for some bacteria and mold. It is the only product people have known for years. The strains now associated within Indoor Air quality issues are resistant to the methods our grandmothers employed to clean-up mold.

(3) What potential mold 'killing' power chlorine bleach might have, is diminished significantly as the bleach sits in warehouses, on grocery store shelves or inside your home or business 50% loss in killing power in just the first 90 days inside a never opened jug or container. Chlorine constantly escapes through the plastic walls of its containers.

(4) The ionic structure of bleach prevents Chlorine from penetrating into porous materials such as 
drywall and wood---it just stays on the outside surface, whereas mold has enzyme roots growing inside the porous construction materials---however, the water content penetrates and actually feeds the mold---this is why a few days later you will notice darker, more concentrated mold growing (faster) on the bleached area.

(5) Chlorine Bleach accelerates the deterioration of materials and wears down the fibers of 
porous materials.

(6) Chlorine Bleach is not registered with the EPA as a disinfectant to kill mold. You can verify this important fact for yourself when you are unable to find an EPA registration number for killing mold on the label of any brand of chlorine bleach.

(7) Chlorine bleach off gases for a period of time. Chlorine off gassing can be harmful to humans and animals. It has been known to cause pulmonary embolisms in low resistant and susceptible people.

(8) Chlorine bleach will evaporate within a short period of time. If the area is not dry when the bleach evaporates or moisture is still in the contaminated area (humidity, outside air dampness), then you could re-start the contamination process immediately and to a greater degree.

(9) Chlorine is a key component of dioxin. One of the earliest findings of dioxin's toxicity in animals was that it caused birth defects in mice at very low levels. This finding led to dioxin being characterized as "one of the most potent teratogenic environmental agents". The first evidence that dioxin causes cancer came from several animal studies completed in the late 1970's. The most important of these, published in 1978 by a team of scientists from Dow Chemical Company, led by Richard Kociba, found liver cancer in rats exposed to very low levels of dioxin. This study helped establish dioxin as one of the most potent animal carcinogens ever tested and, together with the finding of birth defects in mice, led to the general statement that dioxin is the "most toxic synthetic chemical known to man." Find out more about dioxin, 
by clicking External link opens in new tab or windowhere.

If Not Bleach, What Can I Use?

Chlorine Bleach and Mold Clean Up (Let's Set the Record Straight!)

(reprinted with permission from our friends at External link opens in new tab or windowSpore°Tech Mold Investigations, LLC)

The Myth

A myth exists concerning the use and “effectiveness” of chlorine bleach (sodium hypochorite) in the remediation of a mold problem. Mold remediation involves the removal and or clean up and restoration of mold 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 mold in the remediation processes. Well-intentioned recommendations of the Environmental Protection Agency (EPA) and other federal, state and local agencies are perpetuating that belief. And 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 mold remediation.

Does Bleach Really Kill Mold?

Will chlorine bleach kill mold 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 Spore°Tech Mold Investigations, LLC 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 molds and fungi, the company did not say. The words “hard, non-porous” surfaces” present the caveat. Mold 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 mold remediation as confirmed by OSHA’s Mold Remediation/ Clean Up Methods guidelines. The use of bleach as a mold disinfectant is best left to kitchen and bathroom countertops, tubs and shower glass, etc.

Why Chlorine Bleach is NOT Recommended for Mold 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 mold. The object to killing mold is to kill its “roots”. Reputable mold remediation contractors use appropriate products that effectively disinfect salvageable mold infected wood products. Beware of any mold inspector or mold remediation company that recommends or uses chlorine bleach for mold clean up on wood-based building materials.

Chlorine Bleach Is Active Ingredient in New Mold & Mildew Products

The appearance of new mold and mildew household products on store shelves is on the rise. Most are dilute solutions of laundry bleach. The labels on these mold 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 mold 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 mold 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 mold 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 mold, 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 mold and mildew products — keep in mind that the use of chlorine bleach is not for use on mold infected wood products including wall board, ceiling tiles, wall studs, fabric, paper products, etc.


Laundry bleach is not an effective mold killing agent for External link opens in new tab or windowwood-based building materials and NOT EFFECTIVE in the mold remediation process. OSHA is the first federal agency to announce a departure from the use of chlorine bleach in mold remediation. In time, other federal agencies are expected to 
follow OSHA’s lead.  The public should be aware, however, that a chlorine bleach solution is an 
effective sanitizing product that kills mold on hard surfaces and neutralizes indoor mold allergens 
that trigger allergies.

Using bleach can cause serious health problems. The fumes are very caustic and great care must be taken not to breathe it in too much. It is also very damaging to clothing and carpeting, the human body and the environment.

The most effective method to get rid of visible mold is by removing the affected area.

NOTE: MoldAcrossAmerica does not recommend the use of ozone to address mold or any other indoor air problems. For more information, visit External link opens in new tab or windowour website.

What does the EPA Have to Say about Using Bleach to Kill Mold?

"The Use of Chlorine bleach is not recommended as a routine practice during mold cleanup." (from the website.)

Chlorine Bleach is not a registered EPA mold killing product.

Does Bleach Kill Mold?

According to the EPA – “Biocides (like chlorine bleach) are toxic to humans as well as mold!"

The Minnesota Department of Health cautions “Bleach alone is not an effective way to combat mold. It won’t reliably kill mold, especially if organic contamination (dirt, dust, mold growth, etc.) has not been cleaned away first. Bleach consists mostly of water, so it can actually provide some of the moisture needed for the growth of mold. And finally, bear in mind that bleach treatment doesn’t actually remove mold spores or particles.”

University Study Discovers

Bleach is ineffective at killing mold on wood and other porous surfaces.

"While bleach is often recommended for remediation of surface mold on wood and other porous surfaces, our study results illustrate that the treatment does not eliminate the surface microflora," The research study was conducted by Professor Jeffrey Morrell, Dept. of Wood Science, Oregon State University, as assisted by Adam Taylor and Camille Freitag, as published in Forest Products Journal, 54:4, 2004.


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