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Why Can't I Use Bleach to Kill Mold?

Wow, there is so much wrong with that question! Let’s break this question down into two parts: “kill” and “bleach”


As we are learning more about mold, we have learned that dead mold is more dangerous than live mold. Killing bleach will exacerbate the problem. Why? When mold is alive it breathes. When it dies and respirates its last breath, it releases toxins into the environment As dead mold dries out, it becomes less sticky and lighter, making it more easily airborne Dead mold persists and breaks down becoming hyphae fragments that are highly allergenic Toxic mold has chemicals. Chemicals are neither dead nor alive. These chemicals persist for years in the environment. They are very light and boyant and move on air flow. Rather than “kill” think “clean.” We want a home that is clean and free from elevated mold levels.


Bleach, long recommended for cleaning moldy surfaces, compares poorly with most other mold-eradication methods for the following reasons:

Sodium hypochlorite (NaCLO), the active ingredient in bleach, is produced by infusing sodium hydroxide with chlorine gas, a deadly gas that killed thousands of soldiers before gas warfare was outlawed.

Bottom line, bleach simply introduces more toxic chemicals, making indoor air quality hazardous. If bleach is accidentally mixed with an acid-containing cleaner (such as many toilet bowl cleaners, drain cleaners, and even lemon juice or vinegar), then deadly chlorine gas is released

Household bleach contains only 3%-6% sodium hypochlorite, because it is so caustic and dangerous. The remaining 94%-97% volume of household bleach is water. Using bleach or a bleach solution actually provides the three ingredients necessary for mold growth and allows for the quick rebound of mold growth, usually within 24 hours or less.

Bleach does kill mold on nonporous surfaces such as glass or stainless steel, but does not kills mold on porous surfaces (most of your home) and does nothing to the spores that are in the air. When the sodium hypochlorite dissipates, usually within a few hours of application, then mold growth can rebound. Application of liquid bleach to porous, mold-infested materials (such as wood, wallpaper, sheetrock, and the grout between bathroom tiles) will bleach the spore colonies and kill mold spores, but not all of the spores will be killed, and even dead spores can cause allergy symptoms.

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