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Does Bleach Kill Mold?

The Effectiveness of Chlorine Bleach in Fighting Mold

When faced with mold, many home and business owners are directed to use chlorine bleach to kill and destroy the unsightly problem.  However, what many people don’t know is that bleach is actually very ineffective against fighting mold growth.  There are many reasons why chlorine bleach is not recommended for the clean up of mold.  Because of these reasons, even the Environmental Protection Agency (EPA) fails to register bleach as a disinfectant to kill mold.  Here are a few of the reasons behind the ineffectiveness of bleach:

  • Chlorine bleach is too diluted to kill mold permanently:  Bleach is simply too weak to kill the mold on most surfaces, especially porous surfaces.  The structure of bleach prevents it from penetrating porous materials such as wood and dry wall.  Because mold grows its roots deep into the surface of a material, the bleach can only kill what is on the surface, allowing the roots of the mold to grow back.  If mold is simply sitting on a hard surface, the bleach could help kill it, though it also depends on how much cleaning the surface will need, because bleach cannot penetrate through dirt to kill the mold.
  • Chlorine bleach cannot cut through a dirty surface:  Because bleach cannot clean dirt and only masks it by making it transparent, any soiled surfaces that need mold removal will first need to be thoroughly cleaned and rinsed before attempting to disinfect with the bleach.  This adds double the time to kill and remove the mold as compared to a product that could be applied to soiled surfaces.  In addition, organic material quickly deactivates the killing power in bleach.  This means that if a surface is not rinsed well enough, the bleach will become ineffective even though there is a clean surface.
  • What killing power chlorine bleach does have rapidly diminishes:  Besides the fact that contact with organic material will quickly deactivate its killing and disinfecting power, chlorine bleach also has a very short shelf life.  As the bleach sits on the grocery store shelf or in the cupboards in a home, the Chlorine ions escape continuously through the plastic.  It is reported that there is a 50% loss in killing power in an unopened container of bleach in just the first three months.  Imagine how much killing power that chlorine bleach will have six months after leaving the warehouse; not much left to kill the powerful mold.

Groups such as the EPA, the Wall Street Journal, Health Departments of various states, and even Clorox, the leading manufacturer of chlorine bleach, have all stated that bleach is very ineffective at cleaning, disinfecting and killing mold.  Given this fact, it is evident chlorine bleach is weak, a poor remover of dirt, and a product that will only mask the problem deep below the surface.  Chlorine bleach should not be the first choice for mold removal, even on hard, non-porous surfaces in homes and businesses.

Bleach is a very strong oxidizer, meaning it causes material to oxidize such as rust or turn green; and it removes galvanizing from metal sheeting such as HVAC ducts.

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Copper water line has oxidized and the green material is Copper oxide.  If the Copper oxide is cleaned off with very light sandpaper, very small imperfections will remain in the copper pipe wall.

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Bleach has desolated the galvanizing coating.  Over time the relative humidity in the basement will start to oxidize the raw sheet and rust will appear.

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The bleach has spotted the galvanizing coating.

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The nails are rusted from exposure to bleach.

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This joist was cleaned with Bleach.  The wood color is very light.

The gray color on the joist is mold that has developed after only 10 weeks since the cleaning.