For generations, people have believed that bleach kills mold. The truth is “Bleach only Bleaches Mold’s Color but Antimicrobials Kill Mold”. Bleach (sodium hypochlorite) is an old and misunderstood chemistry that has been used for many years to clean up mold in all kinds of applications. Many people boldly and confidently tell us that they have been using bleach products to remove molds for 30 years and are convinced that it is the best product to use. What is worse is that most will not listen to an argument against their tried and true mold killing product even if you are the professional with research backing up your statements. Most often coming from the maintenance supervisor at some multifamily housing community stating boldly, “it’s OK, I sprayed it with bleach and look it’s gone.” Which brings me us to our next point, why does bleach not kill mold if it is gone after being used? Bleach is effective against removing only mold stains because it is a strong oxidizer which removes the color of mold. Removing the color does not justify the opinion that bleach kills mold. Remember we use bleach in our laundry to bleach our clothes? It’s to bleach them white again and remove the stains…stain removal! When bleach is sprayed on nonporous surfaces the mold disappears for a short time only to reappear later. In an experiment done on roof shingles, the roof was cleaned using a mixture of diluted bleach. At first, it looked very clean only to reappear weeks later more prevalent than before. This is also the reason why those annoying mold spots keep reappearing in your shower or tub no matter how many times it is cleaned off.
The Clorox Company who manufacturers Ultra Clorox® has actually hired a third-party firm to conduct studies to determine its performance. The results of these lab reports conducted by Spore Tech Mold Investigators reveal the following “…liquid bleach mixed at 3/4 cup of Clorox per gallon of water will be effective against hard, non-porous surfaces against… Aspergillus niger and Trichophyton mentagrophytes (commonly known as Athlete’s Foot Fungus)”. These were the only two molds listed in the study and we have no other data related to its effectiveness of killing toxic molds like Stachibothris (commonly known as black mold). In addition, the study was conducted on a hard nonporous surface the known limitations of bleach. So to summarize, we have two molds out of hundreds that can be eliminated from bleach if the cleaning is done on a nonporous surface. No wonder professional mold contractors do not use or approve of the use of bleach in their remediation process as they mostly work with semi-porous surfaces. This makes common sense because mold needs porous materials to grow. Therefore bleach is arguably only useful in cleaning hard surfaces and is not sufficient for mold remediation. The properties of chlorine bleach inhibit it from penetrating into porous materials to effect and or kill the deeply embedded roots of the mold. Killing the roots of mold, the actual bacteria is really the goal of any quality mold remediation contractor. OSHA is actually the first federal agency to begin changing their recommended use of bleach for mold removal. It is only a matter of time for other federal, state and local public safety agencies also begin distancing themselves from chlorine bleach.
Every time I enter an environment where bleach has been used and I take that first breath of sodium hypochlorite I want to lose my lunch. This stuff is nasty! I can remember the pain in my burning lungs just writing about it. Every bottle of chlorine bleach has a hazard warning label for a reason, it is corrosive and toxic. As a restoration professional, I am continually exposed to all kinds of environments, chemicals & toxins. If I had to breathe in mold spores or bleach fumes I would rather breathe mold spores any day.
So know you know that the common statement “bleach kills mold” is untrue, what do you use? For the common homeowner who doesn’t have experience with mold, we say to keep it simple. If you are simply cleaning molds off a hard nonporous surface simply use a green disinfectant or simply dish soap mixed into a spray bottle. Dish soap will not kill the mold but it will loosen it so it can be wiped off the hard surface and absorbed onto the paper towel for disposal. You would actually do better to spray the towel first then wipe the surface collecting the mold on the towel. As a professional, we prefer to use a nontoxic enzyme mold cleaners or essential oil based disinfectants which do penetrate into porous materials for effective killing of the underlying bio-slime (mold roots) and thereby extracting it permanently. The EPA recommends for any molded area over 30 square feet contacting a mold specialist to prevent health ramifications from improper mold removal. Bleach is a very toxic chemical and can cause burning of the lungs and breathing passages if inhaled and even lead to severe poisoning.