Stories are hitting the media saying bleach doesn’t work in mold cleanup and prevention. An LSU AgCenter expert says there are reasons for some of the confusion but that bleach is effective at killing mold.
"What people are hearing is both true and false," said Dr. Claudette Reichel, a housing specialist with the LSU AgCenter.
Bleach is convenient, inexpensive and appropriate as a sanitizer for hard, non-porous, non-metallic and color-fast items after they have been cleaned, but it has some limitations when cleaning flooded buildings, Reichel stressed.
"Bleach can kill mold," Reichel said. "But if the surface is dirty, the bleach can get ‘spent’ oxidizing the organics and not get a chance to penetrate the mold structure enough to kill it."
That’s one reason it’s important to clean first and then disinfect, Reichel said. It’s also important to use a solution that’s strong enough – generally 1/2 to 1 cup of bleach per gallon of water – and to leave it on long enough to work – about 30 minutes.
Residual mold spores should then be removed, since killing them does not eliminate their potential health effects or toxicity – if they produced toxins, Reichel advised.
The housing specialist also explained that bleach has no residual effect. In essence, it’s gone in minutes and will not remain to inhibit the growth of new mold colonies on damp materials.
"That’s why it’s so important to speed dry after disinfecting, if possible," Reichel said.
To speed dry wet materials, Reichel suggested closing windows and running air conditioning or heat, running fans and using a dehumidifier.
"If that’s not possible because you don’t have power, some sort of treatment that inhibits mold or makes the material inhospitable can help," she said. Borate treatments, with the added benefits of termite resistance, may help, along with other products that are on the market, she said.
"In addition, bleach should not be used on metals because it is corrosive," Reichel said. "It’s important not to allow bleach to contact wiring, and it should not be used in an air-conditioning or heating system."
Reichel said a fact sheet distributed by the Federal Emergency Management Agency says treatment with commercial mold removers eliminates visible evidence of mold growth on exposed surfaces and is recommended for restoring flood-damaged homes.
In addition, tests have found very little or no evidence of mold growth in the unexposed or hidden portions of the walls and that treating the unexposed portions of the walls for mold control does not appear warranted in most cases.
FEMA recommends spraying vertical surfaces using a pump-up garden sprayer with a commercial mildew remover.
For more information, including the new fact sheet "Mold Removal Guidelines for Your Flooded Home," visit the LSU AgCenter’s website.