Mold- to Bleach or not to Bleach?

Mold and mildew refer to tiny microscopic fungi that exist nearly everywhere. Fungi do not require light to survive, since they do not perform photosynthesis. Rather, they reproduce through microscopic spores.

Mold and mildew often appear as brown, green or black spots, and usually cause a musty smell. Mold and mildew typically grow in damp locations, like basements and showers. Some common indoor molds include Alternaria, Cladosporium, Aspergillus and Penicillium.

Mold Health Effects

Fungus causes respiratory symptoms in some people, including coughing and wheezing. Other symptoms of exposure can include eye or skin irritation. People with asthma may experience an asthma attack when exposed to fungus. People who are sensitive to mold should avoid areas that commonly have high levels of mold, including saunas, antique shops, flower shops and greenhouses.

Fungus test kits are available, but the Center for Disease Control (CDC) does not recommend testing fungus in the home or workplace; any kind of mold or mildew should be eliminated.

How to Clean Moldy Areas

You can clean small mold problems yourself. In many cases bleach can be a perfectly viable method to do so, but use it with caution and understand that it is not effective for all surfaces.

When you decide to use bleach, get the diluted bleach solution of one part bleach to 10 parts water. You can add a few drops of detergent if you wish to get rid of any grime as well. Ensure the detergent does not contain ammonia as combined with bleach, ammonia can cause deadly toxic fumes. Use caution as bleach can be corrosive. If you have concerns about using bleach, try a solution of detergent and water. It is vital you protect yourself by wearing rubber gloves, protective eyewear, and a disposable dust mask.

Ventilate the area as much as possible as bleach fumes can be irritating. Apply the bleach mixture, scrub the entire area, and let it sit for 10-15 minutes. Rinse with clean water and dry the area thoroughly; this is essential if you want to reduce the risk of mold returning. Use a fan to get air circulating in the area. Get rid of all sponges or rags you used to clean the mold and immediately wash the clothes you wore while cleaning.

Cleaning Specific Surfaces

Clean Wood: If the wood is dry, vacuum the mold from the surface of the wood. If the wood is damp apply a solution of mild detergent and water (no bleach) and clean with a damp rag. If the mold remains, sand the wood, vacuuming as you go. If the mold is throughout the piece, it should be discarded.

Clean Paint: Never paint over a moldy area as this will not stop the mold from growing. Clean as suggested above and ensure the area dries quickly.

Clean Vinyl or Linoleum Floors: Apply the bleach solution described above, scrub, and rinse with clean water. Dry the area thoroughly, discarding the cleaning materials used on the floor.

Clean Concrete: Vacuum the affected area and scrub it with the bleach and detergent solution. Do not leave the area wet for long.

Clean Drywall: It is best to replace the affected piece(s) of drywall to prevent the return of mold. Before putting on the new drywall, ensure the areas behind and around it are not contaminated by mold and there are no wet areas that need to be fixed. Small moldy patches on drywall can be vacuumed and then cleaned with the bleach and detergent solution, making sure to not make the area even moister.

Clean Clothes: Moldy clothes should be dry cleaned or washed with laundry detergent and a cup of bleach. Before adding the bleach ensure the detergent does not contain ammonia. Repeat if necessary.

Clean Carpets: Moldy carpets, rugs, and underlay should be replaced. It may be frustrating to toss out what seems like perfectly good carpet but there is no way to get 100% of the mold out of infected carpets.

Keep in mind that it is necessary to fix the underlying cause of moisture that caused the mold growth as well as to remove the current mold. Regularly recheck prior moldy areas for regrowth.

Should You Reach for the Bleach for Mold Remediation?

Bleach is commonly believed to be an effective fungicide (mold-killer). In one situation, it may be effective: on hard, non-porous surfaces such as a countertop or shower stall. On porous surfaces it may not be as effective – in fact, it can actually feed the mold and make the problem worse. This is counterintuitive – it goes against the common thought that bleach kills germs. How can bleach feed the mold, when it is supposed to kill it? It has to do with the composition of bleach and the structure of mold.

Chlorine bleach is mostly water. The water in the bleach carries the active chemical ingredient known as chlorine (sodium hypochlorite). Several sources, including bleach-mold-myth, say that the chlorine in bleach remains on the surface of the wood and does not soak down into the wood.

Mold grows in colonies, sending out branches as it grows. Killing one part of the mold will not kill the mold. Instead, the mold comes back. If it has been fed by using bleach or some other household cleaner, it comes back stronger.

How Chlorine Bleach Makes Mold Worse

The chlorine does not soak into the porous materials (wood, wallboard, ceiling tiles), but the water in the bleach does. The bleach might kill the mold that is on the surface of the wood, but because the chlorine cannot penetrate the wood, it will not kill the mold structures that are underneath the surface.

The water soaks down into the porous material to where the roots of the mold are. Moisture is one of the few requirements mold has. Now that even more of the wood has become moist, thanks to the water in the bleach, the mold can spread into that area and continue its feast.

Using bleach on mold on porous surfaces is like cutting off some of the leaves of a plant while feeding the roots, and thinking that the plant has been killed. The plant will just grow more leaves, and the plant will be stronger because it has been fed.

The Clorox ® Company, OSHA, and the EPA all have determined that bleach should not be used in mold remediation. Bleach is ineffective and unsafe for cleaning up mold or killing mold. It appears to kill the mold, but just the surface mold is affected – the hidden mold underneath the surface is alive and well – now it’s doing even better. The mold says, “Thanks for the food! See you in a few days!” and the surface mold will soon be back.

Then the mold grows back to the surface, often there will often be even more of it. Bleach seems to help, but it makes it worse. There are ways to get rid of this unwanted houseguest, but bleach is not one of them.

Prevent Mold From Growing in Your Home

It is much easier to stop mold from growing in your home than to get rid of it once it is firmly entrenched in your walls and belongings. So the key thing is prevention! If you would like your house to remain mold free use the following tips-

  • Do not put carpet in your bathroom or basement.
  • Mold loves soap film so regularly clean surfaces like shower curtains, tiles, grout, and other bathroom areas with a product certified to kill mold and mildew.
  • Clean your shower floor regularly.
  • Don’t over-water houseplants.
  • Store firewood outside.
  • Check into adding mold inhibitors into paint when you buy a new can.
  • Regularly inspect carpet on concrete floors as carpet can absorb moisture.
  • Use your exhaust fan when cooking.
  • Regularly check and repair the caulking and grout in bathtubs and showers.
  • Ventilate whenever possible. If you home has a ventilation fan, use it.
  • Keep doors and windows open whenever possible.
  • Regularly clean ducts in your home’s heating and cooling systems. Remove and replace any insulation around air ducts that get wet; they cannot be adequately cleaned.
  • Vacuum all areas of your home often, preferably with a vacuum with a HEPA filter. This includes furniture and drapes as well as carpets.
  • Keep other surfaces clean with a product designed to kill household mold.
  • Cut the clutter in your house. This will improve air circulation and decrease the areas where mold can thrive.
  • Regularly clean your furnace filter. Replace it before it is completely clogged.
  • Check your roof for places water can enter and keep your eaves troughs clean. Do this often.
  • Make sure the grade of your lawn slopes away from to your home to keep water from pooling beside your home’s walls.
  • Routinely clean your home with a product designed to kill mold.

Control Humidity

  • The key factor in keeping mold from growing in your home is to control the level of humidity. Mold cannot grow without moisture.
  • Fix leaks immediately.
  • When showering turn on your exhaust fan and, if possible, open a window.
  • Vent moisture sources to the outside (dryer, dishwasher, bathroom fans, stove exhaust fan, etc.). Ensure they are not being vented into your home.
  • Use fans to circulate air.
  • Use a dehumidifier if your home’s humidity level is out of control. Close the windows when the dehumidifier is in use.
  • Turn your humidifier down if you have moisture collecting on your windows.

Indoor Humidity Levels

According to The American Society of Heating, Refrigerating and Air Conditioning Engineers, the following indoor humidity levels should be in place in your home in relation to the outdoor temperature.

  • +20 F. – 35%
  • +10 F. – 30%
  • 0 F. – 25%
  • -10 F. – 20%
  • -20 F. – 15%

A humidity level above 45% provides ideal conditions for mold growth and should be avoided.

To test the moisture level in your home you should  consider buying a hygrometer. They start at around $15 and can be found at most home improvement stores and you can easily fin them online.