When and How Should You Use Bleach to Kill Mold

While bleach can seem like an effective way to kill mold, it should not be used in every situation.

The EPA does not recommend using bleach “as a routine practice” to clean up mold. We also discussed this in our article “Does Bleach Kill Mold & When Is It Recommended?

The truth is that bleach is a relatively accessible and convenient way to get rid of household mold — if used properly under the right circumstances. In this article, we’ll define what the “right circumstances” means and how you can use bleach to kill mold.

Does Bleach Kill Mold?

Bleach is a mixture of sodium hypochlorite (NaOCl) and other chemicals that are effective at killing micro-organisms like mold by denaturing proteins, enzymes, and other cellular components.

A 2012 study by the University of Arizona showed that 5 minute of exposure to 2.4% bleach solution results in greater than a 99.9% reduction in mold.

Direct exposure is needed for bleach to kill mold, which means that surface mold on nonporous surfaces can be cleaned up with a diluted bleach solution. On the other hand, mold on porous materials like wood or drywall is harder to kill because the bleach solution can’t reach the mold growing underneath the surface.

There are two main reasons why bleach is not recommended as routine practice for mold cleanup:

  1. Improper handling of bleach can be dangerous to your health.
  2. In most cases, it is not possible or desirable to sterilize the affected area with bleach, according to the EPA. Scrubbing with water and detergent is usually sufficient to dislodge and remove mold.

The use of bleach does not eliminate mold spores in the air — which can regrow if moisture remains — and it also leaves behind dead mold on surfaces — which can still cause allergic reactions.

When to Use Bleach

Bleach can be used to effectively get rid of mold in certain cases, such as cleaning patches of mold growing under your sink or between your shower tiles, when used safely and under the right conditions:

  • The affected surfaces are hard and nonporous (e.g. tile, sinks, bathtubs, hard plastics, painted metal, glass). Do not use bleach to kill mold on porous surfaces like wood, drywall, granite, and carpeting.
  • The total mold growth covers less than 10 square feet. For more severe mold problems, contact a licensed mold remediation professional.
  • The moisture issue that caused the mold growth has been fixed and the area has been thoroughly dried.
  • Personal protective equipment is worn (e.g. gloves, goggles, and N-95 respirator).
  • The area being cleaned is well-ventilated.

How to Kill Mold with Bleach

Before starting with mold cleanup, make sure that the area has been fully dried and any moisture problems have already been repaired — otherwise the mold will regrow.

Avoid exposing yourself or others to moldy spores or debris throughout the cleanup process. Never mix chlorine bleach solutions with other cleaning products that contain ammonia — this may produce highly toxic fumes.

  1. Wear personal protective equipment, including gloves, goggles, and an N-95 respirator.
  2. Make sure the work area is well ventilated. Open doors and windows or use a fan to exhaust the air to the outdoors.
  3. Use a vacuum cleaner (preferably with a HEPA filter) to suck up loose surface mold and debris.
  4. Use a disposable rag to scrub the moldy surface with water and detergent, then discard the rag when you’re done.
  5. Mix 1 cup of bleach into 1 gallon of water. Do not add any other cleaners.
  6. Use a spray bottle to apply the diluted bleach solution. Don’t rinse it immediately — let the solution stand for at least 15 to 30 minutes to set in.
  7. Scrub the surface with a stiff brush and rinse with water, then allow the surface to air dry completely.

Other Tips for Mold Prevention and Cleanup

  • The key to preventing mold is controlling moisture. If an unexpected leak or flood occurs, wet items and surfaces must be thoroughly dried within 24 to 48 hours — otherwise, assume mold will grow.
  • Keep indoor humidity below 60 percent and vent appliances that produce moisture, such as stoves and dryers.
  • Improve ventilation and air flow in bathrooms by using fans or opening windows when showering.
  • Cover cold surfaces, such as cold water pipes, with insulation to prevent condensation.
  • Mold may be hidden in places such as behind drywall, underneath carpets, and in ceiling tiles. Investigate thoroughly if you notice or suspect signs of mold.

Need Help with Mold Cleanup in NYC?

Green Orchard Group is a team of NYS-licensed mold assessment and remediation experts. If you need help getting rid of mold in your home or building, give us a call at (212) 219-8261 or use our contact form to get a free quote!