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Does Bleach Kill Mold? No It Doesn’t

Mold, a resilient and tough organism that is not only unsightly but also brings a lot of havoc in the form of structural damage and potential health effects.

Mold spores are ubiquitous, but moisture can be a limiting factor for active mold growth.

A musty odor and multi-colored patches on surfaces can be its hallmark characteristics that indicate its presence.

Many different products have been marketed to help homeowners say goodbye to mold infestations.

Your over-the-counter bleach is one of them.

It can produce the intended results but only on non-porous surfaces such as metal and glass. Bleach is less effective on any porous materials such as wallboard, wood, and most furniture commonly found in your home.

Porous materials have open pores and air gaps that provide a perfect breeding ground for mold spores. This characteristic of porous materials renders the use of bleach ineffective in most cases.

Porous items such as sponges, drywall, and furniture would provide a habitat for molds to grow deep beneath the surface.

No matter how often you clean the surface of the material, molds will continue to regrow unless the moisture source is eliminated.  

The EPA often discourages individuals from using bleach to remove mold growth. Especially on porous surfaces. However, bleach can be used to disinfect non-porous surfaces when professional judgment is used.

Limitations of Bleach When Combatting Mold Growth

Some significant concerns regarding using bleach to treat mold growth include:

  • Applying bleach to mold growth on porous materials may only remove the surface growth and render the mold colorless. In other words, bleaching the mold. The surface retains its original color giving a notion of “no worries.”  In fact, you have only cleaned the surface of the material.
  • Secondly, a bottle of bleach can already be devoid of most of its disinfecting capabilities if it remains on the shelf for long periods.  This will be useless for anyone attempting to use bleach to remove mold growth. The absence of the disinfecting power of the bleach can be more beneficial to aid mold growth than preventing it.  This is because bleach can contain more than 90% water.
  • Chlorine bleach, once exposed to air, can begin to lose its effectiveness. Also, chlorine bleach has a shelf life of about one year at most.  In some studies, sodium hypochlorite, the active chemical in bleach, begins to break down after six months.  The rate of sodium hypochlorite breakdown is increased when the bleach is not stored correctly and exposed to sunlight.
  • Chlorine bleach does not penetrate the materials to get to the roots of the mold growth.

Should you use bleach to clean mold from porous surfaces?

Bleach is not a recommended treatment method to remove mold growth from porous surfaces.

Here is Why?

This is mainly because the penetration of mold hyphae (root-like structures of the mold used to absorb nutrients) is deep in the material.

When this occurs, the application of bleach will only impact the mold growth on the surface of the material.

The reason mold is known as resilient is because it makes it through various harsh conditions and manages to survive.

Also, in the case of porous surfaces, to harness even more nutrients, mold hyphae will penetrate deep into the material on which it grows.

The application of bleach will cause the mold to change color and remove the surface growth, but the mold growth will resurface after a short period of time.

Treating moldy furniture and other porous materials with bleach will disintegrate the fibers and make them shattered and weakened.

In a nutshell, bleach, instead of eliminating the root cause of the problem, can sometimes make it worse and provide a false sense of security.

When in fact, after a couple days to a week, the mold growth will re-grow in the same area and spread even more.

Using Bleach to Get Rid of Mold on Porous Surfaces

To eliminate the risks of property damage and health effects associated with mold growth, the application of bleach on porous items has always been a bad move.

Bleach will temporarily hamper mold growth on the surface only. It’s the same as the idea of giving antibiotics to the virally infected person.

The person will get no beneficial health effects instead develop antibiotic resistance against already present antibiotics.

Here is a real example of what happens when you use bleach to clean mold from drywall. 

In this instance, we wanted to see what would happen if we sprayed bleach on some mold growth in a bathroom ceiling.

So, we identified an area with mold growth that was caused by high humidity and a bad exhaust fan.

We began by spraying bleach on the growth then used a sponge to scrub the area.

This was done until the growth was removed and the area was visibly clean. Then, we let the area sit for about a week without fixing the moisture problem.

What do you think happened after five days?

If you guessed that the ceiling was still clean because we applied bleach to the area, you would be wrong.  In fact, when we returned to look at the ceiling, this is what we found.

Look at the picture below.

Mold regrowth after cleaning the area with bleach.

This is what it looked like when it began to regrow.

If you look closely, you can see how the mold appears to regrow in the direction of how the sponge was wiped across the surface of the ceiling.

Pretty much, this is what happens if you fail to fix the moisture problem and just attempt to use bleach to remove mold growth. 

Dangers of Using Bleach for Mold Removal. 

Keep in mind, bleach is a biocide, meaning it’s a compound that kills living organisms. As a result, there are some health concerns when it comes to using chlorine bleach for regular mold cleanup.

  • Misusing bleach for any cleaning activity, not just mold removal, is always a bad idea and can cause serious injuries.
  • Prolonged exposure to this chemical can cause some serious health concerns.  Most of the health impacts are due to the reactive nature of bleach as it reacts with ammonia and a variety of acids releasing chlorine gas. This can lead to difficulty breathing and can cause excessive coughing. These effects can be worsened when using bleach in a confined space without proper ventilation. Doing so can cause chest pain and other respiratory complications.
  • It may lead to the irritation of the different body parts, including the mouth, eyes, and lungs. Individuals with respiratory illnesses such as asthma are at a greater risk.
  • Chlorine bleach can lead to skin damage as well. Its corrosive nature can cause severe burns and irritation, so proper protective covering and the well-aerated area are recommended while using it as a disinfectant.

Safer Alternatives

Luckily, there are some safer alternatives, such as baking soda and vinegar.

Also, there are several antimicrobial chemicals such as Benefect Decon and others that are plant-based and not as dangerous to your health.

Also, you can check the EPA for a list of chemicals that are registered as mold removal products. 

Note: Before using any chemical, always look up the Safety Data Sheet (SDS). This document contains essential safety information and precautions that must be taken when using the product.   A simple search online using the chemical name + “SDS” in the search bar should provide you with this information.

So, the next time you think using bleach to clean mold growth is a good idea, stop and think for a moment.

A long story short, instead of putting your health, environment, and belongings at risk, try reaching for alternatives if they are readily and easily available.


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