Black Toxic Mold

Does Bleach Kill Mold

This page discusses how to kill mold with:


The Mold Removal page also provides a step by step guide to the entire mold removal process.

The Mold on Clothes page has information about removing mold from clothes with bleach and other mold killing solutions.

Chlorine Bleach Information

Bleach is probably the most well known mold killer. Many commercial mold killing products contain bleach.

The active ingredient in chlorine bleach is sodium hypochlorite. Otherwise, bleach is mostly made up of water.

Bleach is cheap and you can easily buy it at the supermarket. Chlorine bleach is often called laundry bleach.

Does Bleach Kill Mold

Bleach kills bacteria and viruses and sanitizes the surfaces it's used on. Bleach also kills mold which it comes in contact with. Bleach neutralises the spores and allergens from mold as well.

Bleach will completely kill mold growing on non-porous surfaces like glass, tiles, bathtubs and counter tops. However bleach cannot completely kill mold growing in non-porous materials such as drywall and wood.

Bleach does not penetrate into these non-porous substances. Therefore only the mold growing above the surface is killed by the bleach.

How to Kill Mold With Bleach

  • Before you start, open the doors and windows to ventilate the area.

  • Bleach damages your skin so wear protective gloves. You might also want to wear eye protection too.

  • Next, mix the bleach with water. The ratio should be one cup of bleach per gallon of water. This is about a one part bleach to ten parts water ratio. However, check the instructions on the bleach as well.

  • Apply the bleach to the moldy surface. You might want to use a spray bottle or a cloth or sponge. Bleach can slowly destroy sponges and cloths though.

Should You Use Bleach to Kill Mold?

The EPA does not recommend bleach for killing and removing mold. Bleach is a chemical. It is better to use natural mold killing products. Some good alternative mold killing products are borax and vinegar.

Bleach also loses its power with time. Even if bleach is not opened, in 90 days it loses 50% of its killing effectiveness.

Bleach is also corrosive. Bleach deteriorates materials and the fibres of porous substances. And the gas from bleach can damage your lungs. If bleach touches your skin it can also give you chemical burns.

There is also concern about whether bleach leaves dioxins. Dioxins are highly toxic and carcinogenic. Dioxins are also teratogenic. Animal tests have shown dioxins can cause birth defects.

Bleach can create dioxins in processes such as bleaching of wood pulp. However, studies have found that bleach cannot form dioxins when it's just used for household cleaning. The materials which are needed for bleach to form dioxins are not usually found in a household setting.

Bleach is ineffective at killing mold on many materials, such as carpet and upholstery. Bleach won't kill mold on dirty, metallic or porous substances.

Why Bleach Does Not Kill Mold on Porous Material

You shouldn't use bleach to kill mold on porous materials. Because of its ionic structure, bleach cannot soak into these materials. The chlorine stays above the surface, while the water is absorbed in.

Therefore bleach only kills the mold on the surface. The mold's roots are left alive in porous substances like wood and drywall. This means that the mold can soon grow back. This can leave you in a cycle of continually bleaching moldy substances.

Oxygen Bleach to Kill Mold

An alternative to chlorine bleach is oxygen bleach. Oxygen bleach also kills mold. You can use it to clean mold from surfaces and clothes.

Oxygen bleach cleans stains and kills bacteria. It will sanitize, disinfect and deodorize whatever you use it on.

Oxygen bleach is another name for sodium percarbonate. It comes in a powder which you can mix with water.

The oxygen bleach powder dissolves in water. It then breaks down into hydrogen peroxide (which breaks down to water and oxygen) and sodium carbonate (also called sodium ash). These by-products are non-toxic and environmentally safe.

Many cleaning products contain oxygen bleach (eg Oxiclean). You can buy oxygen bleach from the supermarket. Usually oxygen bleach is cheap, costing just a few dollars.

Advantages of Oxygen Bleach

Oxygen bleach has many advantages. It also has many differences compared to chlorine bleach.

Oxygen bleach deodorizes and kills mold and bacteria. Unlike chlorine bleach though, oxygen bleach is environmentally friendly.

Oxygen bleach contains no phosphorous or nitrogen. Its ingredients are natural and biodegradable.

Unlike chlorine bleach, oxygen bleach won't fade or deteriorate clothes. You can also use oxygen bleach with hot or cold water.

Gas from chlorine bleach is bad for you, but oxygen bleach does not create fumes. Oxygen bleach does not fade surfaces like wood either.

Oxygen bleach can be used with other household cleaners and detergents. Chlorine bleach, however, is toxic if you mix it with vinegar or ammonia.

Both chlorine bleach and oxygen bleach can be bought cheaply from the supermarket.

Disadvantages of Oxygen Bleach

Oxygen bleach products are usually a little bit more expensive than chlorine bleach products. Chlorine bleach also works faster than oxygen bleach.

Oxygen bleach loses its killing power much faster than chlorine bleach too. You should use oxygen bleach within the time stated on the product for best results.

How to Kill Mold With Oxygen Bleach

  • The general directions should be on the oxygen bleach you buy. You can follow these to kill and remove mold.

  • Usually you begin by adding the oxygen bleach powder to water. Use warm or hot water, as this will dissolve the oxygen bleach better.

  • The ratio of bleach to water is usually between half a cup and one cup, per gallon of water. However, check for the ratio the directions on the oxygen bleach recommend.

  • You can add the oxygen bleach and water solution to a sprayer or squirt bottle to appply it to the moldy surface. If you prefer, you can put the oxygen bleach and water mixture in a bucket, and apply it with a cloth, sponge or scrubbing brush.

  • After you have applied the solution to the mold, let it sit for about 15 minutes.

  • Then thoroughly rinse and wipe the area with water.

  • You can also make a paste if you prefer. Add just enough water to the oxygen bleach powder to make it into a paste.

  • After you mix oxygen bleach with water, the solution will be active for about 5 or 6 hours. Dispose of it after this. It is fine to pour the solution down the drain, as oxygen bleach deodorizes drains.