Hugh Cairns: Bleach vs Mold

Bleach is not effective on porous construction materials like wood or drywall because it can’t penetrate deep enough into the material to kill. Photo: Contributed – (Photo: Hugh Cairns)

Common bleach is cheap and readily available at our local supermarkets. When it comes to killing mold most consumers reach for bleach first. Household bleach is mostly made up of water with sodium hypochlorite added as the active ingredient. Sodium hypochlorite is used in water purification, surface purification, bleaching, and odor removal. Bleach and water solutions have been used for killing mould as long as most of us can remember, most likely because it’s cheap and the appearance of instant results.

Sure, bleach is probably the most well-known mold killer, but it might not do the job that you are expecting it to do

Bleach doesn’t kill mold on porous surfaces

While chlorine bleach may be effective in certain applications it will not rid of mold on porous surfaces. Bleach only reliably works on hard, non-porous surfaces to kill mold. Mold often sends root like growth into anything that is remotely porous to survive.

Surface rigidity thwarts bleach from fully penetrating porous surfaces, resulting in a superficial surface mould kill only. Because the roots survive and the mold id not killed of entirely, soon it will grow again to suit the conditions that were conducive to its growth in the first place.

Bleach is not effective on porous construction materials like wood or drywall because it can’t penetrate deep enough into the material to kill. Surprisingly, using bleach on wood and drywall can have the opposite effect that was desired. The active ingredient sodium hypochlorite evaporates with contact with air while the water components reach further into the material and can actually feed mold growth.

Water is one of the largest enemies of your home. Mold can grow in many places, but the common element is a moisture source. Condensation around windows, drywall and wood wall framing that gets wet periodically, underneath wet carpets and other area that stays wet because of flooding or leaks are great breeding grounds for mold.

Bleach loses its effectiveness over time

Chlorine bleach rapidly loses its effectiveness due to evaporation. Evaporation occurs on surfaces where it is applied, and through open containers. Interestingly, chlorine bleach can evaporate through the very plastic bottle walls that it is stored in. Bleach that is stored for extended periods has the potential to diminish its potency.

Chlorine bleach is toxic

The off gassing of chlorine bleach can be harmful to us and our pets. Chlorine bleach is known to generate by-products like dioxin, which is linked to cancer.