Why Bleach Does Not Kill Mold. Surprised?

why bleach does not kill mold


1) The object to killing mold is to kill its “roots” (hyphal fragments). Mold remediation involves the need to penetrate and disinfect porous surfaces such as concrete, wood and other cellulose based building materials. Chlorine bleach should not be used in mold remediation as confirmed by OSHA’s Mold Remediation/ Clean up Methods guidelines. The use of bleach as a microbial disinfectant is best left to kitchen and bathroom countertops, tubs and shower glass, etc. (non-porous surfaces)

(2) Chlorine Bleach does kill bacteria and viruses. Mold is a fungi, NOT bacteria and NOT a virus. Bleach is not effective in killing mold on porous surfaces. Bleach itself is 99% water and water of course is the main contributor to microbial growth. Current situations using bleach to remediate mold regenerated mold at twice the CFU counts than were originally found before bleaching. Bleach is an old and outdated method used for cleaning up mold. It is the only product people have known for years. The spore strains now associated within indoor air quality issues are resistant to the methods our grandmothers employed.

(3) What potential mold ‘killing’ power chlorine bleach might have is diminished significantly as the bleach sits in warehouses, on grocery store shelves or inside your home or business. 50% loss in killing power happens in just the first 90 days inside an un-opened jug or container. Chlorine constantly escapes through the plastic walls of its containers.

(4) The ionic structure of bleach prevents the chlorine from penetrating into porous materials such as concrete, drywall and wood. It remains on the outside of the surface, whereas mold has roots growing deep inside the porous material. The 99% water that is in bleach does penetrate the porous surface and actually feeds the molds roots. This is why a few days to weeks later you will notice that the mold returns.

(5) Chlorine Bleach accelerates the deterioration of most materials and wears down the fibers of porous materials.

(6) Chlorine bleach is NOT registered with the EPA as a disinfectant to kill mold. You can verify this important fact for yourself when you are unable to find an EPA registration number on the label of ANY brand of chlorine bleach. ALL proper Biocides have to be registered with the EPA, and all must contain a registration number on the container.

(7) Chlorine bleach off gases for a period of time. Chlorine off gassing can be harmful to humans and animals. It has been known to cause pulmonary embolisms in low resistant and susceptible people.

(8) Chlorine bleach will evaporate within a short amount of time. If the area is not dry when the bleach evaporates, or moisture is still in the contaminated area, you could re-start the contamination process immediately and to a much greater degree.

If Not Bleach, What Can I use?

If you have an area of mold on a porous surface, you have two options.

1) Completely remove and replace the affected area.

2) Remediate by encapsulation. This is typically a two stage process in which the remediator will apply a proper EPA registered biocide spray (serum) to the affected area. The remediator will then apply a top coat sealant which will encapsulate the roots and prevent it from coming back.

Of course it is important to understand that it is never recommended to remediate until the issue that created it is resolved. Typically that involves locating the water source. Sometimes it can be caused from improper grading around your home, excessive vegetation around home, damaged gutters, downspouts discharging too close to the foundation walls, roof leaks etc. Once the moisture issue is remedied, then the process of mold remediation can take place.

Conclusion: Chlorine bleach, has been generally perceived to be an “accepted and answer-all” biocide to abate mold in the remediation processes for years. New studies have now proven that chlorine bleach is ineffective in killing mold. In fact, the Environmental Protection Agency (EPA) and the Occupational Health and Safety Administration (OSHA), have both changed their prior recommendations and do NOT recommend the use of chlorine bleach as a routine practice in remediation.