This is a question that we get a lot of calls about, and that is “does bleach kill mold?” This is a subject that unfortunately has several answers. However, I’ll do my best at addressing when and where bleach can be used and when you should not.


Black mold or any mold remediation project should really be looked at on a case by case basis, truth is that no matter how long a professional mold technician has been on the field, no two projects will ever be the same. That being said let’s assume that we are talking about a relatively small area that’s been affected by surface mold growth. If the area that’s been affected is a nonporous surface like glass, tile, porcelain or any surface similar to that then bleach is a pretty good option and can get the job done from a sanitization standpoint.

But what if what has mold damaged is building material? Such things as drywall, baseboards, cabinets, framing and other porous material. Will bleach kill the pesty microbial growth? Here is where things start to get interesting! One could argue that yes, of course, it’s going to kill the mold, I mean if it kills it on tile why wouldn’t it kill it if it’s on my walls? And that’s a valid question. It all boils down to understanding the material looking to be treated and what makes up bleach.

Bleach, for the most part, is water. The disinfecting property we associate with bleach comes primarily from its active ingredient sodium hypochlorite. And yes, there are different types of bleach with different main active ingredients but for the purposes of this discussion, this is a good baseline. If you really want to geek out on bleach and its ingredients alongside other info check out Wikipedia post. Sodium hypochlorite only accounts for about 3%. Meaning that the rest is essentially water.

Water & elevated humidity is the main cause of mold growth. Also, the viscosity or thickness of the active ingredient is such that in most cases it can’t penetrate deep into building material. Water, however, can saturate building material like drywall or wood framing.

Imagine the act of shaving. If done right the razor blade seems to remove any trace of hair ever having been there. However, if you look closely with a magnifying glass you might see the pore and perhaps even the hair you thought was shaved off and gone. The same thing happens when cleaning building material with bleach. On the surface, the mold will be removed and to the naked eye, it looks like all is well. But if you look closer you’ll see that the roots or the hyphae is still present deep in the building material. What might have happened, however, is that the water content from the bleach may have increased the overall humidity and moisture content of the material?

By having building material with increased moisture mold has the ability to continue to grow. So does bleach kill mold and have the ability to sanitize? Sure, depending on the material.

Ideally, if there is significant microbial growth like mold on building material the best bet is to remove the material when possible. Then apply an approved nontoxic antimicrobial solution that has the ability to penetrate deep into building material like wood framing etc.

If dealing with a large area that needs to be remediated you may want to call a professional Mold Remediation company to properly handle the situation. But if you are a DIY’er then here are a few, probably oversimplified steps that you can take:

1) Set up containment or some kind of barrier to prevent cross-contamination
2) Make sure that you are wearing protective equipment, especially a good mask.
3) Get HEPA Air Scrubbers Installed in the work area, this will help in picking up lose airborne
mold
spores when removing affected material
4) Remove the mold affected material & bag it up as soon as possible. Make Sure that you tie the
bags
inside the work area
5) Apply an antimicrobial solution to the affected area.
6) HEPA Vaccum the affected area with as much detail as possible
7) If the area that was treated, like a wall cavity has wood framing and has some staining, feel
free to use antifungal paint like Killz to cover the area. Make sure to use a thick and even
coat
8) If available, for the work area with the antimicrobial solution or wipe down all the hard surfaces
with the solution including floors, walls, doors, and any furniture.
9) Before removing the trash bags with the affected material from the room, HEPA Vaccum the bags for good measure. The last thing you would want is contaminating other areas of the home
with mold after going through so much work.
10) If possible, let the air scrubber or scrubbers run for as long as you can. 48 hrs is a good rule of thumb here.

If you want to make sure that the project area is ok and mold levels are within acceptable ranges, contact a Mold Assessor and have them run an air sample.

Now it’s worth mentioning here that these 10 steps are an overly simplified guide or steps. Professional Mold Removal & Remediation takes many more factors into account like the air handling unit cleaning, duct cleaning, dehumidifiers and technology to use to effectively remove and kill mold from the home.

When possible, consult with a Licenced and/or Certifed Mold Profesional to walk you through the prosses.

I hope this helps clarify the question of the ages, Does Bleach Kill Mold?

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