Why Bleach Doesn't Fix Mould
Last updated
Bleach can make mould look like it’s gone, but it doesn’t remove it. Alberta Health Services’ fungal air testing protocol says treatment with only a biocide or disinfectant, such as bleach, is not acceptable remediation. Contaminated materials have to be removed, surfaces cleaned, and the result checked with clearance testing.
What the AHS protocol says
AHS sets out the standard for mould-contaminated buildings:
- Biocide-only treatment, like bleach, is not acceptable.
- Contaminated materials must be removed.
- Surfaces must be cleaned.
- Clearance testing follows to confirm it worked.
That’s the bar AHS uses when it issues orders on mouldy rental housing.
Why spraying isn’t enough
Mould grows into porous materials. Drywall paper, wood, insulation, carpet and ceiling tiles are absorbent. Mould grows into them, not just on top. A spray treats the surface. What’s inside stays.
Lighter isn’t gone. Bleach is good at removing colour. A stain that’s lighter can still be mould.
The moisture is still there. Mould grows where there are leaks, high humidity or condensation. Spraying doesn’t fix any of those, so it grows back.
Dead mould still matters. Even if a spray kills it, the mould material is still there. That’s why the protocol calls for removal and cleaning, not just treatment.
What works instead
- Find and fix the moisture source.
- Contain the area so spores don’t spread when materials are disturbed.
- Remove contaminated porous materials, like drywall, insulation and carpet.
- Clean the remaining surfaces, including HEPA vacuuming.
- Clearance test to confirm.
For small surface spots on hard, non-porous surfaces like tile or glass, soap and water and a good scrub is fine. See can I clean mould myself?
In older homes
Removing drywall, flooring or insulation in older Edmonton homes can disturb asbestos. If it’s suspected, licensed abatement professionals test and remove it before mould work. Our crews don’t do asbestos abatement.
Need it done properly?
See black mould removal and basement mould, or book an inspection.