Killing the mould solves the problem

Does it work?

Does not work

Refuted by two independent public authorities addressing different halves of it. It is the most consequential belief about mould, because it is what makes people buy another bottle rather than open a window, and neither source is obscure.

This is a verdict on whether the technique is effective. Whether it is safe on a particular surface is a separate question, answered below.

Where not to use it

Why it works

The implicit mechanism is that mould is an organism, organisms can be killed, and a dead organism is no longer a problem. The first two are true. The third is where it fails, and it fails twice over — an inactive colony remains physically present as allergenic material, and the substrate it grew into is unchanged. There is a further practical gap: a product applied to a surface reaches the surface, while growth on a porous material has penetrated it, so even complete kill at the surface leaves the interior population intact.

Background

This is not a technique but the belief that governs how techniques are chosen, and two authorities contradict it from different directions. The federal conservation guidance says it flatly: killing mould does not eliminate all health hazards, and inactive mould may cause allergic reactions in sensitive people. The dead colony is still there and still an exposure. The environmental regulator adds the other half: unless the moisture problem is corrected, growth returns, and porous materials that have been colonised may need to be discarded rather than cleaned. Between them, three of the four things a person wants from a mould treatment are left undone — the material is still colonised, the exposure persists, the conditions are unchanged. Only the appearance is fixed, and a bleach product fixes appearance particularly well because it destroys the pigment. The sources support a different order: correct the moisture, remove the growth physically, and where a porous material is penetrated, replace it.

Conditions

• Applies wherever a mould product is used as the whole treatment

What it does not do

• It addresses the appearance and leaves the colonised material, the exposure and the moisture untouched.
• On a porous surface a product reaches the face and not the penetration.
• It gives no signal of failure until regrowth, so the same treatment gets repeated indefinitely.

What to use instead

• Moisture control — The treatment for mould that is not a cleaning product. Every authority puts it first, and it is the only thing that stops the problem recurring.
• Dehumidifier — Not a cleaning tool at all, and the most effective single purchase against mould — because it treats the cause the spray bottle cannot reach.
• Bath sealant — The most common place a household meets mould that will not go away, because the growth is inside the bead rather than on it.
• Mould fungi — The organisms behind the marking. Around 1.5 million species, each with its own conditions — and killing them does not end the exposure they created.