About DampOrDust

Most people with a damp bedroom, a musty wardrobe or a stuffy flat go straight to buying an air purifier. Many of them have a moisture or ventilation problem that a purifier can't touch. Some have a dust or smoke problem that a dehumidifier can't touch. DampOrDust asks four questions and points you at the free things to check and try first, before any money is spent.

What it can't do

• It can't see your home. It works only from the answers you pick, so it can't find hidden water damage or rule anything out.
• It doesn't identify mould, diagnose health problems, or tell you whether a home is safe to live in.
• It doesn't replace a building inspector, a licensed gasfitter, a doctor, or your local renting authority.

Thresholds we chose ourselves

We only suggest cleaning mould yourself when the patch is smaller than a dinner plate and on a hard surface. That is deliberately stricter than public-health guidance (the US EPA suggests most people can handle up to about 10 square feet), because this tool can't see the patch.

Where the advice comes from

Each figure is checked against a public source before it is used, and figures with no source are left out. Sources include the US EPA, AHAM, Health Victoria, Energy Safe Victoria, the National Asthma Council Australia, Consumer Affairs Victoria and manufacturers' published specifications. Where no source gives a number, the advice uses something you can see instead, like "until the mirror clears".

How the site is paid for

At the moment it isn't. If it carries ads they will be labelled as ads and kept off the questions and results. We don't sell products or earn commissions, because the site's job is to tell you when not to buy one.