How to use a mould test kit
Updated: October 2026
You already have a plate kit or a rapid strip. This page is how to sample, how long to wait, and how to throw the dish away without spreading what you grew. It does not rank products. Product choice sits on the [mould test buying guide](/hub/climate-measuring/mould-test/sub/mould-test-buying-guide). Housing letters sit on the [tenant page](/hub/climate-measuring/mould-test/sub/mould-test-for-tenants). The [main mould test comparison](/hub/climate-measuring/mould-test) is the model table if you are still unsure which box you opened. The leaflet in your box wins on times and temperatures. A blank dish is not a clearance for the room.
You already have a plate kit or a rapid strip. This page is how to sample, how long to wait, and how to throw the dish away without spreading what you grew. It does not rank products.
You already have a plate kit or a rapid strip. This page is how to sample, how long to wait, and how to throw the dish away without spreading what you grew. It does not rank products. Product choice sits on the mould test buying guide. Housing letters sit on the tenant page. The main mould test comparison is the model table if you are still unsure which box you opened. The leaflet in your box wins on times and temperatures. A blank dish is not a clearance for the room.
Our top picks
| Badge | Product | Method | How you sample | Then wait | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  iigala iigala mould test kit, 10 plates | Air or surface plate | One review: about an hour open | About 48 hours | 8.6 | about £24.99 | View offer |
| Best value |  anlab anlab mould test kit, 3 plates | Plate or swab | Use the time on the leaflet | About 48 hours claimed | 8.2 | about £13.59 | View offer |
| Alternative |  Healthful Home Healthful Home 5-minute mould test | Five-minute strip | Swab must touch the patch | About 5 minutes, control line required | 7.8 | about £39.97 | View offer |
On this page
Before you open the pack
Read the leaflet once, then check the expiry date. The gel should look intact, not cracked or already speckled. Label the base, not the lid, with the room and the date. If you are comparing two rooms, both samples need the same exposure on the same day.
NHS inform says not to spread dry mould into the air, and that people who are more vulnerable should keep away from that disturbance. Keep closed dishes out of reach. A fresh bleach wash can make the plate record the clean-up rather than the room. If the real question is whether a kit can stand in for an inspection, read the DIY or surveyor page.
Air plates
Close the windows and the internal doors. Switch off the cooker hood, the bathroom fan, and any desk fan for the sampling period unless your leaflet tells you to leave ventilation running. You want the air the room holds, not a draught from the landing.
Set the closed plate at about breathing height, off a radiator. The home kits behind this guide do not include an outdoor control. Use the exposure printed on your pack. An hour open, then bagged, is a figure that shows up in buyer notes. Stretching that hour breaks the chart that came with the box. When the timer ends, close the lid at once. Do not lift it again to check progress.
Swabs and the five-minute strip
A swab only works if it touches the patch you mean. Rotate the tip across visible mould, with light even pressure, and seat it straight into the tube. If the leaflet says the tip stays dry, leave it dry. Photograph the square. Bathroom wall on the label is useful. Mould problem is not.
A contact paddle, if your box has one, is a single press for the stated seconds. A second press samples a new patch and makes the chart meaningless. The five-minute strip runs on a different clock. The swab has to touch visible mould, and a control line must appear. A line still describes only that patch. Look along window reveals and behind furniture before you treat one strip as the whole room.
Blank dishes, furry dishes and disposal
Nothing grew. That can mean few viable particles landed, the gel was past its best, the room was too cold, or you read the plate too soon. Trust a stain you can see over a blank dish. Everything grew can mean the room shed a lot of viable particles, or that the lid was off too long. On a culture gel, mould often looks fuzzy, while bacteria often stay smaller and smoother. That is a reading hint, not an identification. Do not rename green as Penicillium or black as Stachybotrys at the kitchen table. Write down a count, no growth, or overgrown, then seal the lid. Used with the leaflet's hour and warmth, a mould test kit is a timed sample and a wait. A blank dish and a furry dish are hints about that sample, not a verdict on the house.
Common questions
What temperature should I use for every brand?
None. Brands do not share one clock. A plate claim often points at about 48 hours, while some UK sellers describe three to ten days at room temperature. One buyer complained that a leaflet asked for 84 to 100°F, about 29 to 38°C, which is impractical in a British home. That range is a review complaint, not a target. Put the plate where the leaflet's warmth is realistic, lid up and out of direct sun.
Is an empty plate on the first evening the result?
No. A peek on the first evening is almost always empty. Empty at that hour is not the result. Read the plate on the schedule in the leaflet, and do not lift the lid to check progress. Each opening adds whatever is in the air at that new moment.
What does no control line on a strip mean?
No control line means the strip is invalid. It does not mean the wall is clear, and it does not mean the test was negative. Reading long after the stated minutes, or adding extra drops to force a line, does not repair it. Discard that cassette and use another if the pack includes one.
Can I compost a furry dish or open it for a photo?
No. Seal the lid. Do not open a furry dish for a closer look or a sharper photo, and do not compost it. Bag the closed plate and put it in the household waste unless the leaflet tells you to post it back. Wash your hands. The incubated dish is concentrated growth.
When should I stop and bring someone in?
Stop when the growth is widespread, when it returns soon after the surface has been dried, or when it sits on timber you cannot see the back of. A kit will not point to a leaking gutter, a failed extractor, or a slow weep behind a bath. Retest with the same kit, the same exposure, and a similar time of day only after the damp source has actually changed.
Related pages
Sources
Public UK sources used for this comparison, last reviewed in October 2026.
- GOV.UK: damp and mould, health risks for rented housing (retrieved October 2026)
- English Housing Survey 2024 to 2025, housing quality (retrieved October 2026)
- Awaab’s Law: guidance for tenants in social housing (retrieved October 2026)
- HHSRS (England) Regulations 2005 (retrieved October 2026)
- NHS inform: damp and mould indoors (retrieved October 2026)
- Shelter England: damp and mould in rented homes (retrieved October 2026)
- RICS consumer guide: damp and mould (retrieved October 2026)
- UK Centre for Mould Safety: choosing a surveyor (retrieved October 2026)
- University of Connecticut EHS: facts about DIY mould test kits (retrieved October 2026)