If you suspect mould in your home but can’t see any visible growth, a DIY air test is an effective way to assess the air quality and detect airborne mould spores.
An air test measures what you breathe, making it especially useful when symptoms are present but the source is hidden. To get a reliable result, it’s essential that the test is carried out correctly.
Below, we guide you through the process step by step.
What Is an Air Test?
A DIY air test measures mould spores and microorganisms suspended in the air. Unlike a surface test, it does not require visible mould and is ideal for detecting hidden issues behind walls, under floors, or in poorly ventilated rooms.
An air test is particularly useful if you experience:
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Musty or damp smells
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Headaches, fatigue, or irritation when indoors
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Symptoms that improve when leaving the property
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Previous water damage or ongoing condensation issues
Before You Start – Important Guidelines
To ensure accurate results, please follow these rules carefully:
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Keep the test refrigerated until use
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Do not open windows or doors for at least 1 hour before testing
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Turn off ventilation systems, air purifiers and fans
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Do not test immediately after cleaning
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Avoid touching the agar surface inside the test
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Use one test per room
How to Perform the Air Test – Step by Step
Step 1: Choose the Right Room
Select the room where you suspect poor air quality or where symptoms are strongest. Bedrooms, living rooms and basements are common test areas.
Place the test at breathing height (around 1–1.5 metres from the floor), ideally in the centre of the room.
Step 2: Prepare the Test
Remove the test from the fridge and let it acclimatise at room temperature for a few minutes.
Carefully remove the lid without touching the agar surface.
Step 3: Expose the Test to the Air
Leave the test open for exactly 60 minutes.
During this time:
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Do not stay in the room
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Avoid movement that may disturb the air
Airborne spores will naturally settle onto the agar surface.
Step 4: Close and Seal the Test
After 60 minutes, carefully replace the lid and seal the test as instructed.
Step 5: Incubate the Test
Place the closed test in a warm, dark location at normal room temperature.
Do not refrigerate after exposure.
Step 6: Read the Result
Check the test after 3–5 days.
You may see colonies appearing as dots, spots or fuzzy growth in different colours.
How to Interpret Your Result
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No or very few colonies
→ Normal background levels -
Several colonies
→ Elevated mould presence, further investigation recommended -
Many colonies / rapid growth
→ Strong indication of indoor mould contamination
The number, size and type of colonies matter – not just whether growth appears.
If you’re unsure, we’re happy to help interpret the result.
What to Do If the Test Shows Growth
Mould in the air is often caused by:
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Excess moisture or condensation
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Poor ventilation
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Cold surfaces and thermal bridges
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Past or hidden water damage
If growth is detected, we recommend:
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Improving ventilation and humidity control
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Identifying and fixing moisture sources
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Considering a professional inspection
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Performing additional tests if needed
Disposal of the Test
Once the test period is complete, the test can be disposed of with normal household waste.
Need Help Interpreting Your Result?
If you’d like help understanding your test or advice on next steps, contact us:
📞 +44 20 4638 9811
We’re happy to guide you – no obligation.