Lab Analysis: How Your Mould Sample Is Tested

The air sample is taken, the cassette is capped and labelled. What happens to it now? Anyone sending a mould sample to a lab for the first time wants to know how a small slide turns into a reliable lab report – and how long that takes.

This article follows your AirTrap sample step by step: from registration through posting and analysis in the lab to the report in your inbox. It is written for private customers as much as for surveyors, remediation contractors and property managers who want to understand the method.

In short: you register your samples online and post them to Wokingham in the UK in the prepaid return envelope. There, every slide is scanned in full and analysed in the ISO/IEC 17025-accredited Sporecyte laboratory – AI-assisted and checked by a specialist. You receive the lab report by e-mail within 48 hours of arrival. The analysis is included in the price of the cassettes.

The process at a glance

Five steps lie between sampling and report. Two of them are yours, three are the lab's.

1. Register the samples. After sampling, enter each cassette in the online form: room, date, time and whether it is an indoor or an outdoor sample. The link to the form comes with your order confirmation.
2. Post the samples. All cassettes go into the prepaid, pre-addressed return envelope from the pack, caps closed. How to pack them and what belongs on the label is described on the sample return page.
3. Intake and scan. At Apacor in Wokingham, the company behind AirTrap, the samples are received, matched to your registration, and the slide from each cassette is scanned digitally.
4. Analysis. The digital slide is analysed in the ISO/IEC 17025-accredited Sporecyte laboratory: the spores are detected, identified and counted, and the result is checked by a specialist.
5. Report. Within 48 hours of the samples arriving, you receive the lab report as a PDF by e-mail.

How the sampling itself works – pump, cassette, outdoor sample – is explained on Indoor air measurement.

What happens in the lab

The AirTrap XL cassette is a spore trap: the pump draws room air through a narrow slit, the particles impact on a coated slide and stick to it. That trace is what the lab examines. The method is the total spore count as described in DIN ISO 16000-20.

• Whole-slide scan. The entire trace is digitised at high resolution – not just selected sections of it. The whole content of the trace goes into the analysis.
• AI-assisted identification. Image analysis locates the spores on the scan and assigns them, by shape, size and structure, to a genus or group – Cladosporium, Aspergillus/Penicillium or Stachybotrys, for example. It applies the same criteria to every sample.
• Specialist review. Before a report is released, a specialist at the lab checks the identification and the overall picture of the sample. The software makes the counting faster and more consistent; responsibility for the result rests with the person reviewing it.
• Conversion to spores per cubic metre. The spores counted are related to the volume of air sampled. With the standard protocol that is 15 litres per minute for 5 minutes, i.e. 75 litres. Arithmetically, 75 spores of one genus counted on the slide therefore correspond to 1,000 spores per cubic metre of air.

All spores are captured – including dead ones, which culture methods do not show but which can be just as allergenic. Identification is to genus or group level; no culture is grown, so there are no colony-forming units (CFU) and no identification to species. More on the platform behind the analysis: What is Sporecyte.

How long it takes

The total time has two parts: the post and the time in the lab. Both are easy to estimate.

• Transit. From Germany and the rest of the EU the return envelope is usually in transit to Wokingham for a few days.
• Lab. Within 48 hours of the samples arriving, the report is in your inbox.
• Overall. From posting to report you should usually allow about a week. The post is the largest and least predictable part of it.

Three things help avoid delays: register the samples before you post the envelope, so the intake can be matched immediately. Label every cassette legibly with room and time. And post the cassettes promptly after sampling, with the caps closed.

Compared with culture methods, where the samples first have to be incubated for several days, the total spore count is the faster method. That makes it suitable when a result is needed soon – before a flat is handed over, for instance, or to verify a remediation.

What the report contains

The report arrives as a PDF. For every sample it contains:

• the concentration in spores per cubic metre, broken down by genus or group;
• the comparison with the outdoor air: every indoor sample is set against the outdoor sample from the same day;
• an elevation rating – none, slight or major elevation relative to the outdoor air;
• images from the slide, showing what the lab saw.

The outdoor sample is not an extra but the yardstick. Without it the lab cannot put the indoor values into context, because spores are part of the air everywhere and their numbers vary with season and weather. So take an outdoor sample on every sampling day.

How to read the numbers, which genera point to moisture damage and what “slightly elevated” means in practice is explained in Understanding your mould lab report.

What the analysis costs

With AirTrap there is no separate lab fee: the analysis is included in the price of the cassettes. You order a complete set or a refill pack, and that pays for the analysis of every cassette – no invoice follows from the lab. So the cost of a measurement is known before you take the first sample.

For context: external labs in Germany usually charge for the analysis per sample. Lab prices of around €50 to €90 per air sample are common, plus the sampling itself – the pump, or the call-out of a competent person. Anyone measuring several rooms pays several times over accordingly.

Which pack makes sense depends on the number of samples: for a flat with two or three rooms plus outdoor air, a set of eight cassettes is enough; anyone who measures regularly uses the refill pack with 24 cassettes.

What the report does not do – and what comes next

A lab report is a measurement result, not an assessment of the building. It shows which spores were in the air and in what quantity – not where the mould is growing, why it is damp or what needs to be done. Those questions are answered by a competent person on site, a surveyor or building biologist for instance, for whom the report is an objective basis.

Nor is the report a medical diagnosis. Whether symptoms are connected with the indoor air is for a doctor to judge. And there is no legal limit value for mould spores in indoor air, in Germany or the UK; assessment is by comparison with the outdoor air and by the genera found, as the mould guideline of the German Environment Agency (UBA) describes.

What makes sense after the report depends on your situation:

• After a remediation: the report is the basis of the verification. The procedure is described in Clearance testing after mould remediation.
• As a tenant: keep the report and your photographs, and have the values interpreted professionally before you take steps towards your landlord. More in Mould: tenant rights and evidence.
• Questions about the report: if something is unclear, write to us via the contact page. We will explain what the report says – the assessment of the property stays with the competent person.

An elevated value is not a verdict but a pointer to where a closer look is needed. An unremarkable value is good news – but it is a snapshot of the air, not proof that there is nothing behind a wall.

Frequently asked questions about lab analysis

What does a mould lab analysis cost?
With AirTrap the lab analysis is included in the price of the cassettes; there is no separate lab fee. External labs in Germany usually charge per sample – around €50 to €90 per air sample is common, plus the sampling.

How do I order the analysis?
You do not need to commission anything separately. Order a complete set or a refill pack – the analysis is included. After sampling, register the cassettes via the link in your order confirmation and post them in the enclosed return envelope.

What exactly does the lab test?
The lab identifies and counts the mould spores on the slide – viable and dead alike – and assigns them to genera or groups. From that it calculates the concentration in spores per cubic metre and compares every indoor sample with the outdoor air. No culture is grown, so there are no CFU values and no identification to species.

Are mycotoxins or MVOCs measured too?
No. The analysis captures only what can be seen microscopically on the slide: spores and other particles. Mycotoxins, microbial volatile organic compounds (MVOCs) or bacteria require different sampling and methods; whether they are useful in a given case is for the competent person to decide.

Where is the lab?
Your samples go to Apacor in Wokingham in the UK, the company behind AirTrap; there they are received and scanned. The analysis is carried out in the ISO/IEC 17025-accredited Sporecyte laboratory, AirTrap's lab partner. More on the Laboratory partnership page.

See complete sets   Understanding your lab report

Written by the AirTrap team. Sources: DIN ISO 16000-20 (total spore count), ISO/IEC 17025 (requirements for testing laboratories), UBA guideline on the prevention, detection and remediation of mould in buildings (2017, updated 2024). This article does not replace medical advice or the assessment of a competent person.