Understanding Your Mould Lab Report

Your AirTrap samples have been analysed and the report has landed in your inbox: a results page, a data table full of Latin genus names and spores per cubic metre, and images taken from your slides. This guide walks through the report section by section – what the values are, how the “elevation” ratings come about, and what the report can and cannot tell you.

In short: the report counts and identifies the spores on each slide, converts the counts to spores/m³, compares every indoor sample with the outdoor reference from the same property and highlights where the indoor air carries more of a mould type than the outside air – especially types that grow on water-damaged materials. It gives you the values and the images; the interpretation for the building stays with you.

How the report is structured

Every report has the same three layers.

1. The results page

One graphic per air sample shows whether the sample had no elevation, a slight elevation or a major elevation of mould spores compared with the outdoor reference. Surface swabs get a similar graphic showing whether mould growth is present on the sampled surface or not. Where the lab thinks an explanation helps, a short note from the Sporecyte analyst appears next to the result.

2. The data table

Behind the graphics sits the raw data the rating is based on: spores/m³ per mould type, for every indoor sample and for the outdoor reference. The table is ordered by relevance, and cells are highlighted – orange for a slight elevation, red for a major elevation – so the eye lands on what matters.

• Predominantly indoor – water related: mould types that grow on water-damaged building materials and are very rarely found in outdoor air. Any meaningful count indoors points to moisture and growth inside the building.
• Indoor/outdoor: types that can grow inside and outside. Here the comparison with the outdoor reference decides.
• Predominantly outdoor: types that normally grow outdoors and very rarely on building materials. Elevated indoor values are usually carried in from outside.
• Particulates: everything on the slide that is not a mould spore – pollen, skin fragments, fibres, dust. Useful context for the sampling conditions.

3. Trace images

For every sample the report shows an overview image of the whole trace – the strip of particles the cassette deposited on the slide – and a zoomed-in image of an interesting area. These are pictures of your actual slide, not stock images; they are what lets you show a client what was in the air rather than just tell them.

The key figures explained

Spores/m³. The analyst counts the spores identified on the slide; the count is converted to a concentration using the sampled air volume – with the standard AirTrap protocol that is 15 l/min for 5 minutes, i.e. 75 litres. A concentration lets you compare rooms, dates and properties with each other and with the outdoor air.

Mould type. Spores are identified by their morphology on the slide, which usually means to genus or to a group – Aspergillus/Penicillium, for instance, are reported together because their spores cannot be told apart under the microscope. The type often matters more than the raw number: a modest count of a water-damage indicator says more about the building than a large count of a common outdoor type in summer.

The outdoor reference. The single most important line in the table. Outdoor air always carries spores, and their mix changes with the season and the weather. Only the comparison of indoor with outdoor tells you whether spores were carried in or produced inside. That is why the protocol asks for an outdoor sample per property – and why the report contains no interpretation when there is none.

Why there is no limit value

Neither Germany nor the UK has a legally binding limit value for mould spores in indoor air. Assessment is comparative: the German UBA mould guideline, for example, works with the indoor–outdoor comparison, the spectrum of types found and moisture indicators rather than a single threshold, and clearance measurements after remediation follow the WTA guideline 4-12. The report’s elevation ratings apply exactly this logic to your samples – they tell you where the indoor air deviates from the outdoor reference and how strongly.

What the report does not do

The report gives you the values, the ratings and the images. It does not make recommendations for the building, because it does not know it: it has not seen the moisture readings, the construction, the history of the damage or the occupants. That assessment is yours – as surveyor, remediation contractor, property manager or building biologist – and the report is designed to be a clean, documented piece of evidence inside it.

What to do with the result

• No elevation: no indication of an indoor source in the sampled room at the time of sampling. Note it in the file; if a complaint persists, sample again under different conditions or extend to further rooms.
• Slight elevation: look at which types are elevated. Indoor/outdoor types slightly above the reference often trace back to ventilation, textiles or house dust; a water-related type, even at a low count, deserves a look at moisture and hidden growth.
• Major elevation: locate the source – moisture measurement, inspection behind furniture and fittings, surface swabs on suspicious areas – and plan remediation. After remediation, a clearance sample under the same conditions documents the result.
• Occupants with symptoms: the report is a sound basis for a conversation with a doctor; it is not a diagnosis.

Presenting the report to your client

You can hand over the PDF as it is, walk the client through the results page, or fold the values into your own report. The trace images and the highlighted table do most of the explaining; the outdoor comparison is the argument that convinces. Keep the PDF with the property file – the sampling parameters, dates and images make it useful again when you re-test after remediation.

Frequently asked questions

How do I read the report quickly?
Results page first: the rating per sample. Then the table: which types are highlighted and in which category. Then the outdoor line for the comparison. The trace images are for showing, not for counting.

What does a slight or major elevation mean?
The indoor concentration of that mould type is above the outdoor reference – slightly or strongly. The category tells you how to weigh it: water-related types indoors matter even at low counts.

Why is there no interpretation on my report?
Because no outdoor reference sample was submitted. Without it the lab cannot say whether spores came from outside; the values are still reported.

Can I re-test after remediation?
Yes – a clearance sample under the same conditions (same room, same duration, outdoor reference) shows whether the remediation worked. Refill packs contain everything for repeat sampling.

How the analysis works   Refill packs

Written by the AirTrap team on the basis of the Sporecyte report format used for AirTrap samples. The report supports the assessment of a professional; it does not replace it.