Asbestos air testing and air samples ‑ analysis with a JEOL SEM‑EDS electron microscope

What does asbestos air testing mean?

In asbestos air testing, a calibrated pump draws a set volume of indoor air through a filter cassette, so that fibres in the air are caught on the filter. In the laboratory the filter is examined with an electron microscope: the fibres are counted, and their elemental composition shows whether they are asbestos. When the sampler reports the volume of air collected, the fibre concentration in the air can be calculated from the result. An air sample differs from a material sample: a material sample tells you whether a building material contains asbestos, while an air sample tells you whether fibres have got into the air.

When is asbestos air testing needed?

• Clearance testing after removal work: confirming before handover that no asbestos fibres remain in the air after the removal work.
• Suspected exposure: when asbestos-containing material has, for example, been sanded, drilled or broken without protection and you want to know whether there are fibres in the air.
• Employee exposure monitoring: during asbestos removal and survey work.
• Indoor air investigations and property transactions: when fibres are suspected of spreading into the premises or the condition of an older property needs to be established.

How is the air sample taken, sent and analysed?

The air sample is taken on site by a qualified asbestos surveyor or occupational hygienist using a calibrated pump and a filter cassette. The sampler records the volume of air collected, seals the cassette and sends it to the laboratory by post. Onelab examines the filter with a JEOL SEM-EDS electron microscope (a scanning electron microscope with energy dispersive elemental analysis), which also detects very thin fibres and tells asbestos apart from other fibres chemically. The result is sent by email, typically on the day the sample arrives.

2026 law change concerns air samples

With the implementation of the EU asbestos exposure directive (EU) 2023/2668, fibres in air samples must be counted with an electron microscope from 21 December 2026, and a light microscope (PLM) alone is no longer sufficient. Onelab's JEOL SEM-EDS electron microscope has been in use from the start - you need no transition period. Read more about the 2026 change in the law.