Quick answer
Asbestos air monitoring measures airborne fibre concentration to HSG248. There are five types: background (before works), leak (during works), reassurance (after minor disturbance), personal (worker exposure) and four-stage clearance (after licensed removal). Results are expressed in fibres per millilitre of air (f/ml).
The five test types
HSG248-defined air monitoring:
| Type | When | Typical use |
|---|---|---|
| Background | Before works | Establish baseline |
| Leak | During works | Enclosure integrity |
| Reassurance | After minor disturbance | Confirm safe re-entry |
| Personal | During works | Worker exposure |
| Clearance | After licensed removal | Four-stage clearance |
Method and thresholds
Air is drawn through a filter membrane over a defined period; fibres are counted under phase contrast microscopy. The clearance certificate limit is 0.01 f/ml. Personal exposure control limit is 0.1 f/ml over 4 hours.
Frequently asked questions
Common questions
Is air monitoring UKAS accredited?+
Yes — for compliance, only UKAS-accredited analysts should conduct air testing.
How long does a test take?+
1–4 hours on site; PCM analysis usually same day.
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