What air monitoring measures
Air monitoring measures the concentration of asbestos fibres in the air. Small battery-powered pumps draw air through membrane filters at a controlled flow rate. After sampling, these filters are sent to a laboratory where analysts count the fibres under a microscope. The result is expressed as fibres per millilitre of air (f/mL).
The purpose is straightforward: to confirm that asbestos removal work isn't releasing dangerous fibre levels into occupied areas, and to verify that a work zone is safe to reoccupy once removal is complete.
When is air monitoring required?
In Australia: Air monitoring is required for all licensed asbestos removal work (both Class A and Class B). It must be carried out by a licensed asbestos assessor who is independent of the removalist. This independence requirement exists to prevent conflicts of interest.
In New Zealand: Air monitoring requirements apply to Class A (restricted) asbestos removal. For Class B work, monitoring is recommended but not always mandatory depending on the nature and scale of the job. The monitoring must be carried out by someone independent of the removal contractor.
Types of air monitoring
There are several stages of monitoring during a removal project. Each serves a different purpose.
Background monitoring is done before removal work starts. It establishes the baseline fibre level in and around the work area. This gives you a reference point. If fibre levels during removal are significantly higher than the background, that's a problem that needs investigation.
Leak testing (or perimeter monitoring) happens during the removal itself. Monitors are placed around the outside of the enclosed work area, in adjacent occupied spaces, and at building air intake points. These samples confirm that the containment is working and fibres aren't escaping into occupied areas.
Clearance monitoring takes place after removal is finished and the work area has been cleaned. The enclosure is left in place, and air is sampled inside it. If fibre levels are below the clearance threshold, the area passes. This is the final check before the enclosure comes down and the space is handed back for normal use.
Some projects also include personal exposure monitoring, where samplers are attached to individual removal workers to measure their exposure. This is primarily the removalist's responsibility under workplace health and safety law, but you may see the results referenced in the overall monitoring report.
What the results mean
In both Australia and New Zealand, the workplace exposure standard for asbestos is 0.1 f/mL as a time-weighted average over eight hours. For clearance after removal, the threshold is typically 0.01 f/mL, which is ten times lower than the exposure standard.
If clearance monitoring returns a result below 0.01 f/mL, the area has passed. If it's above that threshold, the removalist must re-clean and the area must be re-tested. The assessor will not issue a clearance certificate until the result comes back below the threshold.
Results from leak testing during removal should show levels consistent with normal background levels (which are typically well below 0.01 f/mL). An elevated reading during removal triggers an immediate response: the work stops, the containment is checked and repaired, and monitoring resumes before work continues.
Who pays for air monitoring?
Air monitoring is usually a separate line item from the removal quote. Sometimes the removalist coordinates the booking, but the assessor must be independent and should invoice you (the building owner or manager) directly. This keeps the independence requirement clean. Budget for air monitoring as part of any removal project, as it's a mandatory cost, not an optional extra.
What you should receive
After the project, the air monitoring professional should provide you with a written report covering all monitoring stages: background, leak, and clearance results. This report, along with the clearance certificate, becomes part of your compliance records. Keep these documents with your asbestos register. You may need to produce them during regulatory inspections or property transactions.