Key Facts: Legal Requirements
- A four-stage clearance procedure — including a clearance air test — is mandatory after all licensed asbestos removal work under CAR 2012.
- A background air test before licensed removal commences is legally required to establish baseline fibre levels.
- Personal air monitoring of workers during licensed removal is mandatory under CAR 2012 Regulation 18.
- The clearance criterion under CAR 2012 is 0.01 fibres per millilitre (f/ml) — any result above this requires re-cleaning and re-testing.
- The analyst carrying out clearance testing must be independent of the removal contractor and belong to a UKAS-accredited body.
What Is Asbestos Air Testing?
Asbestos air testing — also called airborne fibre monitoring or fibre counting — measures the concentration of asbestos fibres suspended in the air of a building or work area. Air samples are collected using calibrated pumps drawing air through a membrane filter, which is then analysed in a UKAS-accredited laboratory using phase contrast microscopy (PCM) or transmission electron microscopy (TEM).
The standard analytical method is MDHS101 (Methods for the Determination of Hazardous Substances 101), published by the HSE. MDHS101 defines the sampling and counting procedures that UKAS-accredited laboratories must follow when analysing asbestos air samples for clearance purposes.
When Is Air Testing Legally Required?
| Scenario | Test Type | Legally Required? |
|---|---|---|
| After licensed asbestos removal | Clearance air test | Mandatory |
| Before licensed asbestos removal | Background test | Mandatory |
| During licensed asbestos removal | Personal air monitoring | Mandatory |
| After NNLW disturbance (non-licensed work) | Reassurance test | Not mandatory — recommended |
Types of Asbestos Air Test
| Type | Purpose | When Required |
|---|---|---|
| Clearance air test | Confirm asbestos removal is safe | After all licensed removal work |
| Background test | Establish baseline fibre levels before work | Before licensed removal |
| Personal air sampling | Monitor worker exposure | During licensed removal works |
| Reassurance test | Give confidence after disturbance concerns | On request — not legally required |
The Four-Stage Clearance Procedure
After licensed asbestos removal work, a four-stage clearance procedure must be completed before the area can be reoccupied:
- Visual inspection to confirm the area is clean and free of visible debris
- Background air test taken before the enclosure is broken down
- Air test inside the enclosure once the contractor confirms removal is complete
- Final clearance certificate issued if results are below the clearance criterion (0.01 fibres/ml)
Who Can Carry Out Air Testing?
Clearance air testing after licensed removal must only be carried out by a UKAS-accredited body independent of the removal contractor. The analyst must hold BOHS P403 (surveying and sampling) or P404 (air monitoring and clearance) qualifications. You cannot use the same company that did the removal work to sign off on the clearance test.
The accrediting body must hold UKAS accreditation under ISO 17025 (for testing and calibration laboratories) or ISO 17020 (for inspection bodies), as appropriate to their scope of work. Only UKAS-accredited organisations can issue legally valid clearance certificates under CAR 2012.
What Do Air Test Results Mean?
The clearance criterion under the Control of Asbestos Regulations 2012 is 0.01 fibres per millilitre (f/ml). If the air test result inside the enclosure is at or below this level, the area is deemed safe for reoccupation and a clearance certificate can be issued.
If any sample exceeds 0.01 f/ml, the enclosure must be re-cleaned and retested. The contractor is responsible for the re-clean at their own cost. The cycle repeats until all results pass. Only then can the enclosure be broken down and the area reopened.
Cost of Asbestos Air Testing
| Test Type | Typical Cost |
|---|---|
| Clearance air test (small area) | £150 – £300 |
| Clearance air test (large area) | £300 – £800+ |
| Background air test | £100 – £200 |
| Reassurance air test | £150 – £350 |