What is four-stage clearance testing?

The four-stage clearance process is mandatory after licensed asbestos removal. Stage 1: preliminary check of completeness. Stage 2: thorough visual inspection. Stage 3: disturbed air sampling. Stage 4: final assessment and Certificate of Reoccupation. All four stages must be passed before the area can be reoccupied.

What is the clearance fibre level?

The clearance indicator is 0.01 fibres per cm³ of air, measured by phase contrast microscopy. This is ten times below the workplace exposure limit (WEL) of 0.1 f/cm³ and must be achieved before reoccupation is permitted.

Who carries out air monitoring?

Air monitoring and clearance testing must be conducted by an analyst who is independent of the removal contractor. Our analysts are experienced in supporting both removal contractors and building owners with independent oversight.

When is air monitoring needed beyond removal works?

Air monitoring is also used for reassurance testing during nearby works, background monitoring to establish baseline levels, personal monitoring for exposure assessment, and leak testing during licensed removal to check enclosure integrity.

Air Monitoring & Clearance Testing

Professional air monitoring and four-stage clearance certification following asbestos works.

Air tests can be arranged at short notice

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When Is This Required?

Required under CAR 2012 and HSG248 during and after asbestos removal works. Four-stage clearance is mandatory before an area can be reoccupied following licensed removal.

Who Needs This?

Licensed asbestos removal contractors

Building owners overseeing removal projects

Project managers coordinating clearance

Local authorities enforcing compliance

Purpose

To assess airborne fibre concentrations and verify safe reoccupation following asbestos removal or disturbance, in accordance with HSG248 and CAR 2012.

Comprehensive Overview

Air monitoring and clearance testing are essential components of any asbestos removal or remediation project. Under the Control of Asbestos Regulations 2012 and HSG248 guidance, air monitoring must be conducted during and after asbestos works to verify that fibre levels remain below the control limit, and a formal four-stage clearance process is mandatory before reoccupation of areas where licensed asbestos removal has taken place.

Background Monitoring: Before asbestos works commence, we establish baseline fibre concentrations in the surrounding area. This provides a reference point for comparison during and after works, and confirms that background conditions are within acceptable limits before the enclosure is erected.

Leak Testing: During licensed removal works, air samples are taken around the enclosure perimeter to detect any fibre leakage. This ongoing monitoring ensures the integrity of the containment is maintained throughout the removal process. Any breach is immediately identified and reported to the removal contractor for corrective action.

Reassurance Monitoring: Personal and static air samples are taken in occupied areas adjacent to asbestos works to provide reassurance to building occupants and employers that fibre levels remain within safe limits. Results are compared against the workplace exposure limit (WEL) of 0.1 fibres per cm3.

Four-Stage Clearance: Following licensed asbestos removal, we conduct the full four-stage clearance procedure as required by HSG248. Stage 1: preliminary check of site condition and completeness of removal. Stage 2: thorough visual inspection under controlled lighting conditions. Stage 3: disturbed air sampling to simulate worst-case conditions. Stage 4: final assessment confirming the area is safe for reoccupation. A Certificate of Reoccupation is issued only when all four stages are satisfactorily completed.

Fibre Counting and Analysis: All air samples are analysed using phase contrast microscopy (PCM) in accordance with the WHO method (HSG248). Fibre counts are reported with full analytical data and compared against the relevant clearance indicator (0.01 fibres per cm3 for clearance testing).

Our analysts are experienced in supporting both licensed removal contractors and building owners, providing the independent oversight required for regulatory compliance and client confidence.