Asbestos Air Testing & Clearance Certificate

What is Asbestos Air Testing?

Asbestos air testing is the measurement of airborne asbestos fibre concentrations following licensed removal work. It is carried out by an independent analyst — completely separate from the contractor who undertook the removal — to confirm that the area is safe to reoccupy. All air testing is conducted by UKAS-accredited analysts in accordance with the HSE's Analysts' Guide (HSG248).

The Four-Stage Clearance Procedure

Before a licensed asbestos removal enclosure can be dismantled and the area reoccupied, a four-stage clearance procedure must be completed:

• Stage 1 — Visual inspection: The independent analyst inspects the inside of the cleared enclosure to confirm that all visible asbestos debris has been removed and surfaces cleaned. The enclosure must pass this stage before air sampling begins.
• Stage 2 — Background air sampling: Air samples are collected from outside the enclosure to establish a background fibre concentration.
• Stage 3 — Enclosure air sampling: Air samples are collected from within the cleared enclosure while the NPU is still running. Samples are analysed by the UKAS-accredited laboratory.
• Stage 4 — Clearance certificate: If fibre concentrations are at or below the clearance criterion (currently 0.01 fibres per millilitre), a clearance certificate is issued. The enclosure can then be dismantled and the area reoccupied.

When is a Clearance Certificate Required?

A clearance certificate is required following any licensed asbestos removal project before the area is reoccupied. Lenders, insurers, building control officers, and local planning authorities will typically require a clearance certificate as evidence that removal has been properly completed. It is also standard practice for commercial tenants, landlords, and building contractors to require a clearance certificate before handback of an area.

Re-Inspection Air Testing

Outside of the formal four-stage clearance procedure, air testing can also be arranged for re-inspection purposes — for example, where asbestos is known to be present and its condition is being actively monitored, or where a disturbance incident has occurred and background fibre levels require confirmation.