Four-Stage Clearance

A 4SC is a process carried out to ensure that the most hazardous asbestos removal projects have been undertaken to a high standard of safety, the area is free from debris and the air in the removal area is at a safe level to take down the enclosure.
It is essential the analyst is completely independent as they will produce the certificate of reoccupation.


Stage 1

This stage involves a preliminary check of the site condition and completeness of the project/job against the plan of works.

A check will also be undertaken of the licensed asbestos removal contractors (LARC) license, notification to the HSE (ASB5), training records, equipment and other records.

A check must be undertaken of the enclosures integrity.

The transit route and decontamination facilities must also be checked.

A visual inspection must also be carried out using the viewing panel, cctv, pictures etc of the completion of the works.

Stage 2

A visual inspection must be carried out inside the work area/enclosure. The analyst will estimate the required time to complete the works, record this information and explain if the time frame deviates from this.

The asbestos removal supervisor initially carries out a visual check to ensure they are satisfied the area is clean. They then issue a hand over form to the analyst to say the area is ready for inspection.

A thorough investigation must then be carried out by the analyst of the enclosure to ensure all areas are dry and stripped areas or surfaces are clean with no remaining dust or debris visually present. The analyst will use mirrors, a bradawl and strong torch to access difficult areas.

The analyst must ensure that there is no evidence within the enclosure of settled dust or debris.

Stage 3

Clearance Air Testing

At this stage an airborne fibre monitoring test must be carried out within the enclosure or work area.

The test must ensure that the area meets the necessary standards of 0.01 fibres per cubic centimetres of air.

This test is conducted under disturbance to simulate normal occupied conditions, this is normally done by brushing all surfaces to raise any fibre settled dust. Air is drawn through a filter at a set flow rate and the number of fibres counted.

The number of pumps is calculated by the volume of air to be sampled onsite and microscopes are used to count the number of respirable fibres.

Stage 4

This is the final stage of the assessment which is conducted after the works have been completed but prior to the enclosure being dismantled.

Once the air test has passed, the enclosure can be dismantled including removal of all the equipment and materials. This stage will also include checking the DCU (Decontamination Unit).

The analyst will visually examine the work and transit areas again to ensure that no covered dust or debris remains or any further asbestos material has been exposed. Following this stage being passed by the analyst, a certificate of reoccupation will be issued.

What Happens if a Stage Fails?

If the visual test fails work will be performed before the test is repeated. Traditionally the analyst would assist with this, however with the recent revision of HSG248, the analyst must not assist. If the remedial work exceeds 10 minutes, the stage must start again.
If the air test fails, the analyst will inspect the area for the cause of the failure, remedial works will be undertaken and the air test will be taken again.

The analyst will complete and issue documentation showing the results of the test/tests, performance the contractor at each stage and this documentation will detail any failures or remedial actions that have been undertaken on the certificate of re-occupation.

What is a certificate of reoccupation?

A certificate of reoccupation (also known as a certificate for reoccupation) is required before an area can be safely reoccupied following licensed asbestos removal works without PPE and decontamination procedures.

This certificate will be issued by the analyst once the four stages of the 4SC have been successfully completed.

Inspection of the Decontamination Unit (DCU)

When stage 4 has been passed, the clearance on the DCU (also known as hygiene facility) can begin. The inspection of the DCU can also be started on successful completion of stage 3 of the 4SC however, if at any point the hygiene unit is required to be used again during the 4th stage the inspection of the DCU must start again.

The analyst will visually inspection and air test the unit including a disturbance of all the surfaces in the dirty area and shower area. Only stages 2 & 3 are required in relation to the inspection of the DCU.

EMS Analysts

EMS analysts undertaking a 4SC clearance are all P403 & P404 qualified, with over 5 years of experience. They are able to provide a comprehensive and supportive approach to ensuring the safety of works on site.

Our high standards of quality and service delivery and ability to work effectively alongside contractors on behalf of our client allow us to ensure a high level of service delivery. We are UKAS accredited to ISO17025; it is a legal requirement to be accredited to ISO17025 for air testing.

Our analysts provide a range of 24 hour services including project management and auditing as well as air testing.

This service allows you peace of mind and includes reassurance inspections and air quality monitoring, personal exposure and four-stage clearance resting for certificates of re-occupation following asbestos removal works.

Air Monitoring works are undertaken in line with ISO17025 and are carried out in accordance with HSE guidance ‘Asbestos: The analysts guide for sampling analysis and clearance procedures (HSG248). This guidance can be found here.


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