What is the difference between reassurance air testing and clearance air testing?

Reassurance air testing is conducted during asbestos removal work to check that the enclosure is still containing fibres effectively, typically after a significant disturbance or at regular intervals. Clearance air testing is performed after the removal is complete and the area has been visually inspected, as part of the four-stage clearance procedure. The clearance test uses a specific sampling strategy (e.g., static samples in the work area) and must achieve a fibre concentration below 0.01 fibres/ml to pass.

How long does an air sample need to be taken for during clearance testing?

For clearance testing, the minimum sample volume is 1000 litres, which at a typical flow rate of 2 litres per minute requires a sampling time of at least 500 minutes (8 hours and 20 minutes). However, longer sampling times may be needed if the flow rate is lower or if the laboratory requires a larger volume. Always follow the method specified in HSG248 and your laboratory's procedures.

Can I use a personal air sampling pump for static air monitoring?

Yes, personal air sampling pumps can be used for static monitoring as long as they are calibrated to the correct flow rate (typically 2 l/min) and are fitted with a suitable cyclone or filter holder. However, for static monitoring, the pump should be placed in a fixed location, not worn by a person. Ensure the pump is capable of running for the required duration without battery failure.

What should I do if a clearance air test fails (fibre count above 0.01 f/ml)?

If a clearance air test fails, the area must be re-cleaned and re-inspected visually. The source of contamination should be identified and rectified (e.g., missed debris, damaged enclosure). A second clearance test can then be performed. If repeated failures occur, consider using TEM analysis to identify the fibre type, as non-asbestos fibres may be causing the high count. The certificate of reoccupation cannot be issued until a satisfactory result is obtained.

Is it necessary to wear RPE during air monitoring?

Yes, appropriate respiratory protective equipment (RPE) should be worn during air monitoring if there is any risk of asbestos fibre release. Even during clearance testing, if the area has not yet been certified as safe, RPE is required. The analyst should follow the site-specific risk assessment and wear at least a half-face respirator with P3 filters. However, once the clearance certificate is issued, RPE may no longer be needed.

What records must I keep after completing air monitoring?

You must keep a detailed record of all air monitoring activities, including the date, location, sampling method, flow rate, sampling time, filter identification, and results. For clearance procedures, you must also document the visual inspection findings, any remedial actions taken, and the final certificate of reoccupation. These records should be retained for at least 40 years, as per CAR 2012, and be available for inspection by the HSE.

Practical, fibre counting, air sampling and clearance procedures for asbestos analysts

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vocational

This element equips asbestos analysts with the hands-on competencies needed to perform air sampling, fibre counting by phase contrast microscopy (PCM), and four-stage clearance testing in accordance with HSG 248 and ISO 17025. Candidates learn to set up and calibrate sampling equipment, prepare and read microscope slides, apply fibre counting rules, and conduct thorough visual inspections and air tests to certify areas fit for reoccupation.

Learning Outcomes

Assessment Guidance

Key Skills

Key Terms

Assessment Criteria

Assessment criteria

RSPH Level 3 Award in asbestos air monitoring and clearance procedures

Topic Overview

The RSPH Level 3 Award in Asbestos Air Monitoring and Clearance Procedures is a specialised qualification for professionals involved in asbestos management, particularly those conducting air monitoring and issuing certificates of reoccupation after asbestos removal. This award covers the theoretical and practical aspects of background, reassurance, and leak testing, as well as the four-stage clearance procedure required by the Control of Asbestos Regulations 2012 (CAR 2012). It is essential for ensuring that asbestos removal work has been completed safely and that the area is fit for reoccupation, protecting workers and the public from exposure to airborne asbestos fibres.

This qualification sits within the broader context of occupational health and safety in the construction and building services sector. It is typically taken by asbestos analysts, surveyors, and removal supervisors who need to demonstrate competence in air sampling and clearance testing. The course emphasises the importance of correct sampling strategies, use of appropriate equipment (such as phase contrast microscopy), and adherence to HSG248 (Asbestos: The Analysts' Guide). Mastery of these procedures is critical for regulatory compliance and for preventing asbestos-related diseases, which remain a leading cause of occupational death in the UK.

Students will learn to plan and conduct air monitoring in various scenarios, interpret results, and complete the required documentation, including the certificate of reoccupation. The award also covers quality assurance, record keeping, and the legal responsibilities of the analyst. By the end of the course, students should be able to confidently perform the four-stage clearance procedure, understand the limitations of air monitoring, and communicate findings effectively to clients and regulators.

Key Concepts

Core ideas you must understand for this topic

→Four-stage clearance procedure: Stage 1 (pre-clean visual inspection), Stage 2 (full visual inspection and reassurance air testing), Stage 3 (post-clean visual inspection and leak testing), Stage 4 (final visual inspection and certificate of reoccupation).
→Air monitoring types: background (before work), reassurance (during work), leak (checking containment), and clearance (after work). Each has specific sampling locations, durations, and flow rates as per HSG248.
→Phase contrast microscopy (PCM): the standard method for counting asbestos fibres on membrane filters, with a limit of detection typically around 0.01 fibres/ml for a 1000-litre sample.
→Negative pressure units (NPUs) and HEPA filters: critical for maintaining containment during removal, with air monitoring used to verify their effectiveness.
→Quality assurance: includes calibration of pumps, use of blank samples, and participation in proficiency testing schemes (e.g., RICE) to ensure accurate results.

Learning Objectives

What you need to know and understand

Carry out asbestos fibre counting and air sampling, Carry out clearance procedures

Assessment Criteria

Key criteria assessors look for in your portfolio

Award credit for demonstrating correct calibration of air sampling pumps using a calibrated flow meter both before and after sampling, with results recorded on the sample data sheet.
Look for accurate preparation of PCM slides using acetone–triacetin mounting method, ensuring an even distribution of fibres and minimal air bubbles.
Expect full application of counting rules: only fibres meeting the 3:1 aspect ratio and being >5 µm long are counted, avoiding crossing boundaries, and counting at least 100 fibres or 100 graticule areas.
In clearance procedures, mark for systematic performance of all four stages: preliminary assessment, thorough visual inspection, air monitoring, and final assessment, with documentation completed at each stage.

Assessment Guidance

Guidance for achieving higher grades

💡Practice using the Walton–Beckett graticule to measure fibre dimensions; time yourself to develop efficient scanning patterns.
💡Memorize the four clearance stages and the pass criteria: <0.01 fibres/cm³ for reassurance sampling, and area visually clean.
💡When counting, systematically scan across the slide to avoid double-counting or missing fields; use a tally counter if allowed.
💡Familiarize yourself with the RSPH candidate handbook assessment methods—much of the practical is assessed via direct observation and written portfolio evidence, so ensure your logbooks are detailed.
💡Know the four-stage clearance procedure in detail, including the specific actions and documentation required at each stage. Examiners often ask candidates to describe the steps in order and explain the purpose of each.
💡Be able to calculate air sample volumes and fibre concentrations. Practice converting flow rates (e.g., 2 l/min) and sampling times (e.g., 4 hours) into total volume, and then into fibres/ml using the count from PCM. Show all working out.
💡Understand the limitations of PCM and when to recommend TEM analysis. For example, if a sample has a high fibre count but the fibres appear non-asbestiform, you should advise on further analysis. This demonstrates higher-level thinking.

Common Mistakes

Common errors to avoid in your coursework

Forgetting to zero the rotameter before measuring flow rate, leading to inaccurate sample volumes.
Counting non-fibrous particles as fibres due to poor microscope setup or not adjusting the vernier scale correctly.
Overlooking the requirement to stop counting at 100 fibres even if graticule areas remain uncounted, or conversely, counting fewer than 100 areas when fibre count is low.
During clearance, failing to check plant and equipment left in situ for surface contamination, or not moving movable objects during the visual inspection.
Misconception: Air monitoring alone can confirm an area is safe. Correction: Visual inspection is equally important; the four-stage clearance procedure requires both visual checks and air testing. A clearance certificate cannot be issued without a satisfactory visual inspection.
Misconception: All asbestos fibres are visible under PCM. Correction: PCM cannot distinguish between asbestos and non-asbestos fibres, nor can it detect fibres thinner than about 0.2 µm. Transmission electron microscopy (TEM) is needed for definitive identification, but PCM is the standard for clearance testing.
Misconception: Leak testing is only required during removal. Correction: Leak testing should be performed whenever the integrity of the enclosure is compromised, such as after a tear in the polythene sheeting or after a worker exits the enclosure.

Frequently Asked Questions

Common questions students ask about this topic

Before You Start

Prior knowledge that will help with this topic

•A good understanding of the Control of Asbestos Regulations 2012 (CAR 2012), particularly the duties to manage asbestos and the requirements for licensed work.
•Knowledge of asbestos types, their properties, and health effects (e.g., asbestosis, mesothelioma, lung cancer). This is typically covered in the RSPH Level 3 Award in Asbestos Management or equivalent.
•Basic mathematics skills for calculating volumes and concentrations, as well as familiarity with scientific units (e.g., litres, minutes, fibres/ml).

Key Terminology

Essential terms to know

Carry out asbestos fibre counting and air sampling, Carry out clearance procedures

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Practical, fibre counting, air sampling and clearance procedures for asbestos analysts

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Examiner Marking Points

Practical, fibre counting, air sampling and clearance procedures for asbestos analysts

Assessment criteria

Topic Overview

Key Concepts

Learning Objectives

Assessment Criteria

Assessment Guidance

Common Mistakes

Frequently Asked Questions

What is the difference between reassurance air testing and clearance air testing?

How long does an air sample need to be taken for during clearance testing?

Can I use a personal air sampling pump for static air monitoring?

What should I do if a clearance air test fails (fibre count above 0.01 f/ml)?

Is it necessary to wear RPE during air monitoring?

What records must I keep after completing air monitoring?

Before You Start

Key Terminology

Ready to learn?

Related Topics in ROYAL SOCIETY FOR PUBLIC HEALTH vocational Construction & Building Services

Practice and Procedure in Adjudication for the Construction Industry

Production of an Enforceable Decision by an Adjudicator in the Construction Industry

The Application of English Law and the Law of Contract, Tort and Evidence to Adjudication in the Construction Industry

The Application of the Law of Adjudication to the Construction Industry