ToolsAsbestosAir Sampling

Clearance Indicator Calculator

Enter your Stage 3 air sample results to check whether the enclosure passes the 4-stage clearance criteria. 80% and 100% rules checked automatically.

Last updated 25 February 2026

About this tool

Enter your Stage 3 air sample results and instantly determine whether the enclosure passes the 4-stage clearance procedure. The tool checks both pass criteria from HSG248: at least 80% of results must be below 0.010 f/ml, and ALL results must be below 0.015 f/ml.

How to use

Enter the fibre concentration for each air sample taken during Stage 3. You can add as many samples as needed. The tool will automatically evaluate both clearance criteria and give you a clear pass or fail result. A minimum of 2 samples is required.

Pass criteria

HSG248 specifies two criteria that must both be met for clearance to pass. First, at least 80% of air sample results must be below 0.010 f/ml. Second, every single result must be below 0.015 f/ml. If either criterion is not met, the enclosure must be re-cleaned and re-tested.

Reference

HSG248 — Asbestos: The analysts' guide for sampling, analysis and clearance procedures (HSE, 2021). The 4-stage clearance procedure is described in detail, with Stage 3 being the air monitoring phase.

Revision history

25 February 2026: Initial release.

Disclaimer

This tool is provided for educational and general information purposes only. It is not a substitute for professional engineering advice, design or verification.

Diggy and its contributors are not licensed engineering consultants and no results generated by this tool should be used directly for construction, design or safety-critical decisions.

All values and outputs are based on published empirical correlations and should be independently checked and confirmed by a qualified geotechnical engineer before use.

By using this tool, you accept full responsibility for how you interpret and apply the information provided.

Spotted an error? Let us know.

Sample results (f/ml)