ToolsAsbestosAir Sampling

Pump Flow Rate Drift Checker

Check whether your air sampling pump stayed within the plus or minus 5% flow rate tolerance required by HSG248. Instant pass/fail result.

Last updated 3 March 2026

About this tool

Check whether your air sampling pump flow rate stayed within the acceptable drift tolerance between pre- and post-sampling measurements. For flow rates ≥2 L/min the tolerance is ±5%; for flow rates <2 L/min the tolerance is ±10%. If the flow rate drifts beyond the applicable limit, the sample is invalid and must be repeated.

How to use

Enter the pre-sampling and post-sampling flow rates as measured by your rotameter or flow meter. The tool will calculate the percentage drift, apply the correct tolerance based on the flow rate, and tell you whether the sample is valid.

Reference

HSG248 — Asbestos: The analysts’ guide for sampling, analysis and clearance procedures (HSE, 2021). Flow rate drift tolerance is ±5% for rates ≥2 L/min and ±10% for rates <2 L/min.

Revision history

3 March 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.

Pre-sampling flow rate (L/min)

Post-sampling flow rate (L/min)