Quick answer
Use exposure monitoring where the assessment shows it is needed to demonstrate adequate control or protect workers’ health, or where specific requirements apply. Define the question, method and representative conditions with competent support. Area screening, personal sampling and health surveillance answer different questions; a number without context is not a reliable control decision.
Define the purpose and applicable duty
GB COSHH regulation 10 sets monitoring conditions, change/regular review and specific scheduled requirements, including an alternative-evaluation provision where adequate control can be demonstrated appropriately.
HSENI COSHH guidance explains the NI framework. Use the relevant requirements and competent assessment rather than assuming every labelled chemical needs the same annual air test.
Choose the measurement for the question
HSE monitoring guidance distinguishes indicators, personal air exposure and biological monitoring. A stationary area measurement can help locate contamination but is not automatically representative of a worker’s exposure.
Define substance/form, route, people, task, timing and control conditions. Do not use a consumer sensor or an unrelated test merely because it produces a convenient live reading.
Plan a representative strategy
| Area | Question |
|---|---|
| Scope | Which workers/tasks/conditions must the evidence represent? |
| Method | Is sampling/analysis suitable and sufficiently sensitive? |
| Timing | Does it capture relevant variation, peaks and reference periods? |
| Context | What production, controls and unusual events occurred? |
| Interpretation | What uncertainty and applicable criteria affect the decision? |
| Action | Who assesses results and authorises necessary changes? |
Obtain occupational-hygiene or other competent specialist help where required. This is not a sampling protocol or universal frequency.
Interpret an example in context
Illustrative example: a quiet-period area sample is presented as evidence for a busy task with workers close to the source. Check whether the strategy represents the actual exposure question before drawing a conclusion.
If findings indicate inadequate control, act promptly and investigate the method/equipment/work system. Repeating a test until a preferred result appears is not a sound response.
Retain evidence and review changes
Keep the strategy, method, conditions, results, interpretation and actions. Apply the correct retention/access requirements, including the GB distinction for identifiable personal-exposure records, and check NI rules separately.
Communicate relevant findings appropriately. Keep health surveillance separate: it addresses work-related health effects through a suitable scheme, not the airborne concentration itself. Review changes and whether improvements remain effective.
Next steps
- Define the legal/risk-based need and precise evidence question.
- Use a suitable competent representative strategy.
- Interpret findings with task context and uncertainty.
- Act, record and review effectiveness/changes.
Read the official practical guidance — Use the current source alongside the procedures for your own business.