Guidance
Workplace exposure monitoring is the measurement of how much of a hazardous substance workers breathe in during their work. This guide explains what it involves and when it is required.
Driven by
COSHH Reg 10
Measures
Breathing-zone exposure
Compared to
EH40 limits
Method
Personal sampling
Workplace exposure monitoring measures the concentration of an airborne hazardous substance — such as dust, fume, vapour or gas — in the air that a worker actually breathes. The result is compared with the relevant workplace exposure limit to judge whether controls are adequate.
It is the objective, measured counterpart to a COSHH risk assessment: rather than estimating exposure, it quantifies it with calibrated equipment and accredited laboratory analysis.
Under Regulation 10 of COSHH, employers must monitor exposure where it is needed to protect health, where a workplace exposure limit could be exceeded, or where they need to confirm that control measures are working. In many industrial settings these conditions are routinely met.
Monitoring is also good practice after any change to a process, material or control, and at sensible intervals to confirm that protection is maintained over time.
A small calibrated pump is worn by the worker, drawing air through a sampling head in the breathing zone for a representative shift. The sample is analysed and the exposure expressed as an 8-hour time-weighted average, with short-term sampling for substances that have a 15-minute limit.
Workers are grouped into similar exposure groups under BS EN 689 so that a representative sample reliably describes the whole group rather than just one individual.
The report states the measured exposures, the compliance position against the limit, whether existing controls are adequate, and a recommended re-monitoring interval — defensible evidence for the HSE, insurers and clients.
Where COSHH applies, Regulation 10 makes monitoring a duty in defined circumstances — so for many employers it is effectively required.
A COSHH assessment identifies hazards and controls; exposure monitoring measures the actual exposure to confirm those controls work.
