EH40 – Workplace Exposure Limits 2005 (2020 edition).

EVCentral Expert Commentary

EH40 is arguably one of the most frequently referenced occupational hygiene documents in the UK and forms the basis of many workplace exposure assessments.

The publication contains Workplace Exposure Limits (WELs), which represent airborne concentrations of hazardous substances that employers should not exceed. The limits are intended to support COSHH compliance and help organisations assess whether exposure control measures are performing effectively.

However, one of the most common misunderstandings surrounding EH40 is the belief that compliance with a WEL automatically means workers are adequately protected.

In reality, COSHH requires employers to prevent exposure where reasonably practicable and, where prevention is not possible, to adequately control exposure. A Workplace Exposure Limit should therefore be viewed as one part of a wider exposure-control strategy rather than the sole indicator of acceptable risk.

For LEV professionals, EH40 provides important context when evaluating engineering controls. Exposure monitoring results are often compared against WELs to determine whether LEV systems, process controls and management arrangements are effectively reducing worker exposure.

The document is particularly important when assessing exposure to:

Welding fume constituents
Respirable crystalline silica (RCS)
Wood dust
Flour dust
Metalworking fluid mist
Solvents and VOCs
Isocyanates
Pharmaceutical substances
Process dusts and powders

EH40 should not be used in isolation. Exposure monitoring data should be interpreted alongside:

Process observations
LEV performance data
COSHH assessments
Health surveillance findings
Workplace practices
Occupational hygiene judgement

From a LEVCentral perspective, EH40 supports a fundamental principle of defensible exposure control:

Exposure limits provide a benchmark, but effective worker protection requires competent assessment, suitable engineering controls and ongoing verification of performance.

Key Learning Points

What Is a Workplace Exposure Limit?

A WEL is the maximum concentration of a hazardous substance permitted within workplace air over a specified reference period.

Long-Term and Short-Term Limits

EH40 contains:

Long-Term Exposure Limits (typically 8-hour reference periods)
Short-Term Exposure Limits (typically 15-minute reference periods)

Both may be relevant depending on the nature of the work activity.

Exposure Monitoring Supports Compliance

Personal exposure monitoring is often required to determine whether worker exposure is below applicable limits.

WEL Compliance Does Not Replace COSHH Duties

Employers must still reduce exposure as far as reasonably practicable even where exposures remain below a published limit.

Further Resources

Recommended Learning

LEVCentral Observation

EH40 is often viewed simply as a table of exposure limits, but its true value lies in how it supports evidence-based decision making.

When combined with competent occupational hygiene assessment, effective LEV design, exposure monitoring and health surveillance, Workplace Exposure Limits provide a valuable benchmark for protecting worker health.