Exposure Monitoring: Why It’s Required and What to Test For in Different Workplaces

Exposure monitoring is a core component of occupational hygiene and COSHH compliance. It provides objective evidence of what workers are actually exposed to during normal activities and whether existing control measures are effective in practice.

While exposure monitoring is sometimes commissioned following regulatory feedback or inspection, it is most effective when used proactively — to understand risk, support proportionate control strategies, and protect worker health over the long term.

This article explains why exposure monitoring is carried out, what typically needs to be tested for in different industries and workplaces, and how monitoring fits alongside controls such as LEV testing and wider COSHH management.

What Is Exposure Monitoring?

Exposure monitoring involves measuring the concentration of hazardous substances in workplace air, usually within the breathing zone, during normal work activities. The aim is to determine whether exposure is adequately controlled when assessed against health-based criteria such as occupational exposure limits. Exposure monitoring is not about identifying the presence of a substance alone. It considers:

• Magnitude of exposure

• Duration and frequency

• Variability between tasks and workers

• How exposure occurs in practice

This information is essential where exposure cannot be reliably estimated from process knowledge alone.

Why Exposure Monitoring Is Required

Exposure monitoring is typically required where:

• Hazardous substances are present with established exposure limits

• There is uncertainty around the effectiveness of existing controls

• Processes or materials have changed

• Work patterns vary significantly between tasks or individuals

• Regulatory feedback requests evidence rather than assumption

Under COSHH, employers must be able to demonstrate that exposure is adequately controlled. Regulators expect exposure data to be collected using approved methods and data to be interpreted professionally.

What to Test For: Common Workplace Contaminants

The substances requiring monitoring depend on the processes involved and the way exposure occurs. Common examples include the following.

Welding Fumes, Metal Fumes, and Rubber Fume

Exposure monitoring is commonly required in fabrication, manufacturing, and maintenance environments where welding or hot processes are carried out. Monitoring may assess:

• Total inhalable and respirable particulates

• Specific metal constituents

• Process-related fumes

This is particularly important where exposure varies by task, material, or ventilation effectiveness.

Respirable Crystalline Silica (RCS)

RCS exposure is a significant health risk in construction, masonry, glass manufacturing, and similar industries. Monitoring is often required where:

• Cutting, grinding, or drilling is carried out

• Materials containing silica are disturbed

• Controls rely on assumptions rather than measured exposure

• Control levels must be determined

RCS exposure assessment typically focuses on respirable dust fractions and task-based exposure.

Wood Dust and Flour Dust

Dusts are common in woodworking, biomass handling, food production, and bakery environments. Exposure monitoring helps assess:

• Total inhalable dust exposure

• Task-specific peaks

• Effectiveness of local exhaust ventilation

Monitoring is particularly important where exposure varies across different activities or shifts.

Solvent Vapours

Solvent vapour exposure can arise from painting, printing, cleaning, and manufacturing processes. Monitoring is often required where:

• Volatile substances are used regularly

• Exposure cannot be estimated reliably from usage data

• Multiple solvents are present

Assessment focuses on understanding real exposure during use, not just product composition.

Acid Mists (Including Chromic Acid)

Acid mists are commonly encountered in electroplating and surface treatment operations. Exposure monitoring in these settings focuses on:

• Mist generation during processes

• Effectiveness of capture and ventilation systems

• Potential for inhalation exposure during routine tasks

Isocyanates

Isocyanates are are associated with serious health effects. They are commonly encountered in painting, polyurethane foams and resins, and manufacturing environments. Monitoring may be required where:

• Spraying or mixing is carried out

• Engineering controls and PPE are relied upon

• There is uncertainty around exposure control

Given the health implications, professional interpretation is essential.

General Gases and Vapours

Exposure monitoring may also be required for a wide range of gases and vapours arising from combustion, chemical processes, or confined environments. Assessment focuses on:

• Identifying exposure pathways

• Understanding task-related exposure

• Supporting proportionate control measures

Other Environments and Hazards

Exposure monitoring may also be required in more specialised settings, including:

• Anaesthetic gases in healthcare environments

• Microbiological hazards and animal allergens in research and farming

• Mixed dusts and vapours in complex industrial settings

In these environments, monitoring strategies are often highly task- and context-specific.

Exposure Monitoring and LEV Testing

Exposure monitoring and LEV testing address different but complementary questions.

• LEV testing confirms whether a ventilation system is performing as designed

• Exposure monitoring confirms whether that performance is actually controlling exposure in practice

In many cases, exposure monitoring identifies where further LEV assessment, modification, or testing is required. Equally, LEV test results can help in the interpretation of exposure data.

The Role of Occupational Hygiene Expertise

Designing, carrying out, and interpreting exposure monitoring requires professional judgement. Qualified occupational hygienists, typically holding licentiate or higher qualifications awarded by the British Occupational Hygiene Society (BOHS), are trained to:

• Design proportionate monitoring strategies

• Select appropriate sampling methods

• Interpret results against health-based criteria

• Consider multiple exposure routes

• Translate data into practical COSHH recommendations

The value lies not just in the measurements, but in how the results are used to inform control strategies.

Developing Robust COSHH Strategies

Exposure monitoring is most effective when integrated into a broader COSHH management approach. This may include:

• Review of existing controls

• LEV testing and assessment

• Evaluation of exposure routes beyond inhalation

• Development of proportionate control recommendations

• Ongoing review as processes change

This structured approach supports defensible compliance and long-term protection of worker health.

A Proportionate Approach to Exposure Monitoring

Not every workplace requires routine exposure monitoring. In some cases, existing controls and previous assessments may provide sufficient assurance. In others, monitoring is essential to understand risk and guide effective control. The key is ensuring that monitoring is targeted, proportionate, and professionally interpreted.

NOHH Ltd provides exposure monitoring across a wide range of airborne contaminants, delivered by qualified occupational hygienists and supported by LEV testing and COSHH compliance guidance. Contact us below for a free consultation from a qualified hygienist.