How Air Monitoring Supports Workplace COSHH Exposure Assessments

Under the Control of Substances Hazardous to Health (COSHH) Regulations 2002, UK employers are legally required to identify hazardous substances, assess the risks they present, and ensure that exposure is either adequately controlled or reduced As Low As Reasonably Practicable (ALARP). A workplace COSHH exposure assessment forms part of this process by evaluating how workers may come into contact with hazardous substances during their activities.

Where workplace environments work with, produce or store airborne contaminants such as dusts, fumes, vapours or gases, occupational hygienists may use workplace air monitoring as one of several tools to help assess exposure risks. In particular, workplace air monitoring can provide useful quantitative data about how contaminants are generated, dispersed, and controlled during real working conditions.

Air Monitoring and Workplace Exposure Assessments

Workplace air monitoring measures airborne contaminants generated during specific activities or processes. Depending on the monitoring method used, the results may help occupational hygienists evaluate personal exposure levels, assess the effectiveness of existing engineering controls, identify areas of higher exposure risk, or understand how contaminants move within a workplace environment.

Importantly, data represents conditions at the time of sampling, and therefore should be interpreted alongside other factors such as work patterns, employee behaviour, maintenance standards, ventilation performance, and existing control measures.

When used appropriately, air monitoring can help organisations:

• assess inhalation exposure during specific tasks or activities
• identify processes or locations associated with elevated airborne contamination
• evaluate whether engineering controls such as Local Exhaust Ventilation (LEV) are functioning effectively
• investigate the migration or escape of contaminants beyond the immediate task area
• support reviews of respiratory protective equipment (RPE) suitability
• prioritise improvements to workplace controls and exposure reduction strategies

Selecting the most appropriate monitoring approach is critical, as different techniques provide different types of information and must reflect actual workplace conditions and working practices.

Personal and Background Air Sampling

Different air monitoring approaches may be used depending on the hazardous substances present, the nature of the work activities, and the objectives of the exposure assessment.

Personal air sampling measures airborne contaminants within an individual worker’s breathing zone during specific tasks or over defined periods. This type of monitoring is particularly useful when assessing personal exposure against applicable Workplace Exposure Limits (WELs), including both Time Weighted Average (TWA) exposures and, where relevant, Short Term Exposure Limits (STELs).

Background air sampling measures airborne contamination within the wider workplace environment rather than within an individual breathing zone. Although background sampling cannot typically be compared directly against WELs, it can provide valuable information about how contaminants disperse throughout a workspace, how effectively ventilation systems contain or remove airborne hazards, and whether contaminants are escaping from specific control systems.

Used together, personal and background air monitoring can help occupational hygienists build a broader understanding of inhalation exposure risks within a workplace: personal sampling shows what people actually breathe, whilst background sampling shows how contaminants behave in the space as a whole.

Notably, workplace air monitoring data should always be interpreted within the context of the wider workplace COSHH exposure assessment, which involves additional approaches such as visual auditing, process reviews, discussions with employees, and assessments of existing control measures. This is where specialist occupational hygiene support can make a measurable difference.

How Envirochem Can Help

Effective workplace COSHH exposure assessments require more than exposure data alone. They rely upon an understanding of how substances are used, how contaminants are generated, how workers interact with processes, and how effectively existing controls reduce exposure risks in practice.

With more than three decades of experience delivering occupational hygiene services, our BOHS qualified Occupational Hygiene specialists, listed on the Professional Standards Authority register, work closely with clients to assess exposure risks across a wide range of industries and workplace settings. Our team can often deliver multiple occupational hygiene services during a single site visit, helping organisations build a more complete understanding of workplace risks whilst minimising operational disruption.

Whether you are reviewing existing control measures, investigating potential exposure concerns, or preparing for a workplace exposure assessment under COSHH, Envirochem can help. Visit our Occupational Hygiene Services page to learn more about our Workplace Air Monitoring services, or contact our team to discuss your requirements.