Understanding COSHH: Protecting Employees from Poor Air Quality

The Control of Substances Hazardous to Health Regulations 2002, commonly referred to as COSHH regulations 2002 , place clear and legally enforceable duties on UK employers to reduce workers’ exposure to dangerous substances.

Across almost every industry, harmful substances can be present or generated from various processes or work activities, making COSHH compliance essential for safeguarding health.

Exposure to hazardous substances, whether through inhalation, skin absorption, ingestion or eye contact, can cause long term health issues without immediate symptoms, meaning problems can go unnoticed for years. Under COSHH regulations, air monitoring is vital because it provides objective evidence that exposure is adequately controlled.

What Do the COSHH Regulations Require Employers to Do?

Under COSHH, employers must first identify hazardous substances used in, or generated by, their process or work activities. Substances can include dust, gases, vapors, mists, biological agents and chemicals.

Once identified, employers are required to:

• Carry out a COSHH risk assessment
• Prevent exposure where reasonably practicable
• Adequately control exposure
• Ensure controls are maintained and used correctly
• Provide information, instruction and training
• Carry out monitoring of exposure were required
• Implement health surveillance when appropriate
• Review risk assessments regularly

Under the COSHH Approved Code of Practice (ACOP), UK employers are required to demonstrate through evidence that exposure is genuinely controlled in real working conditions to protect workers from injury and ill health. This is also enforced by the Health and Safety Executive (HSE).

What is Air Quality Monitoring and Why is it Important?

Air monitoring is the process of measuring the concentration of potentially hazardous substances in workplace air. It focuses on what employees are actually breathing rather than what is assumed to be present. Monitoring can take many forms, including:

• Personal air monitoring – This is achieved by the employee wearing a small, battery-operated sampling pump to measure their exposure to hazardous airborne substances.
• Static air monitoring – The process of measuring airborne contaminants – such as dust, fumes or vapors – at fixed, stationary locations within a workplace or environment.
• Short term or long-term sampling – Involves gathering data or air samples over a few minutes to several hours to measure acute exposures.

Air monitoring helps employers to:

• Demonstrate compliance with Control of Substances Hazardous to Health
• Confirm that control measures such as Local Exhaust Ventilation (LEV) are effective
• Identify hidden or underestimated exposure
• Validate COSHH risk assessments
• Protect workers from occupational ill health

In many cases, air monitoring is the only reliable way to know whether control measures are truly effective and are working to reduce or remove exposure.

How Do You Know if Your Business Needs Air Quality Monitoring?

Not every workplace automatically requires air quality monitoring. However, many businesses fall under COSHH regulations without realising it. You are likely to need air quality monitoring if your business uses substances with workplace exposure limits (WELs). In such cases, COSHH expects you to understand and control exposure. Monitoring is the most practical way to demonstrate this.

A full list of substances and WELs is available on the HSE website (EH40/2005 workplace exposure limits). Cross referencing substances from the list against substances used or produced by your workplace and the WELs for each will reveal if air quality monitoring is required.

Air quality monitoring is also important where exposure:

• Varies throughout the day
• Dependson manual tasks or operator technique
• Reliesheavily on ventilation or PPE/RPE
• Cannot be easily assessed by observation alone

You should also consider air monitoring if:

• Workers report symptoms such as coughing, headaches, or breathing issues
• There are strong smells, visible dust or fumes
• New substances, equipment or processes have been introduced
• Production volumes or work methods have changes

If you are unsure whether exposure is adequately controlled to remove or reduce risk, that uncertainty alone is often a sign that monitoring is required.

When Should Air Monitoring Be Carried Out?

Air monitoring is not a one-off exercise, COSHH requires exposure control to be managed over time and monitoring should reflect this.

Monitoring should be considered:

• During or after a COSHH risk assessment to establish baseline exposure
• When new substances or processes are introduced
• After changes to ventilation systems or control measures
• If work patterns, volumes or layouts change
• When controls are suspected to be failing
• Following health surveillance findings
• Periodically when exposure is significant and controls are critical

The frequency of monitoring depends on risk, substance type and the reliability of controls. Higher risk activities require more regular verification of control measures and compliance.

Regular monitoring helps ensure that the standards don’t slowly slip and exposure workers to increased risk.

Strengthening COSHH Compliance Through Monitoring and Control

Effective COSHH management relies not only on identifying hazardous substances and implementing suitable control measures but also on ensuring that those controls are working in practice. Air monitoring plays a vital role in this process, providing objective data on the levels of airborne contaminants and verifying whether exposure is being adequately controlled.

By incorporating regular air monitoring into workplace risk management, organisations can:

• Detect emerging issues early
• Safeguard employee health
• Maintain compliance with legal requirements
• Reduce the risk of enforcement action

COSHH legislation exists to ensure substances hazardous to health are properly controlled. Proactive monitoring and ongoing review remain central to meeting that legal duty.