How to Conduct COSHH Assessment in 7 Steps

A cleaning spray in a cupboard, flour dust in a bakery, welding fumes on a construction site and chemicals produced during a process can all create health risks. Knowing how to conduct COSHH assessment helps you identify those risks before they lead to ill health, absence, enforcement action or a preventable incident.

COSHH stands for the Control of Substances Hazardous to Health. Employers have a legal duty to assess risks from hazardous substances and put suitable controls in place. A COSHH assessment should not be treated as a form to complete and file away. It is a practical process that informs how people work, what equipment they use and what training they need.

What a COSHH assessment needs to achieve

A suitable and sufficient assessment considers the substance, the task, the people involved and the controls required. It should show that you have identified harmful exposure, considered who may be affected, and chosen measures that reduce risk as far as reasonably practicable.

The assessment must cover substances brought into the workplace, such as cleaning products, adhesives, paints and fuels. It must also consider substances created by work activities. Wood dust, silica dust, welding fume, mist from spraying and biological agents are common examples.

COSHH does not generally cover asbestos, lead or radioactive substances, as these are governed by separate regulations. However, the wider principle remains the same: understand the hazard, assess exposure and control it properly.

How to conduct COSHH assessment: 7 practical steps

1. Identify hazardous substances and processes

Start by walking through the workplace and speaking to the people who carry out the work. Review stores, cupboards, workstations, plant rooms and vehicles. Check purchasing records as well as labels and safety data sheets supplied by manufacturers.

Do not limit the review to products marked with an obvious hazard symbol. Some substances can cause harm through repeated low-level exposure, while others become hazardous when heated, mixed, sprayed, cut, sanded or disturbed. For example, a solid material may create harmful airborne dust during machining.

Create a clear inventory that records the substance or process, where it is used, who uses it and how often. This provides a sensible starting point and makes future reviews easier.

2. Understand the health hazards

Safety data sheets are useful, but they are not a COSHH assessment on their own. They explain a product's hazardous properties and offer handling guidance. Your assessment must apply that information to the actual conditions in your workplace.

Consider both immediate and long-term effects. A substance may irritate the eyes or skin, trigger asthma, cause dermatitis, harm internal organs or increase the risk of cancer. Think about all possible routes of exposure: breathing in dust, vapour, mist or fume; skin contact; eye contact; injection through a puncture wound; and accidental swallowing.

Pay particular attention to substances with workplace exposure limits, sensitising properties, corrosive effects or serious chronic health consequences. These often require tighter controls, monitoring or health surveillance.

3. Decide who could be exposed and how

Look beyond the employee directly using the substance. Colleagues working nearby, cleaners, maintenance teams, contractors, visitors and members of the public may also be affected. A poorly ventilated area can allow vapours or dust to travel well beyond the immediate task.

Consider workers who may be at greater risk, including young people, new or expectant mothers, people with existing respiratory conditions and anyone with damaged skin. The purpose is not to exclude people from work unnecessarily. It is to make sure controls are appropriate and that individual needs are considered.

Be specific about each task. Decanting a chemical from a large container, spraying it, cleaning a spill and disposing of waste can present different levels of exposure from normal use.

4. Evaluate the level of risk

Risk depends on the hazardous properties of the substance and the likely level of exposure. Ask how much is used, how often the task takes place, how long it lasts, whether the process is enclosed, and whether workers are likely to breathe in or touch the substance.

A small quantity of a highly hazardous material can still require careful controls. Equally, a low-hazard product used continuously in a confined space may present a significant risk. Avoid relying on generic wording such as “use with care”. Your assessment should explain what could go wrong in the real working environment.

For more complex activities, you may need specialist advice. This is particularly relevant where exposure limits apply, local exhaust ventilation is needed, or employees report symptoms that could be linked to work.

5. Choose controls using the right order

The most effective control is to remove the hazard altogether. Can the task be avoided, automated or changed? If not, consider substituting the substance for a less hazardous alternative. A lower-hazard cleaning product or water-based coating may reduce risk, but only if it is suitable for the job and does not introduce a different problem.

Where the substance must remain in use, control exposure at source. This could include enclosed processes, local exhaust ventilation, extraction on tools, closed transfer systems or reduced quantities. Good housekeeping, safe storage, clear labelling and planned waste disposal also matter.

Personal protective equipment should be the last line of defence, not the main solution. Gloves, goggles and respiratory protective equipment can be necessary, but they depend on correct selection, fitting, use, cleaning, replacement and supervision. Disposable gloves may not protect against every chemical, while an unsuitable mask can provide false reassurance.

6. Record the findings and communicate them

If you employ five or more people, you must record significant findings from the risk assessment. In practice, written COSHH assessments are useful for any organisation because they provide a clear reference point for supervisors and workers.

A good record identifies the substance or task, the people at risk, the harmful effects, the controls in place, any further action needed and the date for review. Keep the wording clear enough for the people doing the job to understand.

Training should cover more than where the assessment is stored. Workers need to know the hazards, the control measures, what PPE is required, how to use equipment safely, and what to do if there is a spill, leak or exposure incident. Accessible, accredited online health and safety training can help organisations provide consistent knowledge across dispersed teams, but it should support rather than replace task-specific instruction.

7. Check controls and review the assessment

A COSHH assessment is only effective if its controls work in practice. Supervisors should check that extraction systems are used, containers stay labelled, PPE is available and workers follow the agreed method. Local exhaust ventilation requires thorough examination and testing at appropriate intervals, commonly every 14 months for many systems, although some processes require more frequent checks.

Review the assessment when there is a change in substance, supplier, process, equipment, staffing or working conditions. Review it sooner if there is an incident, a near miss, a complaint of ill health or evidence that controls are not effective. Even where nothing changes, set a sensible review date so assessments do not become outdated.

Common mistakes to avoid

The most common error is copying a safety data sheet into a generic template without considering the actual task. Another is relying entirely on PPE when a safer process or engineering control is available. Organisations can also overlook short-duration tasks such as maintenance and cleaning, despite these often involving close contact with concentrated substances.

Poor communication creates its own risk. An assessment kept in a manager's folder will not protect a worker who has not been shown how to use extraction, choose suitable gloves or respond to a spill. Make the findings practical, visible and part of everyday supervision.

Build COSHH into everyday safe working

A well-conducted COSHH assessment gives people a safer way to carry out necessary work, rather than adding paperwork for its own sake. Start with the tasks that involve the highest hazard or greatest exposure, involve the people who know the work best, and act on what the assessment tells you. That is how compliance becomes meaningful protection for your workforce.