How to carry out a COSHH assessment

Oct 21, 2021 | Health and Safety

COSHH stands for the Control of Substances Hazardous to Health Regulations, and it is the law that requires employers to control substances that are potentially hazardous to health. This includes completing a COSHH assessment to identify harmful substances in your workplace.

Most businesses use substances or products that are mixtures of substances. Some processes create substances. These could cause harm or illness to employees, contractors and other people.

What is a COSHH assessment?

A COSHH assessment aims to identify the hazards posed by harmful substances in your workplace, and helps you to implement control measures to reduce the risks. Performing a COSHH assessment can protect employees, managers, and members of the public from exposure to harmful substances.

COSHH assessments should look at the substances your workplace uses, creates or produces, how they could affect individuals working with or near them, and how you could reduce exposure or eliminate it completely. Assessments should highlight the risks and act as a guideline to inform and educate individuals about substances used in the workplace, and the efforts you are taking to eliminate health risks.

Does my workplace need a COSHH assessment?

If your workplace uses, creates or produces harmful substances, then you need to complete a COSHH assessment.

The Control of Substances Hazardous to Health regulations require businesses to complete a COSHH assessment if they are using or creating any harmful substances in the workplace. 

COSHH assessments are required by law according to the Control of Substances Hazardous to Health Regulations. The regulations state that employers are prohibited from carrying out any work which is liable to expose any employees to any hazardous substance unless they have completed the following steps:

  1.  Has made a suitable and sufficient assessment of the risk
  2.  Created a plan of the steps required to be taken to reduce or eliminate this risk.
  3.  Implemented control measures to reduce or eliminate risks.

A COSHH assessment should be carried out before any activities take place that uses, involves or exposes employees to substances that are hazardous to health.

How to carry out a COSHH assessment:

Below we will talk about these four steps and how they contribute to making an effective COSHH risk assessment that will help your business avoid accidents at work:

1. Collect information and identify hazards

2. Identify individuals at risk, and under what circumstances

3. Evaluate the risks and decide control measures

4. Review and revise the risk assessment

1. Collect information and identify any hazards

Identifying hazards is the first step towards controlling them, and in turn, reducing risks in your workplace. The hazards that will be relevant to your COSHH assessment will be hazardous substances such as chemicals and gases. The assessment will also cover items that may not be labelled clearly as hazardous, such as flowers and fungi.

Identify which substances are used in your workplace, and which of these could be harmful to health. You can find out this information by:

  • Obtaining the safety data sheet or other sources of information
  • Asking the supplier for information about the product
  • Looking at industry information about the product
  • Visiting trusted sources such as HSE or NHS websites.

2. Identify individuals at risk, and under what circumstances

Once you have identified the hazards around your workplace, it becomes easier to work out who might be at risk. Exposure to each hazard will pose different amounts of risk depending on the substance, the concentration of that substance, and how often the individual is exposed.

You need to consider anybody who might come into contact with the substance, not just employees. Think about:

  • Employees
  • Contractors
  • Customers
  • Site visitors
  • Office workers
  • Supervisors and managers
  • Residents or people working in the vicinity
  • Cleaning and maintenance staff
  • Members of the public

3. Evaluate the risks and decide control measures

Once the risks in your workplace have been identified, you’ll need to think about how they could affect individuals who are working in the vicinity.

You need to consider the following factors:

  • The potential of a substance to cause harm.
  • The likelihood of exposure.
  • How often exposure is likely to occur.
  • Level, duration and methods of exposure.

When the risks have been identified, it will be easier to look at how each risk could cause harm to an employee, and then set out precautions to follow avoid this happening.

You should look at the ways you can prevent exposure to hazardous substance. for example, is there a less harmful substance you could use?

Some of the control measures you could apply to the workplace include the following (via HSE):

Changing the process to reduce risk

  • Consider whether you can change the process you use to reduce or eliminate the risk of exposure.


  • Enclose the process or activity to minimise the escape or release of the substance
  • Use closed transfer and handling systems and minimise handling of materials
  • Extract emissions of the substance near the source

Systems of work

  • Restrict access to necessary individuals
  • Plan the storage of materials, and use appropriate containers. Check that storage containers are correctly labelled and that incompatible materials, for example acids and caustics, are separated
  • Plan the storage and disposal of waste


  • Exposure to hazardous substances can occur during cleaning, so plan and organise the workplace so that it can be easily and effectively cleaned
  • Smooth work surfaces will allow easy cleaning
  • Have the right equipment and procedures to clear up spillages quickly and safely
  • Clean regularly using a ‘dust-free’ method – vacuum, don’t sweep


4. Review and revise the risk assessment

You should regularly revise and review your risk assessment to ensure that all individuals are educated about the risks and subsequent control procedures. By monitoring incident rates and control measures, you will be able to judge whether your current control methods are effective, need to be improved, or new control measures need to be put in place.

Your risk assessment should be reviewed regularly to ensure that the risk of staff being harmed by hazardous substances has not changed and that no further control measures are needed. It should also be reviewed if any changes occur in your business that may increase the risk of exposure to harmful substances.




When making a COSHH assessment, you should consider:

  • What substances are used, created or produced in your workplace that could be hazardous to health
  • Which individuals are put at risk and under which circumstances
  • Control measures and alternative methods
  • Whether your workplace requires COSHH training 
  • Review and revise agreements

COSHH Training


This COSHH training course is ideal for those who wish to work in environments with hazardous substances

Health & Safety Newsletter

Subscribe to our newsletter to receive news, upcoming course information, and important updates.