Last updated: 08.02.21

What is a COSHH Assessment?

There are several different types of risk assessment that have to be carried out in a workplace in order to protect employees and minimise risk, particularly for those who work with hazardous substances. A COSHH assessment is a procedure that considers the risks of working with substances that can harm somebody’s health, and puts procedures in place that will ensure that the risks of working with a substance are minimised and a safe working environment is maintained.

What is COSHH?

The Control of Substances Hazardous to Health Regulations (COSHH) is a piece of health and safety legislation that outlines how employers and employees should handle, store, use and dispose of hazardous substances. They have been put in place in order to control the use of substances that pose a danger to people’s health and reduce exposure to these substances as much as possible to minimise risk. 

When is a COSHH assessment required?

To put it simply, a COSHH assessment is required whenever an individual or group in a workplace is using, producing or creating a substance that can be hazardous to health.

Under COSHH, employers have a legal obligation to carry out a risk assessment before their staff come into contact with any hazardous substances. Before work with or around the substance begins:

  • An assessment of the risk to the employees’ health must be made
  • Steps to minimise this risk must be identified and outlined
  • These health and safety measures must then be implemented

A risk assessment is required and COSHH control measures must be put in place before work takes place that could expose an employer, employees or customers to a hazardous substance. Neglecting this responsibility could put many people at risk of harm and lead to legal action if someone gets hurt, so it’s a necessary step before work begins.

How to do a COSHH assessment

The necessary steps to comply with COSHH and complete a risk assessment can be broken down into three different sections; identifying the hazards, identifying who may be harmed, and evaluating the risks and ways to reduce them. It is very similar to carrying out a regular risk assessment, but more specific knowledge is needed when identifying each hazardous substance and the specific risk to health that it poses. 

Part 1 - Identify the Hazards

The first step of any COSHH assessment involves identifying each of the hazardous substances present in the workplace that present a risk to the health and safety of employees or customers. 

A hazardous substance is any mixture or material that is corrosive, toxic or an irritant. In the workplace, these include substances that are directly used in work, substances that are produced because of work activities, substances that occur naturally and biological substances such as bacteria.

Substances can take the form of:

  • Chemicals
  • Products which contain chemicals
  • Gases
  • Dusts, vapours, mists or fumes
  • Microorganisms

A good place to start a COSHH assessment is by collecting the safety data sheets (SDS) of all the substances stored and used in the workplace, which outline the risks associated with each of them. Many chemicals also have hazard warning labels on their containers which contain relevant information about their hazardous properties.

For substances that are less obviously hazardous, employers should keep up to date with the latest health and safety guidance in their industry. There is also a lot of useful information provided by HSE that outlines certain hazardous substances associated with different industries, along with the EH40 Occupational exposure limits list which offers advice on reducing risk as well as identifying hazards.

Employers should make a list of every hazardous substance that is present in the workplace as a starting point for their COSHH report, consulting product manufacturers and industry specialists if needed. It is vital that every hazard is identified, no matter how small the risk.

Part 2 - Identify Who is at Risk

Once every potentially hazardous substance has been identified, the next step of the COSHH assessment is to identify who is at risk from these substances. Start with employees who work directly with the substances, then work outwards and consider every other person who may come into contact with them.

The assessment should consider:

  • Employees
  • Managers and supervisors of these employees
  • Contractors who may have to work with or around the substances 
  • Cleaning and maintenance staff that may come into contact with spillages, dust or residue
  • Site-visitors that may enter an area with hazardous substances 
  • People residing or working in the vicinity who may be inadvertently exposed

As well as identifying everyone who could be affected by hazardous substances, a COSHH report also needs to consider the different ways that these individuals may be harmed. This will be influenced by how harmful each substance is, how likely exposure is and the duration and level of exposure for each individual.

A substance’s level of harm will be outlined either on its label, on its safety data sheets, by the manufacturer or by industry health and safety guidance. Substances can also cause harm in several different ways, including inhalation, ingestion, coming into contact with the skin or eyes, or entering the body through cuts in the skin. 

Possible effects of exposure to hazardous substances can include:

  • Irritation of the skin and dermatitis in extreme cases
  • Allergic reactions to substances resulting in asthma
  • Loss of consciousness from inhaling hazardous fumes or gas
  • Infections from contact with biological agents
  • Cancer and other terminal illnesses from exposure to toxic substances

Substances that are more dangerous will need more severe COSHH procedures put in place to keep the workplace safe, such as PPE for employees and appropriate health and safety training

After identifying all the people who may be at risk and the ways in which they could be harmed, a COSHH assessment should outline the different levels of exposure and risk for each individual, dictated by how much they come into contact with a substance and how long they are exposed for.

Part 3 - Evaluate and Reduce Risks

At this stage in a COSHH assessment, the report should detail all of the hazardous substances that employees may be exposed to in the workplace and the different levels of risk that individuals visiting or working in the space may encounter. The most critical step of the assessment is to then evaluate each of these risks and hazardous scenarios, and decide how to minimise damage to health as much as possible.

Risk reduction should deal with the hazards that pose the most serious risk to health first. Actions can also be prioritised by considering which substances present the most immediate risks, and which will be the quickest to reduce.

When deciding how risks are to be controlled and reduced, traditionally the hierarchy of control is followed. This outlines 6 different ways of controlling risk from most effective to least effective, and is helpful in guiding what measures employers can put in place to minimise risk.

  1. Elimination - In some cases, it may be possible to completely eliminate exposure to hazardous substances by changing workplace processes and systems
  2. Substitution - If elimination isn’t possible, one of the easiest ways to reduce risk is to assess each of the hazardous substances that are used and consider whether a safer alternative can be substituted instead
  3. Isolation - If a substance cannot be substituted, employers can consider purchasing equipment which encloses a hazardous substance as it is used and therefore reducing exposure.
  4. Engineering - Even if total isolation isn’t possible, there may be physical changes that can be made to a process that removes risk, such as adding ventilation for example
  5. Administration - If an exposure risk is only minimal, administrative measures can be put in place such as providing employees with health and safety training, installing warning signs into the workplace and rotating staff who work with hazardous substances to reduce the duration of their exposure
  6. PPE - At the very minimum, individuals who are working directly with or around hazardous substances should be given appropriate personal protective equipment such as gloves, goggles and face masks

This hierarchy can be used to decide on appropriate COSHH control measures for every risk that has been identified. All of this information must be recorded and then implemented in the workplace before any hazardous substances are brought in.

The containment and storage of hazardous substances is another key part of a COSHH assessment, to ensure that certain substances are kept safe when not in use. Most hazardous products come with storage instructions, and these should be listed in a COSHH report along with safety measures to ensure that substances aren’t spilt or damaged as they are moved.

Finally, a COSHH assessment should ensure that safe cleaning procedures are implemented in areas where hazardous substances are used, so that cleaners are kept safe and that traces of substances aren’t left in the workplace.

Whose responsibility is it to carry out a COSHH assessment?

It is the overall responsibility of a workplace employer to manage COSHH procedures and health and safety measures, so it is their responsibility to organise and ensure that a COSHH assessment is carried out. The employer doesn’t have to be the one to do it, but they are in charge of nominating somebody competent to complete the assessment in their place.

If you are self-employed and work with hazardous substances in a profession such as hairdressing, for example, it is your responsibility to complete a COSHH assessment for your working environment and the substances that you handle.

In some cases, a COSHH assessment may require expert input or a specialist to complete. This may be the case if a workplace is particularly large and has multiple departments, a substance poses a significant risk, or a substance is being dealt with which is quite rare.


What does COSHH stand for?

COSHH stands for the Control of Substances Hazardous to Health Regulations and is a piece of legislation that was brought about in 2002 to regulate how dangerous substances were dealt with in the workplace.

What are COSHH records?

COSHH assessment records are copies of the risk assessment form that will have been completed to evaluate how hazardous substances are being used in the workplace and what steps are being taken to minimise risk. Records must be kept easily available and all employees must be able to access them if necessary.

What factors may trigger a review of a COSHH risk assessment?

A COSHH risk assessment may have to be reviewed if an accident happens in the workplace that involves a hazardous chemical, as you will be required to assess whether the accident could have been prevented and whether further measures are required to stop the incident happening again. A review of a COSHH risk assessment will also be required if a new hazardous substance begins to be used in the workplace, as the risk assessment will need updating.


Employers should monitor the health and safety procedures that they have outlined after a COSHH assessment is complete to make sure that they are adequate, and be sure to update the assessment if it is decided that further action is needed. Whilst employers are only legally required to keep a copy of the assessment if they have 5 or more employees, it is recommended that all workplaces have a written copy of their health and safety measures so that everyone knows how risk is being reduced when it comes to hazardous substances. 

A COSHH risk assessment is a vital part of working with hazardous chemicals, and whilst it can be time-consuming to complete, the safety measures that it will implement are essential to keeping a workforce and other individuals safe. If you’re looking for online COSHH Training to further your knowledge of this health and safety legislation, you can find our online course here.