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Knowledge Base » Health and Safety » How to undertake a COSHH Assessment

How to undertake a COSHH Assessment

Last updated on 30th March 2023

For many UK employers, COSHH risk assessments are a legal requirement for employee safety. Official figures reveal that roughly 200 workers in the UK die as a result of a workplace injury every year. That said, it’s believed that up to 20,000 UK workers may lose their life prematurely due to occupational diseases.

There are many risks present across multiple industries, with exposure to chemicals and fumes contributing to a range of debilitating conditions. This is especially true when people are exposed repeatedly over time.

If you’re an employer, you have a legal duty to promote safety in the workplace and reduce any risks to the health of all your employees. Part of your responsibility requires undertaking a COSHH assessment if there are any hazardous substances present on your work premises.

If your industry uses hazardous substances, you are likely to be familiar with COSHH regulations. However, it can be challenging to identify all hazardous substances. Therefore, you must identify and assess all potential risks in your workplace, as you may be unaware of some critical duties that fall under COSHH assessments.

This post will explain precisely what COSHH is, what your legal responsibilities are as an employer and the five steps of a COSHH assessment. We’ll also discuss why you need to allocate a competent person within your organisation to undertake your COSHH assessment, and what their responsibilities should be.

We’ll describe how a member of your team must collect information on hazardous substances in your workplace and identify the risks that hazardous substances pose to staff. We’ll also look at how you should select and implement appropriate control measures, record your findings, and monitor your performance throughout the COSHH assessment process.

What is COSHH?

COSHH stands for the Control of Substances Hazardous to Health. COSHH assessments are health and safety documents produced by a designated ‘competent’ member of staff. These documents are created to monitor the production or use of hazardous substances within your work environment.

A COSHH risk assessment is a legal requirement under COSHH regulations in the UK. Such assessments must be carried out throughout your workplace to assess any risks that are associated with hazardous substances on your premises.

From schools through to care homes, every business that houses and/or uses potentially hazardous substances must undertake a thorough COSHH risk assessment to protect their staff.

A broad range of hazardous substances require a COSHH assessment. This includes dust, chemicals, fumes, mixtures, biological agents, and any substance that could pose a risk to health due to the way that it’s used or its properties.

COSHH covers:

  • Chemicals.
  • Products containing chemicals.
  • Fumes.
  • Dusts.
  • Vapours.
  • Mists.
  • Nanotechnology.
  • Gases and asphyxiating gases.
  • Biological agents (germs). If the packaging contains any hazard symbols, then it’s classed as a hazardous substance.
  • Germs that cause diseases such as legionnaires disease or leptospirosis, or germs used in laboratories.

As UK employers, you have a duty under the Control of Substances Hazardous to Health Regulations 2002 to protect your staff from exposure. This means that you must assess any risks associated with the use of solvents, chemicals, and other potentially harmful agents. It would help if you took every available precaution to prevent employee exposure to these risks.

Stock pile of cleaning supplies that are hazardous stored safely

What are employer responsibilities?

Under COSHH regulations, employers have many responsibilities, including:

1. Identifying and implementing control measures to protect your staff from hazardous substances.
2. Adequately controlling or preventing any exposure to hazardous substances across all work premises.
3. Providing employees with training, instructions, information, and Personal Protective Equipment (PPE) wherever necessary.
4. Making sure that all control measures are fully maintained, in clean condition, and full working order wherever appropriate.
5. Creating procedures and plans to deal with any accidents and emergencies that involve hazardous substances in your workplace.
6. Ensuring that any employee that is exposed to hazardous substances while working is under appropriate health surveillance.
7. Making sure that all substances are kept below the Workplace Exposure Limit (WEL).

Workplaces with more significant risks to exposure, such as school chemistry labs and hairdressers, require more specific action and investigation than standard offices. However, as an employer, you have a legal obligation to assess any risks posed by hazardous substances, regardless of where you work.

Once assessed and identified, action can be taken to reduce the risks to a bare minimum, ensuring that safety comes first for your workforce.

What is a COSHH assessment?

COSHH assessments are systematic examinations of tasks or processes in your workplace that involve the use of potentially hazardous substances. COSHH assessments are carried out so that all the hazardous substances your staff may use are identified. They also help to decide whether your safety precautions are acceptable and what control measures are currently in place.

In practical terms, COSHH risk assessments provide thorough insights into your workplace and the products, processes, and situations that could cause harm to your staff. Once these have been identified, you can evaluate how severe and likely the risks are, before deciding what measures must be put in place to prevent harm from occurring.

These measures could include eliminating exposure by using non-hazardous alternatives, or ensuring that all exposure is below the Workplace Exposure Limit. Although not a legal requirement of your COSHH assessment, the environmental impact of the disposal or use of chemicals should also be taken into consideration.

When evaluating risks for COSHH, you must ask questions such as:

– Is this activity safe to operate?

– Does it need improved control measures? (Such as ventilation or PPE).

– Is this risk significant enough to my employees’ health to warrant special containment?

The steps to a COSHH assessment

There are five steps to a COSHH assessment:

1. Collect information about the substances used in your workplace and your work practices.
2. Evaluate the health risks related to these substances and practices.
3. Choose appropriate control measures that will reduce or eliminate these risks.
4. Implement control measures and record your findings.
5. Monitor performance across all areas and review your COSHH assessment.

We will now break down each of these steps in more detail so that this piece can be used as a point of reference as you begin your COSHH risk assessment.

1. Collect information about the substances used in your workplace and your work practices

COSHH covers any substances that pose a potential health risk, including:

  • Chemicals.
  • Products that contain chemicals.
  • Vapours, mists, dust, and fumes.
  • Gases and asphyxiating gases.
  • Eggs, larvae, and other microorganisms.

You may be unaware of some of the hazardous substances within your workplace. This is because not every hazardous substance is labelled with the appropriate hazard warning symbols. Things like wet cement, glue, fungi, flowers, and some bulbs are all classed as potentially hazardous substances under COSHH guidelines.

Additionally, for those of you that work in manufacturing, intermediates, bi-products, and finished products must be considered across all of your working processes. This is because these processes could be classed as hazardous.

To identify any hazardous substances in your workplace, you must:

  • Inspect your workplace thoroughly, looking for any signs of exposure to hazardous substances.
  • If you’re unsure about any substances, check with the product manufacturers, consult your industry HSE page, ask a specialist, or look at the EH40 Occupational Exposure Limits List.
  • List all work processes and jobs that involve exposure.
  • Review your accident book.

It would be best if you considered why the substances are hazardous, identify how exposure occurs, and decide what effects this exposure may have on members of your team. For example, a gas may be inhaled, a liquid could become exposed via a contaminated sharp, or certain products may irritate the skin if accidentally spilt.

Identifying people who are or could be exposed:

One way of discovering who are/could be exposed is by investigating each working activity in turn and listing all the exposures for each one.

The various people that could be exposed include:

  • Contractors.
  • Employees.
  • Site visitors.
  • Managers and supervisors.
  • Maintenance and cleaning staff.
  • People living or working nearby.
  • Office workers.

If you require examples regarding how work processes could affect various groups of people, HSE’s official guide will help you gain more understanding.

COSHH doesn’t cover asbestos, radioactive substances, or lead, as each of these substances has specific regulations in place.

For additional information concerning substances that are not covered by COSHH, visit the official HSE website.

2. Evaluate the health risks related to these substances and practices.

When considering health risks, you must evaluate:

  • How likely exposure could be.
  • The potential that a substance has to cause harm.
  • The duration and level of exposure.
  • How often exposure could occur in your workplace.

As you start to assess exposure, consider potential spillages, day-to-day tasks, the maintenance and cleaning schedule, and any situations that could expose your staff to hazards as they do their job. Once the exposure has been evaluated, you must next consider the point at which such exposure could become a health risk.

Accidents and risks to health can occur when exposure:

  • Could have been reasonably prevented.
  • Is controlled in a manner that fails to comply with COSHH Regulation 7.
Worker completing a COSHH risk assessment

3. Choose appropriate control measures that will reduce or eliminate these risks

At this stage of your COSHH risk assessment, you have successfully identified the hazards, decided which members of your staff are at risk, evaluated the risks posed to staff and visitors, and noted any instances of unacceptable exposure.

Now, you must decide how these risks can be reduced or eliminated. Note that it’s almost impossible to eliminate or reduce all risks straight away. Therefore, we recommend that you prioritise certain hazards.

Start this process by considering:

  • Which hazards carry the most severe risks to health?
  • How fast and efficiently can you start to implement levels of control?
  • What hazards harbour the most immediate risks?

The hazards that pose the most health risks should be tackled first. These shouldn’t be ignored as your team fixes problems that are quick and easy to solve.

When deciding how to control a COSHH hazard, it helps to implement the hierarchy of control:

1. Elimination – Give careful consideration to your systems and processes until you can eliminate the exposure to hazardous substances on your premises.

2. Substitution – Find non-hazardous alternatives to substitute any hazardous substances in use (if applicable).

3. Isolation – Consider providing special equipment that encloses any hazardous processes to limit exposure.

4. Engineering – This step involves making physical changes to your work processes to reduce or remove risk. This could include adding splash guards to equipment or providing ventilation to an enclosed area.

5. Administration – Rotate shifts, make sure your staff are trained appropriately and install signs to use administration as a way of eliminating risk.

6. Personal Protective Equipment (PPE) – Provide PPE, such as face masks and gloves for staff that are at a high risk of exposure to hazards.

4. Implement control measures and record your findings

It’s a legal requirement for you to record all COSHH risk assessment results if you employ five or more staff. That said, we recommend that all businesses record their findings as a way of being accountable for the changes that they implement. Such records should list hazards identified, precautions put in place, and why these precautions were implemented.

5. Monitor performance across all areas and review your COSHH assessment

To confirm that your control measures are effective and test their longevity, your COSHH assessment should be regularly monitored.

It’s unnecessary to repeat the entire COSHH assessment process each time your assessment is reviewed. Instead, the current version should be revised, tweaking and updating things whenever appropriate.

Note, your COSHH assessment must be immediately reviewed if:

  • Evidence suggests your existing assessment is invalid. For example, if an accident happens that could have been prevented.
  • Work circumstances such as premises, equipment, processes, or substances change.
COSHH chemical cleaning supply stored safely in cleaning cupboard

Who will carry out the COSHH assessment?

The Approved Code to Regulation 6 states:

“Employers must ensure that whoever carries out the assessment and provides information on the prevention and control measures is competent to do so.”

Regulation 12 of the COSHH framework requires employers to make sure any person (either as a direct employee or otherwise) who undertakes work under COSHH has sufficient and suitable information, training, and instruction.

Therefore, as an employer, you must ensure any staff that work on your COSHH risk assessment are adequately trained so that they can assess risks without posing further harm to employees.

To be seen as competent, any person nominated to undertake a COSHH assessment must:

  • Know how the work activity creates, produces, or uses substances that are hazardous to health.
  • Have training, skills, knowledge, and experience so that they can make clear decisions regarding the level of risk and the measures needed to control exposure adequately.
  • Be able, and authorised by their employer, to collate any necessary, relevant information.

Under the Regulation 7 requirements of the Management of Health and Safety Work Regulations 1999 (MHSWR), such competency should be available in-house. Therefore, all suitable employees should be provided with the proper instructions, information, and training to give them the expertise required to safely and effectively complete a COSHH assessment.

COSHH guidance recognises that, occasionally, external help is required. If this is the case, you, as an employer, must ensure that anyone involved in your COSHH assessment is fully capable of completing the task. To do this, you may provide specific information about your work circumstances, including any hazardous substances on the premises, and their hazardous properties.


COSHH was introduced as a legal framework to protect workers against exposure to hazardous substances. COSHH assessments place a duty on UK employers to assess any risks of exposure to substances that are hazardous to health and guarantee that the employees’ health and safety are protected at all times in the workplace.

If COSHH is poorly managed, your employees could suffer the potentially dangerous effects of hazardous substances, which can prove fatal. Improper COSHH assessments can cause loss of productivity in the workplace, leave you facing prosecution, and could lead to civil claims from your staff.

However, if you follow regulations and manage COSHH assessments carefully and professionally, workplace conditions will improve for all staff, reducing any time lost due to ill health, and mitigating the risk of litigation.

After conducting a thorough COSHH assessment, you will identify hazardous substances that may have previously gone unnoticed, and you’ll understand why they are hazardous.

This will help to ensure that no member of staff is unknowingly exposed to hazardous substances while completing their work. Ultimately, COSHH will give you and your team peace of mind, as your assessments rigorously improve workplace safety.

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About the author

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Marcel Deer

Marcel qualified as a journalist from Liverpool John Moore's University in 2009. After working in PR and digital marketing for five years, he spent two years working as a social media consultant. Since then, he's worked from 15 countries as a remote content writing/marketing expert.

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