COSHH FAQ's

Some of the most Frequently Asked Questions put to us regarding COSHH. Click a question below to get the answer.

COSHH stands for Control of Substances Hazardous to Health and details how employers must protect their workers from substances that are can damage their health. You can prevent or reduce workers exposure to hazardous substances by:

  • finding out what the health hazards are
  • deciding how to prevent harm to health - (via a risk assessment)
  • providing control measures to reduce harm to health
  • making sure they are used
  • keeping all control measures in good working order
  • providing information, instruction and training for employees and others
  • providing monitoring and health surveillance in appropriate cases
  • planning for emergencies

Most businesses use harmful substances or products that are mixtures of different harmful substances. Some processes create harmful substances. These all can pose a risk to damage employees health, contractors, the public and the environment.

Sometimes substances are easily recognised as harmful. Common substances such as paint, bleach or dust from natural materials may also be harmful. COSHH is a vital part of Health and Safety at Work and is a legal requirement. COSHH makes sure things are done to reduce pain and suffering caused by ill health.

Good, well conducted Risk Assessments, motivated by a constructive desire to know what is going on and the best ways of dealing with problems, can be used not only for reference but also as a plan for identifying action to reduce ill health and thus ensure you and your employees are protected.

For more information on COSHH you can download the HSE publication INDG136: Working with Substances Hazardous to Health


Substances hazardous to health are defined under COSHH as those that are: 'Very Toxic, Toxic, Corrosive, Harmful or Irritant'. They include all substances allocated a Workplace Exposure Limit (WEL) in HSE Publication EH40.

Substantial quantities of these substances (including dust and biological agents) that are found within the work place can be harmful to human health by being either:

  • Inhaled
  • Swallowed (either directly or from settling on food etc or from eating food with contaminated fingers)
  • Absorbed or introduced through the skin or via the eyes (either directly or from contact with contaminated surfaces or clothing)
  • Injected into the body by high pressure equipment or contaminated sharp objects

They can be recognised through knowledge of the process and from previous experience, or by reading HSE guidance notes and relevant trade association's scientific and technical literature such as Material Safety Data Sheets (MSDS).

You could also look at the Health and Safety Executive' website as they have a whole range of resources and publications. Also consider the advice of trade associations, other employers or a competent toxicology, occupational hygiene or health adviser.

  • Is the substance listed in HSE’s publication, EH40 Occupational exposure limits, which lists substances which have been assigned occupational exposure limits?
  • Is the substance a carcinogen or mutagen (see the definition in regulation 2 and the lists in Schedule 1 to COSHH)?
  • Is the substance classified as very toxic, toxic, harmful, sensitising, corrosive, irritant or toxic to reproduction (see the information provided by suppliers, eg the safety data sheet or the package label)?
  • Is the substance a cause of occupational asthma (does the safety data sheet or package label include R42 ‘May cause sensitisation by inhalation’ or R42/43 ‘May cause sensitisation by inhalation and skin contact)?

Carrying out a COSHH assessment can seem quite daunting - especially f you have a lot of processes. But a lot if it comes down to common sense, understanding your processes and materials properly and going through it step by step.

The HSE website has a wide range of resources, guides and publications available for free that will help you ensure you carry out the COSHH Assessment properly. The HSE Publication HSG97: A Step by Step Guide to COSHH is free to download and is a great help.

You need to consider:

  • Identifying the Hazards: Which materials are harmful? How are they Harmful? What processes are they involved in?
  • Whom might be harmed and how? How might workers be exposed? For example Can the substance be breathed in, adsorbed or ingested?
  • How often do people work with the substance and for how long?
  • Is there any one else whom could be exposed? Think about the general public, contractors, visitors, the environment
  • Evaluate the risks. Do you really need to use a particular substance; or is a safer product available?
  • Can you change the process to eliminate the risk? If not you must put in control measures
  • Look at the entire system of work for where control measure might be needed
  • Identify which control measures - such as extraction - are needed and where

For more advice contact the Health and Safety Executive.


Yes - if you have five or more employees you must record the findings of the assessment. If you have fewer than five employees, you are not legally required to record your findings.

However, be aware, the Health and Safety Executive (HSE) strongly advise you to record your assessment as a matter of good practice.

You should ensure you record sufficient information (more is better) to include at least the most significant and appropriate items from the list provided in the COSHH Approved COde or Practice (ACOP) - see the HSE website for more details.

Be sure to show how decisions about risks and precautions have been arrived at. In particular, be aware, many of the requirements of COSHH are subject to the criteria of "where reasonable practicable".

If you decide controls beyond the basic PPE is not practical, you will need to ensure you properly explain and justify your decision not to use further control measures - such as extraction.


Ensuring your staff are not only aware of the dangers of the substances they are using but also how to properly adhere to the working/ handling policies and how to propely use the control measures is vital to ensuring the processes are effective.

With out competent and informed employees the control measures will be virtually useless and continue to expose employees and other to the dangers.

A properly informed and trained work force will also be able to COSHH actions on its own initiative. Employees can also be held accountable to ensure they follow all of their responsibilities under COSHH and adhere to the controls and policies. The employer legally has to inform them of how to do this.

Properly trained staff can also remove some of the supervisor elements from higher tier management.

COSHH requires employees know:

  • The names of the substances to which they are liable to exposed and the risks that exposure poses
  • Any relevant occupational exposure standard, maximum exposure limit or similar self-imposed (in house) work standard that applies to the substance
  • The information on any safety data sheet that relates to the substance and the significant findings of the risk assessment
  • The Precautions they should take to protect themselves and their fellow employees
  • The results of any monitoring of exposure - especially if these exceed the Maximum Exposure Limit
  • The collective results of any Health Surveillance

In many cases monitoring substances that have been identified as hazardous will be required. Under COSHH REgulation 10 your are legally required to monitor hazardous substances and employees exposure - even if there are control measures in place

Monitoring is important:

  • To detect failure or defectiveness of any control measures in place
  • When measurement is required to ensure that Maximum Exposure Limit (MEL) or Workplace Exposure Limit (WEL) is being adhered to and not exceeded
  • As part of a scheduled maintenance routines and additional check to ensure control measures are working within acceptable tolerances
  • To ensure any changes to the process, substance or control measures do not expose employees to the hazards

Monitoring should always be carried out with a clear objective and shouldn't be done for its own sake. Numbers on their own contribute little to managing the hazardous substance and always need to be in context

When monitoring ensure you have relevant bench marks to work from. Establish what the safe parameters are and what constitutes a dangerous situation and make sure you have procedures in place in case those thresholds are crossed and the employees risk harmful exposure