COSHH (Control of Substances Hazardous to Health) Toolbox Talk

Glass tubes containing different coloured chemicals.Reason: Hazardous substances can be used in, or created by, work processes.

Why is it important: Ignore a hazardous substance today and you may wish you hadn’t by tomorrow. Most businesses use substances or products that are mixtures of substances. Some processes create substances. These could cause harm to employees, contractors and other people.
Sometimes substances are easily recognised as harmful. Common substances such as paint, bleach or dust from natural materials may also be harmful.

Outline: This talk will cover: COSHH assessment, hazards, control measures and safe use of substances.

What is a COSHH Assessment?

  •  A COSHH assessment concentrates on the hazards and risks from substances in your workplace.
  • Management must carry out a CoSHH assessment to find out whether:
  • Exposure to a substance can be eliminated.
  • Alternative work methods can be used to try and reduce exposure.
  • A less hazardous substance can be used.
  • Any substance with a hazard warning label has the potential to cause harm – assess the risk before using it.
  • Your employer has a legal duty to assess the risk involved in working with a hazardous substance, decide what precautions should be taken o deal with the risk and to instruct you on what precautions must be taken.
  • Make sure you understand these instructions before you work with any hazardous substance, get the COSHH assessment.

What is a Hazardous Substance?

  • Any preparation (mixture) that is dangerous for supply, and for which an indication of danger specified for the substance is very toxic, toxic, harmful, corrosive or irritant.
    • Any substance which has a Workplace Exposure Limit (WEL).
    • Any biological agents used at work.
    • Any dust other than one with a WEL at a concentration in air above 10 mg/m3 averaged over 8 hours, or any such respirable dust above 4 mg/m3 over 8 hours.
    • Any other substance that creates a risk to health because of its properties and the way it is used or is present in the workplace.

How Could You Be Affected By a Hazardous Substance? Ingestion, Inhalation, Absorption

Examples of Hazardous Substances on Construction Sites

Cement flowing down a chute.

  • Contaminated ground
  • Concrete ad-mixtures
  • Cement
  • Hard wood dust
  • Resins
  • Epoxy-based paints
  • Welding fumes
  • Asbestos


Don’t mix chemicals or substances unless they are specifically intended to be mixed together, such as some adhesives.

Control Measures

  • When using hazardous substances, wear the correct PPE and know how to look after and use it correctly.
  • Know where washing and first-aid facilities are on site.
  • Ensure hazardous substances are put back into secure location after use and not left out on site.
  • Provide control measures to reduce harm to health e.g. extraction.
  • Provide information, instruction and training for employees and others.
  • Provide monitoring and health surveillance in appropriate cases.
  • Plan for emergencies.

Using substances mindmap


  • Some chemicals can become unstable when old and explosions can result if these are mishandled. Check the condition of all containers for indications of leaks, swelling or age (rust).
  • Store in accordance with packaging instructions.
  • Some chemicals must be stored next to others – check the label.

If you have any questions about the contents of this Toolbox Talk, do not hesitate to contact us – our team would be happy to help you with any queries. Find more Toolbox Talks here.

Need further training? Check out our Control of Hazardous Substances Training Course!