Safety Services


What are hazardous chemicals​?

For a chemical to be hazardous it needs to have a known negative effect on the health of people or the environment.

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What is a hazardous chemical?

A hazardous chemical is a substance or mixture that may pose harm to human health, facilities/property, and the environment. It will have one or more of the following characteristics:

  • Irritant
  • Corrosive
  • Harmful to health
  • Toxic or very toxic
  • Flammable / explosive
  • Reactive with in standard lab conditions (reacts with water, oxygen, changes in temperature etc)
  • Oxidiser (reactive with other chemicals)
  • Hazardous to the environment
  • Compressed gas

Chemical substances exist as solids, liquids, vapours, gases or fumes, and may change between these phases of matter with changes in temperature or pressure​.

The rules for ensuring that hazardous chemicals are used safely are covered in the Control of Substances Hazardous to Health (COSHH) Regulations 2002.

​Control of Substances Hazardous to Health Regulations 2002 (COSHH)

COSHH is the law that requires all employers including UCL to have effective control over chemicals that are hazardous to health.​

Effective control is defined as:​

  1. The principles of good practice for control are being applied and implemented.​

  2. Any workplace exposure is not exceeded.​

  3. Exposure is reduced to as low as reasonably practicable (ALARP).​

​Since 2005 COSHH has given a checklist of controls that should be in place when working with hazardous chemicals. This is not a hierarchal list, all controls should be considered and put in place if possible – it is referred to as the Principles of Good Practice in Control​.

​The way of recording that the Principles of Good Practice in Control have been implemented is a COSHH assessment.​

Principles of Good Practice for Control​

​There are 8 principles of control within COSHH. This is not a hierarchy where the more important one is listed first but rather a framework with all eight principles needing to be adhered to:​

​When working with any hazardous chemicals, the risk assessment should indicate how the eight principals have been met under the control measures to ensure that when the activity is carried out, the risks are adequately controlled.​

1. Design and Operate

Design and operate processes and activities to minimise emission, release and spread of chemicals hazardous to health.​

2. Relevant routes of exposure ​

Take into account all relevant routes of exposure - inhalation, skin absorption and ingestion - when developing control measures.​

3. Control exposure ​

Control exposure by measures that are proportionate to the health risk.​

4. Effective and reliable control ​

Choose the most effective and reliable control options which minimise the escape and spread of chemicals hazardous to health.​

5. PPE​

Where adequate control of exposure cannot be achieved by other means, provide, in combination with other control measures, suitable personal protective equipment.​

6. Check​ and Review

Check and review regularly all elements of control measures for their continuing effectiveness.​

7. Information and Training 

Inform and train all employees on the hazards and risks from the chemicals with which they work and the use of control measures developed to minimise the risks.​

8. Holistic Approach

Ensure that the introduction of control measures does not increase the overall risk to health and safety.​

Last updated: Wednesday, March 31, 2021

Hazardous substances must be risk assessed before use

Some chemicals are non-hazardous substances and can be used without a risk assessment. 

COSHH Assessment →