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COSHH covers hazardous substances, such as those that are toxic or are irritants, but does not assess sufficiently those materials which also possess flammable or explosive properties, these being described as dangerous substance. Dangerous substances include all materials that are explosive, oxidising, extremely flammable, highly flammable, or flammable. Examples of such materials are chemical reagents, as well as solvents, paints, and varnishes, flammable liquids and gases, and dusts from various operations (such as machining and sanding), or produced in handling other materials (such as foodstuffs).



DSEAR requires employers to:

  • Assess the risks

  • Adopt control measures

  • Mitigate the severity of any incident

  • Plan for emergencies

  • Inform, instruct and train employees

Ultimately, an employer has a responsibility under DSEAR to protect employees and other people such as visitors to site or premises, including the public, from risks associated with dangerous substances.

Limiting the effects of any incident, should one occur, can be achieved through any of the following.

  • By reducing the number of employees exposed to the risk

  • By providing plant that is explosion resistant

  • By using explosion suppression or explosion relief equipment

  • By taking measures to control or minimise the spread of fires or explosions

  • By providing suitable personal protective equipment

The steps taken to minimise the limits of an incident should, again, be appropriate to the nature of the process and consistent with the severity of any risk.



Assessing the risks means:

  • Identifying dangerous substances in the workplace

  • Identifying processes in which dangerous substances are used

  • Assessing the risks of fires and explosions that may be caused by using dangerous substances in the workplace

If there is no risk to safety from fires or explosions, or the risk is determined to be trivial, no further action is needed under DSEAR.


Ideally, steps should be taken to completely eliminate the risk, for example by substituting a safer substance (one that is not so dangerous) or by modifying the process. However, this is not always possible. Where it is not possible to completely eliminate the risk, employers must take measures to control the risks and mitigate (reduce the severity of) the effects of any fire or explosion.

Control measures should be applied in the following order:

  • Reduce the quantity of dangerous substances to a minimum

Highest Priority

  • Avoid or minimise releases of dangerous substances

  • Control releases of dangerous substances at source

  • Prevent the formation of a dangerous atmosphere

  • Collect, contain and remove any releases to a safe place (for example, through ventilation)

  • Avoid ignition sources

  • Avoid adverse conditions (for example, exceeding the limits of temperature or control settings) that could lead to danger

  • Keep incompatible substances apart

Lowest Priority

The control measures should be appropriate to the nature of the process and consistent with the severity of any risk.

The employer must develop plans and procedures to meet any emergency that arises through the use of dangerous substances. This could, if appropriate, include consultation with the safety services, and the Health and safety Executive. These arrangements should be proportionate to the nature of the risk, but could include:

  • Training in evacuation procedures

  • Training in fire fighting procedures

  • Use of warning or alarm systems

  • Use of robust methods of communication

If assessment indicates that plans and procedures need to be developed, these must be made available to the emergency services to allow them to comment on them, and to develop their own, if necessary.


Employers have a responsibility to provide employees with relevant information, instructions or training about dangerous substances in the workplace before the process which uses them is allowed to commence. Such advice should include details about:

  • The presence and properties of dangerous substances

  • Storage and transport of the dangerous substances

  • The process and the risks associated with it

  • Sources of information such as MSDS

  • Legislation applying to the substances and process

  • The findings of any risk assessments (also COSHH)

  • How to use control measures and about their maintenance

  • Procedures to follow in case of emergency

Contractors and other visitors to site should also be given approriate safety advice if involved in the use of the dangerous substances.

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