Introduction

The Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR) requires employers to assess the risks of fires and explosions that may be caused by dangerous substances in the workplace. These risks must then be eliminated or reduced as far as is reasonably practicable. Refer to HSE Guidance DSEAR in detail.

Typical work activities to which this may apply include:

  • use of flammable solvents in laboratories

  • transporting flammable substances in containers around a workplace

  • use of flammable gases, such as acetylene, for welding

  • handling and storage of flammable wastes such as fuel oils

  • handling, storage and use of gases under pressure

  • handling, storage and use of substances corrosive to metal

Dangerous substances are substances or mixtures of substances (called 'preparations' in DSEAR) that could create risks to people's safety from fires and explosions or similar events, such as 'thermal runaway' from chemical reactions, or which are corrosive to metal. Liquids, gases, vapours and dusts that may be found in a workplace can all be dangerous substances. Examples include:

  • Solvents, such as acetone, toluene, diethyl ether

  • Paints and varnishes

  • Flammable gases such as acetylene, hydrogen, propane

  • Liquefied petroleum gas (LPG)

  • Dusts from machining and sanding operations

An explosive atmosphere is a mixture of a dangerous substance or substances (gas, mist, dust or vapour) with the air, which has the potential to catch fire or explode. In addition to fire and explosion events, DSEAR also applies to “other energetic events” such as runaway exothermic reactions or decompositions of unstable substances, e.g. decomposition of peroxides.

Process for Controlling Fire and Explosion Risks

Refer to HSE Documents for guidance:

Dangerous Substances and Explosive Atmospheres Regulations 2002. Approved Code of Practice and guidance L138 HSE Guidance Controlling Fire and Explosion risk in the workplace

  1. Identify fire and explosion hazards for work areas within department control. This includes:
  • dangerous substances present including those formed in the workplace

  • potential ignition sources

  • work activities involving the dangerous substance

  • possible formation and extent of explosive atmospheres

  • scale of anticipated event

  1. Assess the risks associated with identified fire and explosion hazards. Carry out a risk assessment using the DSEAR template taking into consideration:
  • work processes and substances used and their possible interactions

  • amount of substance involved

  • risks presented by using more than one dangerous substance in combination

  • arrangements for safe handling, storage and transport of dangerous substances

  1. Eliminate or reduce the risks where reasonably practicable; apply hierarchical approach:
  • Replace with another substance (not classed as dangerous)

  • Use a different work process where the risk of fire or explosion is inherently reduced

  • Substitute for a less dangerous substance, e.g. one with a higher flashpoint

  1. Implement control measures to prevent fire, explosion or similar energetic event. These should be prioritised as follows:
  • reduce the quantity of dangerous substances to a minimum

  • avoid or minimise releases of dangerous substances

  • control releases of dangerous substances at source

  • prevent the formation of an explosive atmosphere, including by ventilation

  • collect, contain and remove any releases to a safe place

  • avoid ignition sources

  • avoid adverse conditions (such as exceeding pressure/temperature limits) that could lead to danger

  • keep incompatible substances apart

  1. Implement mitigation measures to reduce the detrimental effects of a fire, explosion or similar incident as follows:
  • reduce the number of employees exposed to the risk

  • provide plant that is explosion resistant

  • provide explosion suppression or explosion relief equipment

  • take measures to control or minimise the spread of fires or explosions

  • provide suitable personal protective equipment (PPE)

  1. Put in place appropriate arrangements to prepare for accidents, incidents and emergencies. Consider:
  • need for any additional first aid facilities

  • additional safety drills required and tested

  • provision of warning signs and other appropriate communication systems such as alarms, warning lights or tannoy systems

  • provision of any equipment or clothing for persons dealing with an incident