Read the full text: Dangerous Substances and Explosive Atmospheres Regulations 2002 on legislation.gov.uk.
DSEAR — the Dangerous Substances and Explosive Atmospheres Regulations 2002, SI 2002/2776 — requires employers to assess and control the risk of fire, explosion and similar energetic events arising from dangerous substances at work. It covers flammable liquids and gases, combustible dusts that can form an explosive cloud in air, and substances that are explosive, oxidising, or otherwise capable of producing a dangerous atmosphere.
It is made under the Health and Safety at Work etc. Act 1974 and enforced by the Health and Safety Executive (HSE). It applies wherever a dangerous substance is or could be present at a workplace — from a small workshop using solvents to a bakery generating flour dust to a site storing LPG cylinders.
What Counts as a Dangerous Substance?
The definition is broad and centres on the potential to cause harm through fire, explosion or a similarly energetic event — not on general toxicity, which is COSHH territory instead. In practice this covers: flammable liquids such as solvents, fuels, thinners, and many cleaning and adhesive products; flammable gases such as LPG and acetylene; combustible dusts that can form an explosive atmosphere when suspended in air, including flour, wood dust, sugar dust and some metal dusts; and substances classified as explosive or oxidising. The definition extends to any dust, vapour or mist the substance can give off, not just the substance in its stored or supplied form.
Risk Assessment
Regulation 5 requires a suitable and sufficient assessment of the risks to employees wherever a dangerous substance is or is liable to be present. It must specifically consider: the hazardous properties of the substance and any supplier safety data; the work processes, quantities involved, and the risk where more than one dangerous substance is present in combination; arrangements for safe handling, storage and transport; activities such as maintenance where risk can spike; how likely an explosive atmosphere is to occur and how long it would persist; how likely ignition sources (including static electricity) are to be present; and the scale of the anticipated effects of a fire or explosion. The assessment must be reviewed regularly and whenever there's reason to think it's no longer valid or the work has changed significantly. No new work activity involving a dangerous substance can start until the assessment is done and the required measures are in place. Employers with 5 or more employees must record the significant findings in writing.
The Control Hierarchy
Regulation 6 sets a strict order of priority, and it isn't optional to skip straight to personal protective equipment. Substitution comes first — avoiding the dangerous substance altogether by replacing it with something safer, so far as reasonably practicable. Where elimination isn't possible, measures must be applied in this order: reduce the quantity present to a minimum; avoid or minimise release; control release at source; prevent an explosive atmosphere forming, including through ventilation; ensure any release that does happen is safely collected, contained or removed; avoid ignition sources and adverse conditions that could trigger harmful effects; and segregate incompatible substances. Only after that does the regulation turn to mitigating the effects of a fire or explosion that does happen — minimising the number of people exposed, avoiding fire or explosion spreading, explosion relief and suppression equipment, plant built to withstand explosion pressure, and suitable PPE as a last line of defence.
Zoning — Classifying Hazardous Areas
Where an explosive atmosphere may occur, Regulation 7 requires the employer to classify those places into zones based on how often and for how long the atmosphere is likely to be present. Gas and vapour atmospheres use Zones 0, 1 and 2; dust atmospheres use Zones 20, 21 and 22 — in each case, the lower the number, the more frequent or persistent the hazard. Equipment and protective systems used in a classified zone must meet specific requirements suited to that zone. Zones must be marked with warning signs at their points of entry where necessary, and before a workplace containing hazardous zones is used for the first time, its overall explosion safety must be verified by someone competent in explosion protection. Workers in these areas must be provided with work clothing that doesn't generate electrostatic discharges.
Emergency Arrangements
Regulation 8 requires procedures for accidents, incidents and emergencies related to dangerous substances — first-aid facilities, regularly tested safety drills, suitable warning and communication systems, and, before explosive conditions are reached, visual or audible warnings with employees withdrawn where necessary. Escape facilities must be provided where the risk assessment shows they're needed. Relevant information must be made available to the emergency services and, unless the risk assessment shows it's unnecessary, displayed at the workplace. If an incident does happen, only people essential to repairs or remedial work are allowed in the affected area, and they must have appropriate PPE and any specialised safety equipment needed. This whole set of duties doesn't apply where the risk assessment shows the quantity of substance involved presents only a slight risk and the general control measures already required under Regulation 6 are sufficient to control it — a genuine proportionality built into the regulation, not a loophole around the risk assessment duty itself.
How DSEAR Relates to COSHH
The two regulations frequently apply to the same substance but address different harms. COSHH covers harm to health from exposure — breathing in vapour, skin contact, ingestion. DSEAR covers the risk of fire, explosion and similar energetic events from the same substance's physical properties. A solvent used for cleaning parts is a good example: it needs a COSHH assessment for the health risk from inhaling the vapour, and a separate DSEAR assessment for the fire and explosion risk from its flammability. Many workplaces need both, covering the same substance from two different angles.
Penalties for Non-Compliance
DSEAR doesn't set out its own offences and penalties — like most HSE-enforced regulations, breaches are prosecuted under Section 33 of the Health and Safety at Work etc. Act 1974: a fine and/or up to 6 months' imprisonment on summary conviction, or an unlimited fine and/or imprisonment on indictment in the Crown Court. The HSE treats fire and explosion incidents as high-severity events, and inadequate DSEAR risk assessment or zoning is a recurring finding in investigations following serious workplace fires and explosions.
How This Relates to Risk Assessments
The DSEAR risk assessment is a specific, substance-focused assessment sitting alongside the general risk assessment duty every employer has under the Management of Health and Safety at Work Regulations 1999. Where dangerous substances are genuinely present, DSEAR's specific requirements (substance properties, ignition sources, zoning, emergency arrangements) go well beyond what a generic workplace risk assessment would cover, and the two need to work together rather than one substituting for the other. Anyrisks can generate the general workplace risk assessment covering a site or activity where dangerous substances are one of several hazards — for example a construction risk assessment covering fuel storage or hot works — but a DSEAR-specific zoning assessment for a genuinely hazardous process needs specialist input from someone competent in explosion protection.
A Worked Example
A small joinery workshop generates wood dust from sanding and cutting. The employer assesses the risk under DSEAR: wood dust can form an explosive cloud if it accumulates and becomes airborne in sufficient concentration, and there are potential ignition sources from electrical equipment and sparks from cutting tools. Following the control hierarchy, the workshop installs local extraction at each machine to control dust at source, uses appropriately rated electrical equipment near dust-generating processes, and has a housekeeping routine to prevent dust accumulating on surfaces where it could later become airborne. The area immediately around the extraction outlet is classified as a Zone 22 (occasional dust atmosphere) and marked accordingly. The risk assessment is recorded in writing, since the workshop employs more than 5 people, and reviewed whenever equipment or the process changes.
