DSEAR Regulations 2002: UK Guide to Dangerous Substances and Explosive Atmospheres

Last updated: September 2026 · Based on DSEAR 2002 (SI 2002/2776) as amended and HSE L138 (2nd edition)

DSEAR, the Dangerous Substances and Explosive Atmospheres Regulations 2002 (SI 2002/2776), is the Great Britain law that requires employers and the self-employed to control fire, explosion and similar risks from dangerous substances at work. It applies wherever a dangerous substance is, or is liable to be, present at a workplace, from a paint store or a petrol forecourt to a flour mill or a refinery. Employers must assess the risks, eliminate or reduce them, classify places where explosive atmospheres may occur into zones, use suitable equipment in those zones, and prepare for emergencies.

DSEAR was made under the Health and Safety at Work etc. Act 1974 and implements the safety parts of the Chemical Agents Directive 98/24/EC and the ATEX "workplace" Directive 1999/92/EC. It is enforced by HSE and local authorities, and HSE's Approved Code of Practice and guidance L138 (second edition, 2013) explains how to comply. It continued unchanged after Brexit. Northern Ireland has its own equivalent, the Dangerous Substances and Explosive Atmospheres Regulations (Northern Ireland) 2003.

What Is DSEAR?

DSEAR places duties on employers to protect workers and other people from risks arising from fires, explosions and similar energy-releasing events (such as a runaway exothermic reaction) caused by dangerous substances in the workplace. Since June 2015 it also covers substances corrosive to metals and gases under pressure. Under regulation 2, a "dangerous substance" is:

• Any substance or mixture that meets the criteria for classification in a physical hazard class under the CLP Regulation, whether or not it is actually classified. This covers, for example, explosives, flammable gases, aerosols, liquids and solids, oxidizing substances, organic peroxides, self-reactive and pyrophoric substances, gases under pressure and substances corrosive to metals.
• Any substance or mixture that creates a risk because of its physico-chemical or chemical properties and the way it is used or is present at the workplace (for example a high-flash-point liquid handled above its flash point).
• Any dust, whether solid particles or fibers, that can form an explosive mixture with air or an explosive atmosphere.

This scope is deliberately broad. Petrol, LPG, paints, varnishes, solvents, grain dust, wood dust, and even flour are covered. An "explosive atmosphere" under DSEAR is a mixture of air with dangerous substances in the form of gases, vapors, mists or dusts in which, after ignition, combustion spreads to the entire unburned mixture.

Who Does DSEAR Apply To?

• Employers at any workplace in Great Britain where a dangerous substance is or is liable to be present, whatever the size of the business.
• The self-employed, who have the same duties as an employer (regulation 4(2)).
• Written records of the risk assessment are required where the employer has five or more employees (regulation 5(4)); smaller employers still have to carry out the assessment.

Regulation 3 sets exclusions. Normal ship-board work by a ship's crew is outside DSEAR, and the zoning and coordination duties (regulations 5(4)(c), 7 and 11) do not apply to, among others, areas used for medical treatment of patients, domestic-type gas appliances, the manufacture and handling of explosives, and activities at quarries, borehole sites and offshore installations, which have their own legislation.

ATEX Regulations in the UK: DSEAR and UKEX

The EU's two ATEX directives each have a UK counterpart. When people search for "ATEX regulations UK", they usually mean one of these:

Equipment placed on the GB market can carry either the UKCA marking (conformity assessed by a UK Approved Body, known as UKEX certification) or the EU CE marking. The Product Safety and Metrology etc. (Amendment) Regulations 2024, in force from 1 October 2024, allow CE-marked ATEX equipment to be accepted in Great Britain indefinitely. See UKCA Ex (UKEX) certification for the product side.

DSEAR vs ATEX

DSEAR is the UK's implementation of the ATEX workplace directive, so the zoning and equipment rules are the same. The differences are mainly in scope and paperwork:

Important: DSEAR covers more ground in one set of regulations than 1999/92/EC does on its own, because it also carries the safety requirements of the Chemical Agents Directive. EU member states implement those requirements too, often in separate national rules, so the practical duties are similar across Europe. The main paperwork difference is that DSEAR does not require a separate "explosion protection document": L138 notes that the EU requirement is covered in Great Britain by the risk assessment and the measures under regulations 5, 6 and 7.

Employer Duties Under DSEAR

DSEAR imposes a clear hierarchy of duties on employers:

1. Risk Assessment (Regulation 5)

Every employer must carry out a suitable and sufficient assessment of the risks from dangerous substances before any new work involving them starts. Regulation 5(2) requires the assessment to consider:

• The hazardous properties of the substance
• Information on safety provided by the supplier, including the safety data sheet
• The circumstances of the work: the work processes and substances used and their possible interactions, the amount involved, the risk of substances in combination, and arrangements for safe handling, storage and transport (including waste)
• Activities, such as maintenance, where there is potential for a high level of risk
• The effect of the control measures taken or planned
• The likelihood that an explosive atmosphere will occur and its persistence
• The likelihood that ignition sources, including electrostatic discharges, will be present and become active and effective
• The scale of the anticipated effects of a fire or explosion
• Any places connected via openings to places where explosive atmospheres may occur
• Any additional safety information needed to complete the assessment

The assessment must be reviewed regularly, and whenever there is reason to think it is no longer valid or there has been a significant change (regulation 5(3)).

2. Elimination or Reduction of Risk (Regulation 6)

Risk must be eliminated or reduced so far as is reasonably practicable. Substitution comes first; then control and mitigation measures consistent with the risk assessment:

1. Substitution: Replace the dangerous substance with a substance or process that eliminates or reduces the risk
2. Control (in order of priority, regulation 6(4)):
   • Reducing the quantity of dangerous substances to a minimum
   • Avoiding or minimizing releases of dangerous substances
   • Controlling releases at source
   • Preventing the formation of explosive atmospheres, including by appropriate ventilation
   • Collecting, containing, and removing any releases to a safe place, or otherwise rendering them safe
   • Avoiding ignition sources (including electrostatic discharges) and adverse conditions
   • Segregating incompatible dangerous substances
3. Mitigation (regulation 6(5)): reducing the number of employees exposed, preventing fire or explosion spreading, explosion relief, explosion suppression, plant built to withstand the explosion pressure, and suitable personal protective equipment

3. Hazardous Area Classification (Regulation 7)

Where explosive atmospheres may occur, the employer must classify places as hazardous or non-hazardous and classify hazardous places into zones, using Schedule 2 (the same zone definitions as the ATEX Workplace Directive). In practice the method comes from BS EN IEC 60079-10-1 for gases and vapors and BS EN IEC 60079-10-2 for dusts. See Zone Classification for the full zone system. Regulation 7 also requires:

• Warning signs at the entry points to hazardous places where necessary (Schedule 4)
• Verification of the overall explosion safety of the workplace by a competent person before it is used for the first time (regulation 7(4))
• Work clothing that does not give rise to electrostatic discharges in hazardous places (regulation 7(5))

4. Equipment Selection

Equipment and protective systems in hazardous places must be selected on the basis of the Equipment and Protective Systems Regulations 2016 unless the risk assessment finds otherwise (Schedule 3), using the equipment categories:

Equipment already in use at the workplace on or before 30 June 2003 is exempt from Schedule 3 (regulation 17(1)); HSE's guidance is that it can continue in use provided the risk assessment shows it is safe. Installation, inspection and maintenance normally follow BS EN IEC 60079-14 and BS EN IEC 60079-17 (see Installation & Inspection).

5. Recording the Findings (Regulation 5(4))

Employers with five or more employees must record the significant findings of the risk assessment. The record must include in particular:

• The measures taken or to be taken to comply with DSEAR
• Enough information to show that the workplace and work processes are designed, operated and maintained with due regard for safety, and that work equipment is used safely
• Where an explosive atmosphere may occur: the places classified into zones, the equipment needed for safe operation in those places, confirmation that the explosion-safety verification under regulation 7(4) has been done, and the aim and measures of any coordination between employers

This record does the job of the EU "explosion protection document". Many duty holders still call it an EPD, which is fine as long as it contains the items above.

6. Emergencies, Training, Labeling and Coordination (Regulations 8 to 11)

• Regulation 8: arrangements to deal with accidents, incidents and emergencies: procedures and regularly tested safety drills, first aid, warning and communication systems, escape facilities where needed, and information for the emergency services
• Regulation 9: information, instruction and training for employees
• Regulation 10: identification of the hazardous contents of containers and pipes
• Regulation 11: coordination between employers sharing a workplace where an explosive atmosphere may occur

DSEAR Assessment Checklist

A practical sequence for a DSEAR assessment, following regulations 5 to 11 and L138:

1. List the dangerous substances: collect safety data sheets, check CLP physical hazard classes, and include substances created by the process (solvent vapor from heating, dust from cutting or sanding, flammable gas from battery charging or reactions).
2. Describe the work: processes, quantities, storage, transfer, waste, and non-routine tasks such as cleaning, maintenance, hot work, start-up and shutdown.
3. Find where releases can occur and whether an explosive atmosphere can form; include places connected by openings, drains and ducts.
4. Classify zones using Schedule 2 and BS EN IEC 60079-10-1 / -10-2, and draw them on a hazardous area drawing.
5. Identify ignition sources: electrical equipment, hot surfaces, mechanical sparks, naked flames and hot work, static electricity (people, containers, powders, flowing liquids), vehicles.
6. Apply the regulation 6 hierarchy: substitute, reduce quantities, contain, ventilate, control ignition sources, then mitigate (relief, suppression, isolation, fewer people exposed).
7. Check equipment against the zones: category and EPL, gas group, temperature class, and dust ratings for anything installed or brought into a hazardous place, including portable equipment and phones.
8. Mark entry points with the "EX" sign where necessary and provide anti-static work clothing where required.
9. Verify explosion safety by a competent person before first use of a new or modified hazardous place (regulation 7(4)).
10. Plan for emergencies, train people, label containers and pipes, and agree coordination with contractors and other employers on site.
11. Record and review: record the significant findings (five or more employees) and review after incidents, process changes, new substances or new equipment.

Whether a particular place needs zoning at all depends on the substances, quantities and conditions; Does it need ATEX zoning? walks through common applications. The decisions belong to the employer's risk assessment, made by competent people.

Enforcement and Penalties

DSEAR is enforced by the Health and Safety Executive (HSE) or local authority inspectors, depending on the type of workplace. At commercial premises holding petroleum licenses, petroleum licensing authorities enforce DSEAR for refueling activities, and at most workplaces fire and rescue authorities enforce the equivalent general fire safety provisions. Enforcement can include:

• Improvement notices: Requiring specific corrective actions within a set timeframe
• Prohibition notices: Stopping work immediately where there is a risk of serious personal injury
• Prosecution: Under the Health and Safety at Work etc. Act 1974, with unlimited fines and, on conviction on indictment, up to two years' imprisonment

Common DSEAR Compliance Mistakes

1. Not recognizing DSEAR applies: Many workplaces use solvents, paints, or cleaning chemicals without realizing DSEAR is relevant
2. Inadequate risk assessment: Generic assessments that don't consider specific substances, quantities, and processes
3. No written record: Employers with five or more employees must record the significant findings, including zones and equipment, wherever explosive atmospheres could form
4. Ignoring dust hazards: Wood dust, flour, sugar, and metal powders can all form explosive atmospheres
5. Outdated zone classifications: Not updating after process changes, new substances, or equipment modifications
6. No explosion-safety verification: New or modified hazardous areas put into use without the competent-person check required by regulation 7(4)
7. Confusion post-Brexit: Assuming DSEAR no longer applies, or that CE-marked ATEX equipment can no longer be used in Great Britain (it can; UKCA and CE are both accepted)

Frequently asked questions

What is DSEAR?

DSEAR is the Dangerous Substances and Explosive Atmospheres Regulations 2002 (SI 2002/2776). It requires employers and the self-employed in Great Britain to assess and control the risks of fire, explosion and similar events from dangerous substances at work, and to classify and control places where explosive atmospheres may occur.

Is DSEAR the same as ATEX?

DSEAR is the Great Britain implementation of the ATEX workplace Directive 1999/92/EC, together with the safety parts of the Chemical Agents Directive 98/24/EC. The zones and equipment categories are the same; equipment itself is covered by the separate Equipment and Protective Systems Regulations 2016 (UKEX).

Who needs a DSEAR risk assessment?

Any employer or self-employed person where a dangerous substance is, or is liable to be, present at the workplace. Employers with five or more employees must also record the significant findings.

Is an explosion protection document required under DSEAR?

Not as a separate document. HSE's L138 explains that the EU requirement is covered in Great Britain by the DSEAR risk assessment and the measures under regulations 5, 6 and 7, so the recorded findings must include the zones, the equipment and the explosion-safety verification.

Can CE-marked ATEX equipment still be used in the UK?

Yes. Great Britain accepts CE-marked equipment indefinitely alongside UKCA marking under the Product Safety and Metrology etc. (Amendment) Regulations 2024, and Northern Ireland follows the EU rules.

Related Pages

• Zone Classification: zones used within DSEAR framework
• UKCA Ex (UKEX) Certification: equipment rules in Great Britain
• Standards: IEC 60079, ATEX, and BS EN standards
• ATEX vs IECEx: certification systems compared
• NEC vs ATEX/IECEx: North American vs international systems
• ATEX Equipment Categories: Category 1, 2, 3 explained
• Fundamentals: explosive atmosphere basics

Sources

1. legislation.gov.uk: The Dangerous Substances and Explosive Atmospheres Regulations 2002 (SI 2002/2776)
2. legislation.gov.uk: DSEAR regulation 5, risk assessment
3. legislation.gov.uk: DSEAR regulation 7, places where explosive atmospheres may occur
4. HSE: The Dangerous Substances and Explosive Atmospheres Regulations 2002
5. HSE: L138 Dangerous substances and explosive atmospheres, Approved Code of Practice and guidance (2nd edition, 2013)
6. HSE: ATEX and explosive atmospheres
7. GOV.UK: Equipment and Protective Systems Regulations 2016, Great Britain guidance (CE and UKCA)
8. legislation.gov.uk: Dangerous Substances and Explosive Atmospheres Regulations (Northern Ireland) 2003