What is DSEAR?

Get in touch as you may need a DSEAR assessment if you answer “yes” to any of the following questions:

DSEAR stands for the Dangerous Substances and Explosive Atmospheres Regulations 2002. It is a piece of UK legislation that requires employers to identify, assess and control risks where dangerous substances could cause fire, explosion, or corrosion.

DSEAR applies to any site in the UK where these substances could create an explosive atmosphere. Not just heavy industries like refineries are included, but smaller businesses such as woodworking shops, food manufacturers, or warehouses storing aerosols and solvents will all fall under DSEAR.

The DSEAR legislation was introduced in 2002, originally driven by two European Directives: the Chemical Agents Directive (98/24/EC) and the Explosive Atmospheres Directive (ATEX, 99/92/EC). In 2015, its scope was extended to cover gases under pressure and substances corrosive to metals.

Sites that store dangerous substances above certain threshold quantities may also fall under COMAH 2015 (Control of Major Accident Hazards), a separate but complementary regime that places additional safety and emergency planning duties on operators.

Yes. DSEAR is a legal requirement for both employers and the self-employed. Its purpose is to protect workers, the public, and the environment from the risks of fire and explosions caused by dangerous substances in the workplace.

Employers must assess all sites where hazardous environments may exist, including gasworks, furnaces, refineries, foundries, and storage tanks. Even industries that don’t typically handle flammable substances, such as woodworking shops or food manufacturers, may create combustible dusts and powders as by-products.

A useful starting point, therefore, is the dust combustibility test (Group A/B). This qualitative test determines whether dust or powder can form a flammable atmosphere or support flame propagation when dispersed in air. This test will classify your materials as either:

• Group A – Combustible: Flammable or explosive
• Group B – Non-Combustible: Non-flammable or non-explosive

Dangerous substances are materials used or stored in the workplace that, if not properly controlled, can create fire and explosion hazards in an explosive atmosphere.

Compliance with DSEAR requires that these risks are either eliminated or effectively managed to protect employees and the public from fire and explosion.

Examples of dangerous substances commonly found in workplaces include:

• Solvents and paints
• Flammable gases and vapours
• Combustible dusts from machining, sanding, or food processing
• Pressurised gases
• Flammable liquids

Essentially, any substance with the potential to ignite or explode under certain conditions falls under DSEAR’s scope. It helps to understand the difference between flammability and combustibility, since the two behave differently and are tested in different ways.

Under DSEAR, a workplace is defined as “any premises or parts of premises used for work.” This broad definition can include:

• Industrial and commercial properties
• Land and offshore operations (with some exceptions)
• Construction sites and vehicles
• Common areas in shared buildings
• Private and public roads
• Domestic properties, if used for work purposes

However, certain DSEAR requirements may not apply to specific industries or locations, for example some offshore oil production sites.

Again, if you’re unsure whether your workplace falls under DSEAR regulations, it’s always best to consult a competent person to ensure full legal compliance.

DSEAR helps workplaces identify where explosive atmospheres may or may not occur. By defining potentially hazardous zones, businesses can implement safeguards to protect people, property, and the environment.

A Hazardous Area Classification (HAC) identifies areas where control measures are necessary.

Accurate HAC documentation is essential across many industries, as it determines the appropriate electrical and non-electrical equipment allowed within each classified zone. This ensures that devices installed in these areas do not act as sources of ignition, reducing the risk of fire or explosion.

HAC also guides safe operational practices, including:

• Proper placement and storage of flammable materials.
• Selection of ventilation and extraction systems to prevent the accumulation of explosive atmospheres.
• Employee training and access restrictions to hazardous zones.
• Routine inspection and maintenance of equipment in hazardous areas.

By clearly defining and controlling these zones, employers can demonstrate regulatory compliance, protect staff, and minimize the potential for costly accidents or downtime.

DSEAR regulations are designed to protect people, property, and the environment from the risks of fire, explosion, and chemical reactions associated with dangerous substances. They apply whenever there is a potential for a hazardous atmosphere in the workplace.

For a fire or explosion risk to exist under DSEAR, three elements must come together:

• A dangerous substance (e.g. flammable liquid, vapour, or dust)
• A flammable or explosive atmosphere
• An ignition source (e.g. sparks, hot work, static discharge). Read our DSEAR for pumping station case study that discusses ignition sources and DSEAR.

Specifically, DSEAR applies if:

• Work is being conducted by an employer or a self-employed person: Any organisation or individual carrying out tasks where dangerous substances are present must comply with DSEAR. Compliance is not limited to large industrial operations. It can also apply to small businesses, workshops, and even construction sites.
• A dangerous substance is present or liable to be present: This includes substances that are flammable, explosive, or corrosive to metals. Dangerous substances can exist in many forms, such as gases, vapours, liquids, mists, or dust. For example:
  • Wood dust in a carpentry workshop
  • Flour or sugar dust in food processing
  • Solvents in paint or cleaning operations
  • Pressurised gases in laboratories or industrial plants
• Flammable substances are being stored, handled, or transported: DSEAR applies not only to substances on site but also during transport within the premises, such as moving LPG cylinders, chemical containers, or other volatile material.

Even if the amount of a dangerous substance seems small, the potential for a flammable atmosphere can make DSEAR relevant.

There is no fixed legal interval for a DSEAR assessment. DSEAR requires you to keep it valid, which means reviewing it whenever something significant changes and whenever you have reason to think it no longer reflects the workplace.

A significant change might be a new substance, a modified process, or altered plant and equipment. Many operators also review every two to three years as good practice. The change on the floor matters more than the date on the calendar, though. A repositioned line, a new dust collector, or a change in throughput can all move a hazardous zone without anyone reopening the file.

A DSEAR assessment must be carried out by a competent person. That means someone with the training, knowledge, and experience to identify the dangerous substances present, judge the risks, and specify controls that hold up.

DSEAR does not issue a certificate for competence, so a job title alone does not make someone competent. For a straightforward site, an in-house team may be. Where you have hazardous area classification, explosive atmospheres, or complex dust risks, most operators bring in a specialist to complete or verify the work.

DSEAR places clear responsibilities on employers to manage the risks from dangerous substances in the workplace.

Employers must:

• Identify dangerous substances: Find out which dangerous substances are present at your workplace and document the risks they pose. This includes flammable gases, vapours, liquids, dusts, and mists.
• Control the risks: Either remove the risks entirely or put measures in place to manage them safely if elimination isn’t possible.
• Reduce the effects of incidents: Plan for potential fires, explosions, or chemical incidents and implement controls to minimise harm.
• Prepare procedures for emergencies: Have plans in place to deal with accidents, incidents, or emergencies involving dangerous substances.
• Train employees: Ensure staff understand the risks and are trained to handle dangerous substances safely.
• Define hazardous areas: Identify parts of the workplace where explosive atmospheres may occur, classify these zones, and make sure equipment used there is safe and ignition sources are controlled.

By following the above, you can ensure that your workplace meets DSEAR requirements and keeps everyone safe.

Regulation 5 of DSEAR focuses on the importance of conducting thorough risk assessments whenever dangerous or potentially dangerous substances are present in the workplace.

According to Regulation 5, a DSEAR risk assessment should consider:

• Hazardous properties of substances: Understand the risks posed by any dangerous or potentially dangerous substance present.
• Supplier safety information: Include details provided by suppliers, such as information on safety data sheets.
• High-risk activities: Take into account activities, such as maintenance, that may increase the level of risk.
• Existing and planned controls: Evaluate the effectiveness of measures already in place or planned under DSEAR.
• Potential for explosive atmospheres: Assess how likely an explosive atmosphere is to occur and how long it could persist.
• Ignition sources: Identify potential ignition sources, including electrostatic discharges, and consider whether they could become active.
• Scale of effects: Predict the possible impact of a fire or explosion.
• Connected areas: Recognize any spaces connected to areas where explosive atmospheres may occur, as these could also be at risk.

Regulation 5 requires employers to assess risks whenever dangerous substances are present. A thorough assessment ensures proper safety measures are in place to protect people in the place of work. The right process hazard analysis tools, such as HAZID and HAZOP, help structure that assessment so nothing is missed.

Regulation 6 focuses on removing or reducing risks from dangerous substances wherever reasonably practicable. This can include replacing hazardous substances or processes and applying control measures such as:

• Minimising the quantity of dangerous substances
• Preventing or controlling their release
• Avoiding the formation of explosive atmospheres
• Using proper ventilation and safe collection or containment
• Eliminating ignition sources and segregating incompatible substances

Employers should also mitigate the effects of potential incidents by reducing employee exposure, preventing fire or explosion propagation, using explosion relief or suppression systems, ensuring plant resilience, providing PPE, and maintaining consistent risk controls.

Regulation 7 focuses on identifying and managing areas where explosive atmospheres could occur.

Employers must classify all potentially hazardous zones in the workplace and clearly mark them at entry points so that everyone is aware of the risk. These zones should only use equipment and systems that are appropriately protected to prevent ignition.

Additionally, employers are required to provide employees with suitable clothing and personal protective equipment that won’t generate electrostatic discharges, helping to reduce the risk of sparks that could trigger a fire or explosion.

You can read more about DSEAR and Regulation 7 in our dedicated blog.

Regulation 8 ensures that workplaces are prepared to handle accidents, incidents, or emergencies involving dangerous substances.

Employers must have clear procedures in place, including:

• Readily accessible safety information, warning systems, and operational escape routes to guide employees during emergencies.
• Appropriate first aid facilities that are easily available and maintained.
• Regular safety drills to ensure employees know how to respond effectively in emergencies.
• Detailed documentation for emergency services, including potential hazards and hazard identification, so responders can act safely and efficiently.
• Active and well-understood warning and communication systems to keep employees informed of risks.
• Adequate and maintained escape facilities to allow prompt and safe evacuation from dangerous areas.

Employers must also take steps to fully mitigate the consequences of any incident. After an event or near-miss, processes should be restored to normal as much as possible, and affected employees must be debriefed.

Only authorized personnel should enter the affected area, equipped with appropriate PPE and specialized safety equipment to handle repairs or recovery safely.

Regulation 9 ensures that all employees are fully informed and trained to work safely around dangerous substances. Employers must:

• Provide clear, up-to-date information, instruction, and training so employees understand the precautions and actions required to safeguard themselves and others.
• Make information about hazardous substances, such as names, risks, safety data sheets, and relevant legislation, freely available at the workplace.
• Include significant findings from any risk assessments, ensuring employees know the potential hazards and how they are controlled.

This regulation ensures that staff are not only aware of the dangers present but are also empowered with the knowledge and skills to work safely and respond appropriately in any situation.

Regulation 10 ensures that all containers and pipes holding dangerous substances are clearly marked and easily identifiable. Employers must:

• Label containers and pipes according to relevant requirements to clearly show their hazardous contents.
• Ensure employees and others in the workplace are aware of the presence of dangerous substances, enabling appropriate precautions to be taken.
• Use clear identification to prevent confusion or accidental mixing of dangerous substances, reducing the risk of incidents.

Proper labelling and awareness are crucial for maintaining a safe working environment and supporting the overall goals of DSEAR compliance.

DSEAR, along with other regulations covering potentially explosive atmospheres, is enforced by the Health and Safety Executive (HSE) or local authorities, depending on your workplace. 

While this blog highlights key requirements of DSEAR, full compliance can only be guaranteed when a competent person conducts a thorough assessment.

Sigma-HSE are recognised experts in DSEAR and have carried out risk assessments across a wide range of processing industries for many years. 

Our consultancy team works closely with businesses to provide practical, cost- and time-effective safety solutions through comprehensive DSEAR risk assessments.

If you are unsure about the fire or explosion risks associated with substances in your facility, Sigma-HSE’s accredited testing laboratory can perform all necessary testing to the relevant standards, offering a fast turnaround.

For organisations in the EU, or those looking to meet ATEX Directive requirements, further guidance is available on our dedicated ATEX Compliance page. 

Additional DSEAR resources can also be explored here.

No, though they often apply to the same substance. COSHH covers the health effects of hazardous substances, such as toxicity and long-term exposure. DSEAR covers the safety effects, meaning fire, explosion, and similar energetic events. A solvent can fall under both at once. COSHH asks whether it will harm someone’s health. DSEAR asks whether it will ignite.

Yes. Diesel is a dangerous substance under DSEAR because it can burn. Its high flash point means it behaves differently from petrol and often sits at a lower risk, but that does not put it outside the regulations. You still need to assess how it is stored, handled, and used, and control the fire risk. We cover this further in our note on diesel and process safety.

Learn more about DSEAR in our FREE on-demand webinar.