Hazardous Area Classification, DSEAR Zones and Regulation 7 Non-Conformance

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Many businesses assume their assessment is valid — until regulators point out gaps. One of the most common problems we see is non-conformance with Regulation 7, which requires a Hazardous Area Classification (HAC).

At Sigma-HSE, we’ve carried out hundreds of DSEAR assessments, reviews, and process safety projects across multiple industries. Again and again, we find external reports missing this critical element — leaving businesses exposed to both safety risks and legal challenges.

In this short DSEAR article, we’ll explain:

• What DSEAR is and why it matters.
• What a Hazardous Area Classification (HAC) involves.
• What Regulation 7 specifically requires.
• How to check if your DSEAR assessment is valid.

DSEAR stands for the Dangerous Substances and Explosive Atmospheres Regulations 2002. It’s the UK law that requires employers to assess, eliminate, or control the risks of fire, explosion, or corrosion caused by dangerous substances.

In practical terms, a DSEAR assessment should look at:

• Where dangerous substances are present – such as flammable gases, vapours, liquids, dusts, or even substances corrosive to metals.
• Where explosive atmospheres could form – for example, in storage tanks, silos, spray booths, or poorly ventilated areas.
• What ignition sources exist – including electrical equipment, hot surfaces, static discharge, and even some types of work clothing.

It’s important to remember that DSEAR applies across many industries, not just chemical plants. Food processing, manufacturing, waste handling, pharmaceutical, and even workshops using solvents or flammable dusts can all fall under its scope.

A Hazardous Area Classification (HAC) is the process of mapping out areas in your workplace where a flammable or explosive atmosphere could form. It looks at the likelihood and extent of that atmosphere being present, based on the combination of fuel and air (an oxidant).

Once those areas are identified, any equipment within them must be specially designed and certified so it cannot act as an ignition source. This is where ATEX-rated equipment comes in.

A thorough HAC will typically include:

• Identification of potential flammable substances (gases, vapours, liquids, dusts).
• Assessment of ventilation – natural airflow, extraction systems, or mechanical circulation.
• Consideration of operational factors – such as temperature, pressure, maintenance practices, and potential for leaks or spills.
• Classification of zones (Zone 0/1/2 for gases and vapours, Zone 20/21/22 for dusts), each with different requirements for equipment and safety controls.

A HAC should show you where explosive atmospheres could exist and ensures you use the right controls and equipment in those zones.

Under DSEAR, Regulation 7 makes a Hazardous Area Classification (HAC) a legal requirement. It requires every employer to assess and classify any workplace areas where an explosive atmosphere could form.

In simple terms, Regulation 7 means you must:

1. Classify areas of your site as either hazardous or non-hazardous.

(1) Every employer shall classify places at the workplace where an explosive atmosphere may occur into hazardous or non-hazardous places in accordance with paragraph 1 of Schedule 2 and shall classify those places so classified as hazardous into zones in accordance with paragraph 2 of that Schedule; and that Schedule shall have effect subject to the notes at the end of that Schedule.

2. Divide hazardous areas into zones (Zone 0/1/2 for gases, Zone 20/21/22 for dusts) based on the likelihood of explosive atmospheres.

(2) The employer shall ensure that the requirements specified in Schedule 3 are applied to equipment and protective systems in the places classified as hazardous pursuant to paragraph (1).

3. Apply strict equipment rules – all equipment in these zones must meet ATEX standards (Schedule 3).

(3) Where necessary, places classified as hazardous pursuant to paragraph (1) shall be marked by the employer with signs at their points of entry in accordance with Schedule 4.

4. Mark hazardous zones with signs where necessary (Schedule 4).

(4) Before a workplace containing places classified as hazardous pursuant to paragraph (1) is used for the first time, the employer shall ensure that its overall explosion safety is verified by a person who is competent in the field of explosion protection because of his experience or any professional training or both.

5. Verify explosion safety before the workplace is used, with checks carried out by a competent person.

(5) The employer shall ensure that appropriate work clothing which doesn’t give rise to electrostatic discharges is provided for use in places classified as hazardous pursuant to paragraph (1).

Regulation 7 specifically pertains to the assessment and classification of zones where potentially explosive atmospheres may occur. This regulation outlines the systematic approach that businesses must adopt, to identify areas where the presence of dangerous substances could lead to the formation of explosive atmospheres.

The Hazardous Area Classification (HAC) section of your DSEAR report must be detailed and systematic, not a generic add-on. Its purpose is to clearly identify areas where explosive atmospheres could develop and explain how risks will be controlled.

A well-prepared HAC report should include:

• A site overview and process description – outlining where dangerous substances are present.
• Identification of flammable or explosive materials (gases, vapours, dusts, liquids).
• Assessment of zones (0/1/2 or 20/21/22) with clear justifications.
• Recommended control measures and mitigation strategies, such as ventilation, ATEX-rated equipment, or procedural safeguards.
• A clear statement of the ‘Basis of Safety’ – how people are protected from fires and explosions, including measures such as explosion relief, containment, or suppression.

If your DSEAR report is missing any of the above elements, or if it pushes them into “future recommendations” instead of including them upfront, then it’s not compliant. 

In that case, you should send the assessment back to the provider and withhold payment until it has been completed properly.

DSEAR is central to protecting people, processes, and facilities from the risks posed by dangerous substances and explosive atmospheres. 

Yet, despite being a legal requirement under Regulation 7, we continue to see DSEAR reports that omit a Hazardous Area Classification (HAC) altogether or reduce it to a vague recommendation. This is not acceptable.

If your assessment doesn’t include a clear HAC section—with zone classifications, identified substances, and a defined Basis of Safety—then it’s incomplete, non-compliant, and potentially unsafe. 

In that situation, you should send it back to your provider and insist it’s finalised correctly before signing off or paying.

At Sigma-HSE, we have reviewed hundreds of such assessments across many industries and know the difference between a tick-box report and a robust, regulator-ready DSEAR assessment. 

If you’re unsure whether your current report meets the requirements of Regulation 7, we strongly recommend getting it reviewed—because the cost of getting it wrong is far greater than the cost of putting it right.

Learn more about Hazardous Area Classification studies in our FREE on-demand webinar.