Hazardous Area Classification

Defining Where Risk Lives

Hazardous Area Classification (HAC) is the process of mapping out where flammable gases, vapours, mists or combustible dusts could form explosive atmospheres, and identifying what to do about it.

An assessment is required within DSEAR legislation, but more than that, it’s a key step in keeping people safe.

If you’re working with flammables and combustibles, knowing exactly where a spark could set things off is non-negotiable.

We help clients take a balanced, site-specific approach, based on real data and realistic assumptions, not worst-case guesswork or over-zoned drawings copied from decades ago.

What a HAC Study Covers

We carry out HAC studies to identify where explosive atmospheres might occur, and what needs to be done about them. That means taking the information from a DSEAR risk assessment looking at what’s stored or used on site and where flammable releases could happen and turning this into understanding of how far they might spread, and whether the right safeguards are in place. Every zone plan we create is grounded in recognised guidance and shaped by real-world experience.

01 | Site Familiarisation & Scope

We’ll start by reviewing your operations, drawings, and flammables. Then we’ll define the scope: which parts of the site we’re assessing, and under what conditions.

This can be undertaken as part of a new DSEAR risk assessment, or from an existing one if still representative of site conditions.

02 | Source Identification

We identify credible release points – valves, flanges, vents, and other potential failure spots, and assess their release frequency and nature based on how your site actually runs.

03 | Ventilation & Dispersion Assessment

We look at ventilation (forced or natural), containment, and physical layout to understand how the flammable or combustible substance would behave if released.

This helps us define the shape and extent of hazardous zones.

04 | Zoning & Documentation

All findings are documented in a structured, actionable report. We don’t just list problems, we explain the context, clarify responsibilities, and help prioritise the fixes.

We’ll also track actions and support with any follow-up as needed. We include diagrams showing the shape of your zones from multiple perspectives, and can also overlay these onto your site drawings if required.

Why A Good HAC Matters

Clear zoning avoids both danger and overkill
Poor classification can lead to real risk – or massive overspend. We help you get it right, based on what’s actually on site, not just what the textbook says.
Supports compliance with DSEAR, COSHH & COMAH
A documented HAC is required under DSEAR and also forms part of many safety cases under COMAH. Ours are written to support regulatory confidence, not just as a tick a box.
Protects workers, equipment and business continuity
When zones are clearly defined and ignition sources properly controlled, the chance of an explosive atmosphere igniting is dramatically reduced.

Get In Touch

Need a fresh set of zone drawings? Looking to update a HAC study after a site change or expansion? Get in touch with our team to arrange a scoping chat and find the best approach for your facility.

Get In Touch