ATEX air conditioning for hazardous areas
Updated 23 October 2026 · SEO Dons Editorial
HSE says ATEX is the name commonly given to the legal requirements for controlling explosive atmospheres and for the equipment used in them. For air conditioning, it decides which units may sit inside a zoned area and which must stay outside it.
Why can't a standard air conditioner go in a zoned area?
HSE says using electricity can generate hot surfaces or sparks which can ignite an explosive atmosphere, so equipment in these places must be specially designed so that the risk of ignition is eliminated or reduced. It names three approaches: sealing electrical parts so the atmosphere cannot reach them, reducing the power of electrical equipment, and de-energising it when a fault or an explosive atmosphere is detected. An ordinary split or packaged unit is not built or certified that way.
The rules cover mechanical as well as electrical equipment. HSE adds that equipment is only subject to ATEX if it is intended for use in a potentially explosive atmosphere and has its own potential source of ignition.
Who decides whether an area is hazardous?
The employer does, not the air conditioning supplier. Under DSEAR, employers must identify and classify areas where explosive atmospheres may occur and avoid ignition sources in them. HSE says users have a duty to classify their workplaces and use equipment suitable for the area, and that before a workplace with zoned areas first operates, a competent person or organisation must verify the overall explosion safety measures. The table combines DSEAR Schedule 2 (the zone definitions) with Schedule 3 (the equipment categories allowed).
| Zone (gas or dust) | Meaning in DSEAR | Category allowed |
|---|---|---|
| 0 (gas) or 20 (dust) | Explosive atmosphere present continuously, for long periods or frequently | Category 1 |
| 1 or 21 | Likely to occur in normal operation occasionally | Category 1 or 2 |
| 2 or 22 | Not likely in normal operation and, if it occurs, lasts only a short time | Category 1, 2 or 3 |
What do the markings on ATEX equipment mean?
Under the 2016 equipment regulations, the marking must give the explosion protection marking followed by the equipment group and category, and for group II the letter G (gases, vapours, mists) or D (dust). In plain terms, the Regulations expect category 1 equipment to prevent ignition even in rare incidents, category 2 to cope with frequent disturbances or operating faults, and category 3 to prevent foreseeable ignition sources in normal operation. HSE lists group II category 2 as suitable for zones 1 and 21, and category 3 for zones 2 and 22.
As an example, a manufacturer's ATEX split unit page prints the outdoor unit marking II 3G Ex ec h ic mc IIC T3 Gc. That reads as group II, category 3, gas atmospheres, which suits zone 2. The rest of the string is for the certificate and instructions to explain, so match them to the substances on site rather than relying on a headline.
What are the options for cooling in or near a hazardous area?
| Option | How it works | What to check |
|---|---|---|
| Certified unit in the zone | Equipment marked for the zone category; one maker says systems can mix explosion-safe and ordinary units depending on the zoning where each part sits | Category, gas group, temperature class, ambient range |
| Plant outside the zone | Cooling is delivered by ducts or pipes from a safe area | DSEAR's risk assessment must consider places connected via openings, and ducts and penetrations are openings |
| Pressurised or sealed enclosure | HSE lists sealing equipment so the atmosphere cannot reach it | A pressurised cabin built on site from certified products is an installation, with extra ignition risks assessed under DSEAR |
| Remove the heat or the people | Move heat-producing equipment or staff to a safe-area room | Whether the process allows it |
HSE says equipment in these areas must be regularly inspected and maintained by competent people, and points to BS EN 60079 part 17 for the frequency and scope. The general electrical side of commercial air conditioning is covered in electrical supply for commercial air conditioning; inside a zone the installation must also suit the area, so the electrician needs to be competent in hazardous-area work. For chilled-water loops from a plant sited elsewhere, see process and glycol chillers.
Which sites need it?
HSE lists places such as vehicle paint spraying, workplaces handling fine organic dusts such as grain, flour or wood, paint spray booths, areas near fuel tanks, and sumps. Dangerous substances include petrol, LPG, paints, varnishes, solvents and dusts. The manufacturer page above says its units are used in offices, offshore temporary living quarters, crane cabins and chemical and flammable-substance stores. The industrial air conditioning overview covers cooling jobs that sit outside zoned areas.
What changes between Great Britain and Northern Ireland?
In Great Britain, new equipment must be UKCA or CE marked, with a Declaration of Conformity and instructions in English, according to HSE. The GOV.UK guide says CE marking recognition was extended indefinitely from 1 October 2024, so either mark is accepted on the GB market. Northern Ireland has its own Dangerous Substances and Explosive Atmospheres Regulations of 2003, with the GB code of practice approved for use there by HSENI, and separate equipment regulations. HSE adds that equipment already in use before July 2003 can continue indefinitely if a risk assessment shows it is safe.
Does a flammable refrigerant bring DSEAR into play?
HSE defines dangerous substances as anything used or present at work that could cause harm through fire, explosion or corrosion of metal. A flammable refrigerant falls within that wording, so the assessment should cover leaks even in an ordinary room. The R290 guide covers charge limits.
What should an ATEX cooling brief include?
- The area classification: zones, extents and drawings.
- The substances present, and the category and temperature class needed.
- The cooling load and the ambient temperature range.
- Which parts sit inside the zone and how ducts or pipes cross its boundary.
- The marking, Declaration of Conformity and English instructions for each item.
- The inspection and maintenance regime, and who is competent to carry it out.
- Power and efficiency data: the retained fan ecodesign regulation does not apply to fans designed specifically for potentially explosive atmospheres, so ask for the figures.
Readers specifying cooling for a hazardous process can send an enquiry through the form on this page, or start from the industrial air conditioning overview.
Sources
All pages checked 22 October 2026.
- HSE: General, guidance and enforcement issues; Electricity in potentially explosive atmospheres (updated 3 April 2025); DSEAR (updated 14 October 2024); ATEX equipment and explosive atmospheres (updated 26 January 2026); Definitions; Interpretation, checked 22 October 2026.
- legislation.gov.uk: DSEAR 2002 Schedule 2, Schedule 3 and regulation 5; EPS Regulations 2016, Schedule 1; DSEAR (Northern Ireland) 2003; Regulation (EU) No 327/2011, article 1, checked 22 October 2026.
- GOV.UK (OPSS): EPS Regulations 2016: Great Britain guide (updated 24 March 2025); Equipment for explosive atmospheres regulations, checked 22 October 2026.
- HSENI: L138 approved for use in Northern Ireland (6 January 2014), checked 22 October 2026.
- IKM HVAC (manufacturer, facts about its own units only): ATEX split unit, checked 22 October 2026.
Common questions
Is UKEX the same as ATEX?
ATEX is the name commonly given to the legal requirements, according to HSE. In Great Britain the equipment rules are the 2016 EPS Regulations, with UKCA or CE marking accepted. Some suppliers use UKEX as shorthand, but the GOV.UK guide checked for this page does not, so rely on the marking and certificate.
Does a Zone 2 area need ATEX air conditioning?
Equipment in a zone 2 or 22 area must be category 1, 2 or 3 under DSEAR Schedule 3. An ordinary unit is not marked for that, so it needs to be moved outside the zone or replaced by suitably marked equipment.
Who certifies ATEX equipment?
HSE says certification usually involves a third-party conformity assessment body, but manufacturers can self-certify equipment for less hazardous atmospheres. The employer's separate duty is to classify the area and confirm that overall explosion safety is verified by a competent person.
Can older ATEX-area equipment stay in use?
HSE says equipment already in use before July 2003 can continue to be used indefinitely, provided a risk assessment shows it is safe to do so. New equipment placed on the market must meet the 2016 equipment regulations.
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