ATEX Hazardous Area Lighting: A Specifier's Guide

What is ATEX?

ATEX derives from the French 'Atmosphères Explosibles' and refers to two EU Directives governing explosive atmospheres:

• ATEX Equipment Directive (2014/34/EU) — covers equipment and protective systems intended for use in explosive atmospheres. Post-Brexit, the UK has retained this as the UKEX regime under the Supply of Machinery (Safety) Regulations.

• ATEX Workplace Directive (1999/92/EC) — covers minimum requirements for improving safety and health protection of workers potentially at risk from explosive atmospheres. Implemented in the UK as DSEAR (Dangerous Substances and Explosive Atmospheres Regulations 2002).

Any luminaire installed in a classified hazardous area must carry ATEX (or UKCA) certification appropriate to the zone, gas group and temperature class of the specific location.

Hazardous Area Zone Classification

Hazardous areas are classified into zones based on the frequency and duration of the explosive atmosphere:

Gas/Vapour Zones: • Zone 0 — explosive atmosphere present continuously or for long periods (e.g., inside a fuel tank). Equipment Category 1 required. • Zone 1 — explosive atmosphere likely to occur in normal operation (e.g., near a pump seal or filling point). Equipment Category 2 required. • Zone 2 — explosive atmosphere not likely in normal operation and, if it occurs, only for a short period (e.g., near a flange joint or valve). Equipment Category 3 required.

Dust Zones: • Zone 20 — combustible dust cloud present continuously (e.g., inside a hopper). Equipment Category 1 required. • Zone 21 — combustible dust cloud likely in normal operation (e.g., near powder handling equipment). Equipment Category 2 required. • Zone 22 — combustible dust cloud not likely and only for a short period (e.g., near bagging operations). Equipment Category 3 required.

The zone classification is determined by the site operator and documented in a hazardous area classification drawing, typically produced by a specialist consultant.

Equipment Categories and Protection Concepts

ATEX-certified luminaires use various protection concepts to prevent ignition:

• Ex d (Flameproof enclosure) — the enclosure can withstand an internal explosion and prevent it propagating to the surrounding atmosphere. Common for Zone 1 luminaires. Heavy, robust construction with machined flameproof joints.

• Ex e (Increased safety) — enhanced measures prevent sparks, arcs or hot surfaces. No sparking components are used. Common for Zone 1 and Zone 2 luminaires. Lighter than Ex d.

• Ex n (Non-sparking) — simplified protection for Zone 2 only. The luminaire is designed so that it is not capable of igniting a surrounding explosive atmosphere in normal operation.

• Ex t (Dust protection) — enclosure prevents ingress of dust to a level that could cause ignition. Used for Zone 21 and Zone 22 applications.

LED luminaires are particularly well-suited to hazardous areas because they operate at low temperatures, contain no glass envelopes (unlike fluorescent or discharge lamps) and have no hot filaments.

Temperature Classes

Every flammable gas or vapour has an auto-ignition temperature — the temperature at which it will ignite without a spark. ATEX luminaires are assigned a temperature class (T-class) indicating the maximum surface temperature under fault conditions:

• T1 — maximum 450°C • T2 — maximum 300°C • T3 — maximum 200°C • T4 — maximum 135°C • T5 — maximum 100°C • T6 — maximum 85°C

The luminaire's T-class must be equal to or lower than the auto-ignition temperature of the gas present. For example, hydrogen (auto-ignition 560°C) requires T1 minimum, while carbon disulphide (auto-ignition 90°C) requires T6.

LED luminaires typically achieve T4 or better (surface temperatures well below 135°C), making them suitable for the vast majority of hazardous area applications.

Specifying ATEX LED Luminaires

A practical specification checklist:

1. Obtain the hazardous area classification drawing — confirm the zone, gas group (IIA, IIB or IIC) and required T-class for each luminaire location

2. Specify luminaires with the correct ATEX/UKCA marking — e.g., Ex II 2 G Ex e IIC T4 Gb for a Zone 1 gas environment

3. Verify the certificate — ATEX certificates are issued by Notified Bodies (e.g., Baseefa, SGS, Dekra). The certificate number must appear on the luminaire nameplate

4. Consider IP rating — hazardous area luminaires typically require IP66 minimum due to the harsh environments (chemical plants, refineries, offshore platforms)

5. Specify appropriate cable glands — Ex-rated cable glands must match the luminaire's protection concept. Standard cable glands invalidate the ATEX certification

6. Installation must be carried out by CompEx-certified electricians — this is a legal requirement under DSEAR

7. Ensure maintenance procedures maintain the integrity of the certification — replacing components with non-certified parts invalidates the ATEX rating

EOS ATEX-certified luminaires are available for Zone 1, Zone 2, Zone 21 and Zone 22 applications, with full IECEx and UKCA certification.