Does it need ATEX zoning? Hazardous area classification by application
A location needs ATEX zoning (hazardous area classification) when a flammable gas, vapor, mist or combustible dust can be present in enough quantity to form an explosive atmosphere with air, in normal operation or in a foreseeable malfunction. Where that is possible and ignition sources are or could be present, the employer must classify the area into zones under Directive 1999/92/EC (DSEAR 2002 in Great Britain), normally using IEC 60079-10-1 for gases and IEC 60079-10-2 for dusts. If the substance cannot burn, or can never reach an explosive concentration, there is nothing to zone.
The three-question test
Every application page in this section works through the same three questions. They mirror the method in IEC 60079-10-1:2020 and IEC 60079-10-2.
- Is there a flammable substance? Flammable gases, liquids that are handled above (or close to) their flash point or released as a mist, and combustible dusts all qualify. Non-flammable gases such as carbon dioxide, nitrogen and argon never create an explosive atmosphere, although they can be lethal for other reasons.
- Can it form an explosive atmosphere? This depends on the sources of release (flanges, seals, vents, charging batteries, open handling of powder), the release rate compared with the lower explosive limit (LEL) or minimum explosible concentration, ventilation, and, for dust, whether layers can build up and be disturbed.
- How often, and for how long? The frequency and duration set the zone type (Zone 0, 1, 2 for gas; Zone 20, 21, 22 for dust). Release rate, ventilation and the density of the gas set how far each zone extends.
The ignition sources on site (electrical equipment, hot surfaces, static, vehicles, hot work) are the reason the classification matters: once zones are drawn, they tell you which equipment and activities are allowed where. See Zone Classification for the zone definitions and Hazardous Area Classification for the full method.
Quick answers by application
Each row links to a page that explains the hazard, what normally decides the zone type and extent, typical equipment requirements, and common mistakes.
| Application | Does it need zoning? | What drives it |
|---|---|---|
| Battery rooms and battery energy storage | Vented lead-acid and NiCd: assessed; usually only a small area near the cells once ventilation is adequate. Lithium-ion: not normally zoned. | Hydrogen released during charging (IEC 62485-2 ventilation). For lithium-ion, thermal runaway gas is handled by NFPA 855 explosion control rather than routine zoning. |
| EV charging | Not in itself. At fuel stations the charger must stay out of the forecourt zones. | Petrol vapor around dispensers, tank fills and vents. The charger, the vehicle and the cable at full reach must be outside the hazardous area. |
| Hydrogen electrolysers | Yes, always assessed. | Hydrogen (gas group IIC, T1). Pressure, release sources and ventilation decide between Zone 1, Zone 2 and Zone 2 NE; vent outlets need their own zones. |
| CO2 (carbon dioxide) | No. CO2 itself never creates a zone. | CO2 is not flammable. Zones come only from other substances in the same area (ethanol, dust, hydrogen, hydrocarbons). The CO2 hazard is asphyxiation and intoxication. |
| Spray booths | Yes, in most cases. | Solvent vapor zones inside and around the booth. |
| Grain silos and flour mills | Yes. | Combustible dust: Zones 20, 21 and 22, including areas where dust layers can build up. |
| Biogas plants | Yes. | Methane (with hydrogen sulfide) around digesters, gas storage and the CHP or gas-handling equipment. |
| Distilleries | Yes. | Ethanol vapor around stills, spirit receivers, casks and filling; grain dust in milling. |
Who decides, and under which rules
Hazardous area classification is the job of whoever controls the workplace. It is not something an equipment supplier or an insurer can do on your behalf, although both can supply input.
| Region | Legal duty | Classification method | Record |
|---|---|---|---|
| EU | Directive 1999/92/EC (ATEX 137 / "ATEX Workplace"), as national law | EN IEC 60079-10-1, EN IEC 60079-10-2, plus industry codes | Explosion protection document |
| Great Britain | DSEAR 2002, regulation 7 and Schedule 2 | BS EN IEC 60079-10-1/-2, Energy Institute codes, HSE guidance | DSEAR risk assessment and area classification drawings |
| US | OSHA 29 CFR 1910.307; NEC (NFPA 70) Articles 500 to 506 as adopted locally | NFPA 497 (gases and vapors), NFPA 499 (dusts), API RP 500/505 for petroleum facilities | Documented classified locations (1910.307(b)) |
| IECEx countries | National workplace law | IEC 60079-10-1:2020, IEC 60079-10-2 | Area classification dossier |
Under DSEAR regulation 7 the employer must classify places into hazardous or non-hazardous, classify hazardous places into zones, mark entry points with the "EX" sign where necessary, and have overall explosion safety verified by a competent person before a workplace containing hazardous places is used for the first time. The equipment itself is then selected to suit the zone: see ATEX equipment categories and Equipment Protection Levels.
IEC 60079-10-2 was revised in June 2026 (edition 3.0, replacing the 2015 edition). Existing classifications made to the 2015 edition do not become invalid overnight, but new studies and reviews should work to the current edition where your national adoption allows it.
From zone to equipment
| Zone | Explosive atmosphere is… | ATEX category | EPL |
|---|---|---|---|
| Zone 0 / Zone 20 | present continuously or for long periods | 1G / 1D | Ga / Da |
| Zone 1 / Zone 21 | likely in normal operation | 2G / 2D (or 1) | Gb / Db (or Ga/Da) |
| Zone 2 / Zone 22 | not likely, and short-lived if it occurs | 3G / 3D (or 1, 2) | Gc / Dc (or higher) |
Gas group and temperature class come from the substance: hydrogen needs IIC (or IIB+H2), most hydrocarbons are IIA, and the temperature class must stay below the auto-ignition temperature. See Gas Groups and Temperature Classes.
What zoning does not cover
Area classification answers one narrow question: where can an explosive atmosphere occur in normal operation or foreseeable malfunction? Several hazards that people search for under "ATEX" sit outside it:
- Catastrophic failures. IEC 60079-10-1 explicitly excludes catastrophic failures and rare malfunctions beyond the concept of normality. Vessel rupture or lithium-ion thermal runaway is handled by other measures (explosion venting, prevention systems, detection, emergency response).
- Toxic and asphyxiant gases. CO2, nitrogen and hydrogen sulfide at toxic concentrations need gas detection, ventilation and confined-space controls, not Ex equipment.
- Oxygen-enriched atmospheres. Zoning assumes a flammable substance mixed with air. Oxygen enrichment increases the flammability of materials and needs its own controls.
- Domestic premises. IEC 60079-10-1 does not apply to domestic premises.
Common mistakes across applications
- Zoning non-flammable gases. CO2 and nitrogen stores are sometimes marked as Ex areas. This adds cost and hides the real hazard, which is oxygen depletion or CO2 intoxication.
- Relying on ventilation without checking its availability. A zone that is small only because a fan is running must consider what happens when the fan stops. IEC 60079-10-1 treats availability of ventilation as part of the assessment.
- Forgetting temporary sources. Tanker deliveries, maintenance openings and filter changes create zones that exist only part of the time but still apply.
- Ignoring dust layers. Settled dust can be raised into a cloud and is a source of release in its own right under IEC 60079-10-2.
- Treating Zone 2 as non-hazardous. Zone 2 still requires equipment suitable for EPL Gc (Category 3G) or better.
- Not reviewing after changes. New equipment in or near a zone (an EV charger on a forecourt, a new vent line) is a change that should trigger a review of the classification.
These pages explain typical practice. The classification for a specific site belongs in that site's explosion protection document or DSEAR assessment, made by a competent person.
Frequently asked questions
How do I know if my site needs ATEX zoning?
Ask three questions: is a flammable gas, vapor, mist or combustible dust present, can it form an explosive atmosphere with air in normal operation or foreseeable malfunction, and how often and for how long. If the answer to the first two is yes, the area must be classified into zones under Directive 1999/92/EC or DSEAR, normally using IEC 60079-10-1 and IEC 60079-10-2.
Who is responsible for hazardous area classification?
The employer or operator who controls the workplace. Under Directive 1999/92/EC and DSEAR regulation 7 they must classify hazardous places into zones and record it in the explosion protection document or DSEAR risk assessment. Equipment suppliers can provide data but do not own the classification.
Do non-flammable gases like CO2 or nitrogen need an ATEX zone?
No. A non-flammable gas cannot form an explosive atmosphere, so it never creates a zone. It can still be deadly through asphyxiation or intoxication, which is controlled with ventilation, gas detection and confined-space procedures.
Is ATEX zoning required in the US?
ATEX is EU law. In the US, hazardous (classified) locations are defined under NEC Articles 500 to 506 using the Class/Division or Zone system, NFPA 497 and 499 give classification guidance, and OSHA 29 CFR 1910.307 requires classified locations to be documented.
Sources
- HSE: ATEX and explosive atmospheres
- legislation.gov.uk: DSEAR 2002, regulation 7 (places where explosive atmospheres may occur)
- IEC: IEC 60079-10-1:2020 Classification of areas - Explosive gas atmospheres
- IEC: IEC 60079-10-2:2026 Classification of areas - Explosive dust atmospheres
- OSHA: 29 CFR 1910.307 Hazardous (classified) locations