ATEX equipment categories define the level of protection and the zones where equipment may be installed. Category 1 (marked II 1G or II 1D) is approved for Zone 0 or Zone 20 — areas with continuous explosive atmospheres. Category 2 (II 2G or II 2D) covers Zone 1/21. Category 3 (II 3G or II 3D) covers Zone 2/22. Most explosion-proof cameras are Category 2 and are suitable for both Zone 1 and Zone 2 installations.
The ATEX Equipment Directive (2014/34/EU) requires all equipment placed on the European market for use in potentially explosive atmospheres to carry a category marking. This category determines which zones the equipment may legally be installed in. Selecting equipment with the wrong category — for example, installing a Category 3 camera in a Zone 1 area — is a compliance violation under the ATEX Workplace Directive (1999/92/EC) and creates liability in the event of an incident. This guide explains each category in practical terms, how to read the marking, and what it means for explosion-proof camera selection.
ATEX Category 1: Continuous Hazardous Atmospheres (Zone 0 / Zone 20)
Category 1 equipment is designed and built to provide a very high level of protection. It must remain safe even when two independent faults occur simultaneously. For gas and vapor environments, Category 1G equipment may be installed in Zone 0 (explosive atmosphere present continuously or for long periods — more than 1,000 hours per year), Zone 1, and Zone 2. For dust environments, Category 1D may be installed in Zone 20, 21, and 22.
In practice, Zone 0 locations are rare and highly restricted: the interior of tanks containing flammable liquids, the space directly above the surface of an open sump, or enclosed spaces around fuel vapor recovery systems. Fixed cameras are almost never installed inside Zone 0 — the combination of electrical equipment and continuous explosive atmosphere is avoided by design. Category 1 cameras do exist (primarily for special applications such as endoscopes inserted into vessels) but are not commonly used for perimeter or process area surveillance.
ATEX Category 2: Zone 1 and Zone 2 Applications
Category 2 is the most common category for industrial explosion-proof cameras. Category 2G equipment (for gas) is approved for Zone 1 and Zone 2. Category 2D (for dust) is approved for Zone 21 and Zone 22. The equipment must remain safe with one expected fault — meaning a single failure in the protection system must not create an ignition source.
Zone 1 environments include: compressor rooms where natural gas is handled, open-air areas around flanged connections on gas pipelines, chemical plant process areas where vapors are routinely present during operations, and pump areas handling volatile liquids. These are the most common camera installation zones in oil and gas and chemical facilities. Most Veilux SVEX-series cameras carry Category 2G certification (marked II 2G), making them suitable for both Zone 1 and Zone 2 surveillance applications. For details on how ATEX zones are defined and measured, see our hazardous location classification guide.
ATEX Category 3: Zone 2 and Zone 22 (Abnormal Release Only)
Category 3 equipment provides the minimum level of protection required by the ATEX directive. Category 3G is approved only for Zone 2 — areas where a flammable atmosphere is not likely to occur in normal operation and, if it does occur, will exist only for a short time. Category 3 equipment must remain safe during normal operation but is not required to maintain protection under fault conditions.
Zone 2 locations are more common than Zone 1 in many facilities: the area within 1-3 meters of flanged connections in natural gas pipe racks, the exterior of buildings housing Zone 1 processes, loading and unloading areas for volatile chemicals. Category 3G cameras are less expensive than Category 2G but cannot be moved up to Zone 1 if the area classification is revised. Specifying Category 2G throughout a facility simplifies procurement and provides a compliance margin if Zone extents are later extended during a re-classification study.
ATEX Category Marking: How to Read the Equipment Label
| Marking Code | Category | Approved Zones (Gas) | Protection Level |
|---|---|---|---|
| II 1G | Category 1 (Gas) | Zone 0, 1, 2 | 2 independent faults |
| II 2G | Category 2 (Gas) | Zone 1, 2 | 1 expected fault |
| II 3G | Category 3 (Gas) | Zone 2 only | Normal operation only |
| II 1D | Category 1 (Dust) | Zone 20, 21, 22 | 2 independent faults |
| II 2D | Category 2 (Dust) | Zone 21, 22 | 1 expected fault |
| II 3D | Category 3 (Dust) | Zone 22 only | Normal operation only |
A full ATEX marking on a camera might read: Ex II 2G Ex d IIB T4 Gb. Breaking this down: Ex = certified to IEC 60079, II = surface industry (not mining), 2G = Category 2, gas, Ex d = flameproof enclosure, IIB = gas group (covers ethylene, propane, and most common industrial gases), T4 = maximum surface temperature 135°C, Gb = Equipment Protection Level b (reliable, one fault). Reading each field correctly is essential when specifying cameras for a specific zone and gas group.
Group I vs. Group II: Mining vs. Surface Industries
The ATEX marking “II” in the category code refers to Group II — surface industry applications. Group I equipment is specifically for mining environments (underground coal mines and similar), where methane (firedamp) is the primary hazard. Group I equipment carries different marking (just “I” without a category number in the older system). Explosion-proof cameras for oil and gas, chemical, and offshore applications are all Group II equipment. Mining cameras operating in underground environments will typically be Group I if the hazard is methane, or Group II if the mine uses the surface-equivalent zone classification.
Understanding category, group, and zone together allows you to write a complete specification. When combining this with the housing selection guide, you can specify a camera that meets both the hazardous area protection requirements and the physical environment demands (temperature, corrosion, IP rating).
Frequently Asked Questions
Can Category 2 equipment be used in Zone 2?
Yes. Category 2 approved for Zone 1 may also be installed in Zone 2. Higher-category equipment can always be installed in a lower-risk zone. Zone 2 requires a minimum of Category 3, but Category 2 is frequently specified throughout a facility to avoid maintaining two separate equipment classes.
What does II 2G mean on an ATEX label?
II 2G indicates: Group II (surface industry), Category 2 (Zone 1 and Zone 2 approved, safe with one expected fault), G (gas/vapor hazard). This is the most common ATEX marking on industrial explosion-proof cameras.
Is ATEX Category 2 the same as Class I Division 1?
They are broadly similar. Class I Division 1 encompasses Zone 0 + Zone 1 conditions; ATEX Category 2G covers Zone 1. For most industrial applications, Category 2G equipment is accepted as equivalent to Division 1 on dual-certified products, but verify the specific certificate.
Does ATEX category cover both gas and dust?
Not with one marking. Gas uses G suffix (II 2G); dust uses D suffix (II 2D). Some equipment is dual-certified with both markings (II 2GD), allowing installation in combined gas-and-dust areas.
What is Equipment Protection Level (EPL)?
EPL (Ga/Gb/Gc for gas, Da/Db/Dc for dust) is a newer marking that supplements or replaces the category number. EPL Gb = Category 2G (Zone 1 safe, one fault tolerated). Both systems may appear on the same label.
Veilux SVEX-series cameras hold ATEX Category 2G (II 2G) and IECEx Zone 1 certifications, suitable for the most common industrial hazardous area zones. Request a quote and our team will confirm the correct category and gas group for your application.
Key Industry Standards and References
ATEX equipment categories are defined in IEC 60079-0 and the ATEX Directive 2014/34/EU. IECEx certification details are available at IECEx.com.
Related Resources
- ATEX Zone 0, Zone 1, Zone 2 Camera Selection Guide
- IECEx vs ATEX Certification Differences
- NEC Article 505 Zone System vs Article 500 Division System
- Class I vs Class II vs Class III Hazardous Locations
- Explosion-Proof Camera Certification Audit Guide
- Explosion-Proof Camera Selection Guide
About the Author
Daniel Fernandez
Daniel Fernandez is a hazardous area security systems specialist with over a decade of experience specifying ATEX, IECEx, UL Class I Division 1, and cUL certified surveillance equipment for oil and gas, chemical, mining, pharmaceutical, and offshore environments. He holds expertise in NEC and IEC area classification standards and has consulted on explosion-proof camera system designs across North America, Europe, and the Middle East.