ATEX zones 0, 1, and 2 (for gas) and zones 20, 21, and 22 (for dust) all require a certified ATEX flame detector when a flame detection system is installed in that area. Certification is not optional in any classified zone. The classification determines the category of equipment permitted, and using an uncertified detector in a hazardous area is both a regulatory breach and a serious safety risk. The sections below explain exactly which zones apply, how certification works, and how to confirm compliance before installation.
What makes a flame detector ‘ATEX certified’?
An ATEX certified flame detector is a device that has been independently assessed and confirmed to meet the requirements of the ATEX directive (2014/34/EU), which governs equipment intended for use in explosive atmospheres. Certification confirms that the detector’s design, construction, and materials will not themselves become a source of ignition in the hazardous environment where they are installed.
To carry ATEX certification, a flame detector must be tested and approved by a Notified Body, which is an independent organisation authorised by an EU member state to carry out conformity assessments. The resulting certificate specifies the equipment group, category, and the type of atmosphere (gas, vapour, mist, or dust) for which the device is approved. This information is encoded in the ATEX marking printed on the detector, typically in the format II 2G or II 1G, followed by the specific protection concept used, such as Ex d (flameproof enclosure) or Ex ia (intrinsic safety).
Without this marking and the accompanying documentation, a flame detector cannot legally be installed in any ATEX classified zone, regardless of how technically capable it may otherwise be.
How are ATEX zones 0, 1, and 2 defined for gas and vapour?
ATEX zones for gas and vapour are defined by the frequency and duration with which a flammable atmosphere is present. Zone 0 is the most hazardous, where a flammable gas or vapour mixture is present continuously or for long periods. Zone 1 covers areas where such an atmosphere is likely to occur during normal operation. Zone 2 applies where a flammable atmosphere is not likely during normal operation but may occur under abnormal conditions.
These definitions come from the ATEX workplace directive (1999/92/EC), which requires employers to classify hazardous areas and document the classification in an explosion protection document. In practice, the zone boundaries are determined by factors such as the nature of the substance handled, the quantity released in a potential leak, ventilation conditions, and the operating pressure of the process.
- Zone 0: Continuous presence of an explosive atmosphere (more than 1,000 hours per year as a general guideline)
- Zone 1: Occasional presence during normal operation (between 10 and 1,000 hours per year)
- Zone 2: Rare and brief presence, only under abnormal conditions (fewer than 10 hours per year)
These distinctions directly determine which equipment category is permitted in each zone, which is why accurate zone classification is a prerequisite for selecting the correct flame detector.
Which ATEX zones require a certified flame detector by regulation?
All ATEX classified zones require certified equipment, including flame detectors. There is no zone where an uncertified device is permissible. The difference between zones lies in the required equipment category, not in whether certification is needed at all.
The ATEX equipment directive specifies three equipment categories for gas and vapour environments:
- Category 1G: Required in Zone 0. Highest level of protection, designed to remain safe even when two independent faults occur simultaneously.
- Category 2G: Required in Zone 1. Must remain safe in the event of a single fault.
- Category 3G: Required in Zone 2. Must remain safe during normal operation, with no fault tolerance required beyond standard design.
In all three cases, the equipment must carry a valid ATEX certificate. The stricter the zone, the more rigorous the certification requirements. A flame detector installed in Zone 0 without Category 1G certification would be both non-compliant and potentially dangerous.
What’s the difference between ATEX zones for dust versus gas?
The key difference is that dust zones use a separate numbering system: zones 20, 21, and 22 correspond roughly to zones 0, 1, and 2 for gas, but apply to environments where combustible dust clouds are the hazard rather than flammable gas or vapour. Equipment approved for gas zones is not automatically approved for dust zones, and vice versa.
Combustible dust presents different ignition characteristics compared to gas. Dust clouds can ignite at different energy thresholds, and settled dust layers introduce additional risks that gas atmospheres do not. As a result, ATEX equipment for dust environments carries the suffix D (for dust) rather than G (for gas) in its marking, for example II 2D instead of II 2G.
Flame detectors are most commonly deployed in gas and vapour environments, but in processes such as wood processing, grain handling, or certain chemical manufacturing operations, dust zone classification may be relevant. In those environments, the flame detector must carry the appropriate dust zone certification. Some detectors carry dual certification covering both gas and dust atmospheres, which can simplify equipment selection in mixed-hazard environments.
Can a flame detector approved for Zone 2 be used in Zone 1?
No. A flame detector certified only for Zone 2 (Category 3G) cannot be used in Zone 1. Higher-numbered zones have lower hazard levels, and equipment approved for a less hazardous zone does not meet the stricter protection requirements of a more hazardous one. You must always use equipment certified for the zone in question or a stricter zone.
The logic works in the opposite direction. A Category 1G detector approved for Zone 0 can be used in Zone 1 or Zone 2, because it exceeds the minimum protection level required in those areas. A Category 2G detector approved for Zone 1 can also be used in Zone 2. However, using a lower-category device in a more hazardous zone is a regulatory violation and significantly increases ignition risk.
This is a common source of error during equipment procurement, particularly when a facility expands or reclassifies its zones after initial installation. Always verify the zone classification of the installation location against the category stated on the detector’s ATEX certificate before finalising any equipment selection.
How do you verify a flame detector’s ATEX compliance before installation?
To verify ATEX compliance, check the detector’s marking, its EC-type examination certificate, and the manufacturer’s declaration of conformity. These three documents together confirm that the device has been properly assessed, that the certification covers the intended zone and atmosphere type, and that the manufacturer takes legal responsibility for the product’s conformity.
Follow these steps when verifying compliance:
- Read the ATEX marking on the device. Confirm it includes the equipment group (II for surface industries), category (1, 2, or 3), and atmosphere type (G for gas, D for dust).
- Check the protection concept. The marking will include an Ex code such as Ex d, Ex e, Ex ia, or Ex nA. Verify this is appropriate for the installation conditions.
- Request the EC-type examination certificate. This is issued by the Notified Body and lists the specific conditions and limitations of the approval. Check the certificate number, the issuing body, and the expiry or revision date.
- Review the declaration of conformity. The manufacturer must provide this document, confirming the product meets all applicable ATEX requirements.
- Cross-reference with your zone classification document. Confirm the certified category matches or exceeds the zone where the detector will be installed.
If any of these documents are missing or the marking is unclear, do not proceed with installation until the compliance status is confirmed. Regulators and insurers will expect complete documentation in the event of an audit or incident.
How Anaparts helps with ATEX flame detector selection
Selecting the right ATEX certified flame detector for your specific zone classification, process conditions, and regulatory requirements is not always straightforward. We work with plant safety managers, instrumentation engineers, and compliance officers across the process industry to match the right detection solution to the right application.
Here is what we offer:
- Zone-specific product guidance: We help you identify detectors certified for your exact zone and atmosphere type, whether gas, vapour, or dust.
- Documentation support: We provide complete ATEX certificates, declarations of conformity, and technical datasheets for every product we supply.
- System integration: Beyond individual detectors, we supply complete flame monitoring systems and instrumentation cabinets tailored to your process environment.
- Expert advice: Our team brings deep technical knowledge of ATEX requirements and can advise on category selection, protection concepts, and compliance documentation.
If you are reviewing your hazardous area equipment or planning a new installation, we are ready to help you get it right from the start. Contact us to discuss your requirements.
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