Zone 0 to Zone 22 is the hazardous-area classification system used under ATEX and IEC standards to grade explosion risk by how often flammable gas, vapor or combustible dust is present: Zones 0/20 (continuous), 1/21 (likely during normal operation) and 2/22 (unlikely, brief only). The zone assigned to an area determines which certified equipment — intrinsically safe, flameproof or dust-tight — is legally required there.
Working facilities that deal with flammable gases and vapors or combustible dusts need to implement specific safety measures against explosions. The fundamental safety precaution involves dividing hazardous spaces into defined risk areas depending on how likely and long explosive vapors can persist.
This article explains the classification system of Z0, Z1, Z2, Z20, Z21, Z22 in basic terms for understanding their role in workplace safety systems.
What Are Zone Classifications?
Hazardous areas are classified by how often an explosive atmosphere is present: Zones 0, 1 and 2 for gases and vapours, and Zones 20, 21 and 22 for combustible dust. Zone 0 and Zone 20 mean an explosive atmosphere is present continuously or for long periods, Zone 1 and Zone 21 mean it is likely during normal operation, and Zone 2 and Zone 22 mean it is unlikely and would be short-lived. The zone decides the equipment protection level you must use, so classifying it wrongly makes every equipment decision downstream wrong too.
The purpose of zone classifications is to determine areas containing flammable gases or vapors along with combustible dust, which leads to explosion hazards. Zone classifications establish the necessary guidelines for industries to decide which equipment and safety measures, and protective systems they require for their operations.
Gas Zones and Dust Zones
- The Gas Zones feature three areas classified as Zone 0, Zone 1, and Zone 2 that correspond to locations with possible flammable gases or vapors.
- These areas refer to Dust Zones Zone 20, Zone 21, along with Zone 2,2, after regulations and their standards identify risk combinations of explosions and fires stemming from combustible dust.
What Are Gas Zones 0, 1 and 2?
Zone 0 has an explosive gas atmosphere continuously or for long periods, Zone 1 has one likely during normal operation, and Zone 2 only rarely and briefly.
Zone 0 (High-Risk Zone)
- A space becomes a Zone 0 area if explosive gas or vapor exists either permanently or persistently.
- An example of Zone 0 occurs inside fuel tanks as well as pipelines and containers that store flammable gases.
- Zones of this type need equipment designed to prevent ignition that meets either intrinsically safe or explosion-proof safety standards.
Zone 1 (Medium-Risk Zone)
- The classification refers to a space where explosive gas or vapor exists occasionally during typical operational activities.
- The areas surrounding fuel pumps, as well as chemical processing units and storage spaces with gas leakages, fall into this category.
- The equipment should undergo certification for hazardous environments with built-in features to stop ignition sources.
Zone 2 (Low-Risk Zone)
- This area contains explosive gas or vapor, which is unlikely to happen naturally, but if it occurs, the presence is brief.
- Examples of these areas include spaces around gas pipes and around both ventilation areas and refueling stations.
- The equipment operating in this zone requires protective measures that do not need full explosion-proof characteristics.
What Are Dust Zones 20, 21 and 22?
Zones 20, 21 and 22 mirror the gas zones for combustible dust: present continuously, likely in normal operation, or unlikely and short-lived respectively.
Zone 20 (High-Risk Zone)
- The definition of this area describes the continuous presence of explosive dust clouds combined with the extended duration of exposure.
- Areas containing silos together with dust collection systems and processing facilities containing abundant fine dusts fall under this category.
- The presence of explosive dust clouds requires equipment to be dust-tight and explosion-proof to prevent ignition.
Zone 21 (Medium-Risk Zone)
- The definition of this area states that it contains explosive dust clouds, but only during normal operational periods.
- The risk area extends from milling and grinding machines, together with locations where powder-handling operations take place.
- Equipment should have sealed enclosures to stop dust accumulation in these areas.
Zone 22 (Low-Risk Zone)
- Zones in this category should not develop explosive dust clouds under normal operations or witness rapid dispersion of such dust formations when they occur.
- Examples: Areas near conveyor belts, storage areas, or ventilation ducts.
- The protection measures to safeguard equipment remain essential in Zone 22 since the risk level is lower than in Zones 20 and 21.
Why Are These Classifications Important?
- The prevention of explosions and fires becomes essential for maintaining worker safety because of proper zone classification applications.
- Select equipment that meets both safety regulations along proper requirements.
- Industries must follow international safety standards ATEX during operations.
- Operational risks, together with downtime reduction, become possible through strategic protective implementations.
How Should Hazardous Zones Be Managed?
- Danger assessment procedures should be performed for hazardous area identification and appropriate classification.
- The correct type of explosion-proof equipment must be selected by reference to zone classification standards.
- The workplace needs sufficient ventilation to minimize the potential buildup of flammable dust and gases.
- A regular maintenance schedule helps workers check for leaks while they identify both dust accumulation and damaged seals and repair them when necessary.
- The organization trains staff members to conduct proper procedures when dealing with hazardous zones..
Which Industries Use Zone Classifications?
Company operations that contain flammable gases or dust require zone classifications for safety measures. These include:
- Oil and Gas: Businesses operate refineries together with drilling sites and maintain fuel storage facilities.
- Chemical Manufacturing: Processing plants, together with laboratories that contain volatile chemicals, belong to this sector.
- Mining: Explosive gases and dust are present in mining operations at specific underground locations.
- Pharmaceuticals: Manufacturing units handling fine powders.
- Food Processing: Facilities that handle flour and sugar, and grain dust belong to this category.
Frequently Asked Questions About Zone Classifications
1. Does the higher danger level of Zone 0 exceed the risk levels found in Zone 2?
A high-risk Zone 0 contains explosive gas throughout the area, while Zone 2 poses low risk since gas concentrations only exist briefly.
2. What procedure should I use to identify the suitable zone category for my work environment?
Safety professionals must conduct an assessment of flammable substance levels to establish proper zoning requirements.
3. Which equipment is appropriate for working in Zone 1?
The area requires only flame-proof or intrinsically safe equipment that holds certification for Zone 1.
4. Can Zone 22 still be dangerous?
Limited explosions remain possible, although the original risk level is reduced as long as maintenance remains proper.
5. What are ATEX?
International standards named ATEX establish security rules for equipment inside dangerous areas.
Conclusion
Safety requirements in operations that deal with flammable gases and dust need specific zone classifications for proper safety control. The knowledge of Zone 0, 1, 2, 20, 21, 22 distinctions allows businesses to select proper protective equipment, which minimizes safety risks and satisfies safety regulations.
What does ATEX Zone 22 mean?
Zone 22 is an area where a combustible dust cloud is unlikely during normal operation and, if it does occur, persists only for a short time.
What is the difference between ATEX Zone 21 and Zone 22?
Zone 21 has a dust cloud likely during normal operation, while Zone 22 has one only rarely and briefly, so Zone 21 needs higher-category equipment.
What are ATEX Zones 20, 21 and 22?
They are the dust equivalents of gas Zones 0, 1 and 2, classifying how often a combustible dust cloud is present in the area.
Which zone is the most dangerous?
Zone 0 for gas and Zone 20 for dust are the most hazardous, because an explosive atmosphere is present continuously or for long periods.
Industrial Applications & Real-World Use Cases
In hazardous industrial environments such as oil refineries, petrochemical plants, offshore platforms, and mining operations, reliable communication is a critical safety requirement. Workers in Zone 1 and Zone 21 classified areas face constant exposure to flammable gases, vapors, and combustible dust. Any electronic device used must be intrinsically safe to prevent ignition.
Oil & Gas Operations
Field engineers on drilling rigs, well pads, and production platforms rely on ATEX certified devices for work order management, real-time communication with control rooms, digital permit-to-work systems, and photographic documentation. Our devices are deployed across ADNOC, Saudi Aramco, KOC, KNPC, ONGC, Petrobras, and Shell facilities worldwide.
Refinery & Petrochemical Safety
Process safety management requires continuous communication between operators, maintenance technicians, and HSE personnel. ATEX phones enable instant push-to-talk during turnarounds, emergency responses, and inspection rounds. Explosion-proof tablets allow viewing P&IDs and digital checklists in the field.
Offshore Platform Operations
Offshore environments present salt spray corrosion, extreme weather, and limited charging infrastructure. Our IP68-rated devices withstand these conditions while maintaining Zone 1 certification for crane coordination, emergency mustering, and helicopter manifesting.
Safety Compliance Standards
- ATEX Directive 2014/34/EU — European explosive atmospheres standard
- Ex ia IIC T4 Gb — Zone 1 intrinsic safety for gas groups
- Ex ia IIIC T135°C Db — Zone 21 dust protection
- IP68 — Dust and water protection
- MIL-STD-810H — Military-grade durability
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Related ATEX Products & Resources
Explore our range of ATEX-certified devices for hazardous areas:
Selecting the Right Device for Your Operation
Choosing the correct explosion-proof device depends on your specific operational requirements, environmental conditions, and workflow needs. Here are the key factors to consider when evaluating intrinsically safe communication equipment for your facility:
For Field Operators and Technicians
Personnel performing daily rounds, equipment inspections, and maintenance tasks benefit from compact phones with long battery life and rugged construction. The EX72 Plus delivers excellent balance between size, durability, and Zone 1 certified functionality for hands-on field work.
For Engineers and Supervisors
Professionals who need to reference drawings, access CMMS systems, review data trends, and manage digital permits require larger displays and more processing power. The EX 101 Ultra and INFINITY EX 100 PRO provide the performance needed for these demanding tasks while maintaining full ATEX certification.
For Tablet-Based Workflows
Operations transitioning to digital permit-to-work, electronic logbooks, or tablet-based inspection systems need larger screen formats. The TL110 5G Tablet provides a desktop-class experience in a Zone 1 rated package, ideal for control room extensions, field engineering, and supervisor walkdowns.
Key Selection Criteria
- Zone classification of your operating environment (Zone 1 gas and/or Zone 21 dust)
- Temperature range at your facility (our devices operate from minus 20 to plus 60 degrees Celsius)
- Battery duration needed for your shift length (8, 12, or 16 hour shifts)
- Application requirements such as SAP, push-to-talk, camera quality, or GPS accuracy
- Network compatibility with your facility communications infrastructure
Contact our team for a personalized device recommendation based on your specific operational requirements.
Related Guides & Certified Devices
For a deeper look at the most commonly cited classification, see our Zone 1 Hazardous Area guide. If you need certified devices for a specific site, browse ATEX phones for Qatar operations or our full range of Zone 1/2 certified phones and tablets.