ATEX Zones are critical for ensuring safety in environments where flammable gases or vapours may be present. At OTECSA, we help organisations identify and understand their hazardous zones—Zone 0, 1, and 2—so they can select the correct equipment, prevent ignition sources, and comply with legal safety standards. Hazardous Area Classification (HAC) plays a crucial role in managing explosion risks in workplaces where flammable gases or vapours may be present.
One of the most frequently asked questions we hear is: What’s the difference between ATEX Zones 0, 1, and 2—and how does this impact equipment requirements?
What Are ATEX Zones?
ATEX zones classify areas based on the likelihood of a flammable atmosphere being present due to gases or vapours. These zones guide what type of equipment can be safely used without becoming an ignition source. They are defined through a Hazardous Area Classification (HAC) study, which assesses the frequency of flammable releases and the ventilation in the area.
- Zone 0: An area where a flammable atmosphere is present continuously or for long periods.
- Zone 1: An area where a flammable atmosphere is likely to occur in normal operation.
- Zone 2: An area where a flammable atmosphere is not likely to occur in normal operation, and if it does, will exist only for a short time.
Understanding which zone applies is key to selecting ATEX-rated electrical and mechanical equipment suitable for safe operation.
Grades of Release and Their Role in HAC
To determine which zone applies, engineers begin by identifying the grade of release—essentially, the likelihood that a flammable release will occur:
- Continuous: Release expected frequently or for extended durations
- Primary: Release expected periodically during normal operation
- Secondary: Release unlikely during normal operation and brief in duration
Examples include:
- Continuous: Inside equipment handling flammable liquids above their flash point
- Primary: Vapours escaping from routinely opened hatches
- Secondary: Intermittent venting from relief valves
The grade of release, combined with ventilation conditions, determines the zone extent and dilution level, which are used to map safe equipment use.
Why Zone Designation Matters for Equipment Selection
The ATEX zone influences not only where you can place equipment but what kind of equipment can be installed. Electrical and mechanical systems must be constructed to prevent sparks, overheating, or other ignition risks. For instance, Zone 0 environments may require intrinsically safe equipment, while Zone 2 may permit less stringent protection methods.
Equipment that is incorrectly rated can pose a serious hazard, while over-zoning (selecting more expensive, high-spec equipment than necessary) can lead to unnecessary capital costs. This is why a well-executed HAC study is critical—it strikes the right balance between safety and cost-efficiency.
Taking a Pragmatic Approach to Hazardous Area Classification
A thorough HAC study depends on accurate data and sound engineering judgement. British Standard BS EN 60079-10-1 provides guidance on dilution and zone extent calculations, but the interpretation often requires practical experience. Overly conservative zoning can drive up equipment costs, while under-zoning can compromise safety.
At OTECSA, we bring sector-specific experience to help you apply zoning standards appropriately—supporting smarter decisions from the design stage through to operation. Whether you’re planning new equipment or reviewing an existing site, we offer a clear, pragmatic approach to Hazardous Area Classification and ATEX compliance.
Want to learn more about zoning requirements and ATEX-rated equipment? Contact our team at OTECSA Consulting for expert support in conducting a HAC study.