ATEX / IEC 60079-10-1 / IEC 60079-10-2 Methodology

ATEX / IEC 60079 Hazardous Area Classification

Zone 0, 1, 2 and Zone 20, 21, 22 classification using a release-source, ventilation/dilution, material-property, and equipment-layout basis that supports IEC design and ATEX workplace documentation.

HazBasis performs Zone-based Hazardous Area Classification for projects using IEC 60079 and for facilities that need area-classification support within an ATEX workplace framework. For gas and vapor hazards, the technical methodology is based on IEC 60079-10-1. For combustible dust hazards, the current IEC 60079-10-2 methodology is applied.

The study identifies where explosive atmospheres can occur, how often they can be expected, how far they may extend, and what gas/dust group or temperature-related information must be carried forward into equipment selection and installation design.

ATEX and IEC Are Related—but They Are Not the Same Thing

This distinction is important for technically correct project documentation. ATEX is the European regulatory framework for explosive atmospheres; IEC 60079 is a family of technical standards used internationally for explosion-protected electrical systems and area classification.

Current technical basis verified August 2026: IEC 60079-10-1:2020 is the current gas/vapor area-classification edition; IEC 60079-10-2:2026 was published June 29, 2026 for explosive dust atmospheres. Project-specific EN adoptions, national transposition of ATEX, owner standards, and authority requirements must also be confirmed.

IEC Zone Classification at a Glance

IEC 60079-10-1 Methodology — Explosive Gas Atmospheres

IEC 60079-10-1 is not simply a Zone-definition table. The classification is developed from the relationship between the source of release, the release conditions, and the ability of ventilation or dilution to control the resulting flammable cloud.

1. Identify flammable substances and process states — Compile flammable gas/vapor properties and actual operating temperature, pressure, composition, phase behavior, and containment conditions.

2. Identify sources of release — Locate points from which flammable gas or vapor can be released to atmosphere, including vents, seals, sampling points, drains, open transfers, relief outlets, equipment openings, and credible leakage sources.

3. Assign grade of release — Classify the source as continuous, primary, or secondary based on how often and under what operating conditions release is expected.

4. Determine release characteristics — Evaluate or calculate the release rate/characteristic using pressure, temperature, opening geometry, fluid properties, evaporation/flashing behavior, and other scenario-specific parameters.

5. Evaluate ventilation and dilution — Assess air movement, enclosure, natural/mechanical ventilation, dilution capability, ventilation availability, and locations where gas/vapor can accumulate.

6. Determine zone type — Use the grade of release together with ventilation/dilution performance to determine whether the resulting location is Zone 0, Zone 1, Zone 2, or potentially non-hazardous under the documented basis.

7. Determine zone extent — Establish the horizontal and vertical extent based on the release characteristic, gas/vapor behavior, ventilation, obstacles, openings, and geometry.

8. Carry forward equipment-selection data — Document gas group, temperature-related information, and other classification notes needed by the electrical/equipment design team.

Grades of Release — Why They Matter

Ventilation and Dilution Are Part of the Classification — Not Afterthoughts

A Zone boundary can change significantly depending on whether the release occurs outdoors, inside a well-ventilated building, within a partially enclosed skid, below grade, or near a ceiling where a light gas can collect. HazBasis documents the ventilation assumptions that support the classification rather than treating “indoors” or “outdoors” as sufficient engineering conclusions.

• Natural vs. mechanical ventilation and its availability.
• Local exhaust and capture effectiveness near the release source.
• Room volume, obstructions, equipment congestion, pits/trenches, roof pockets, and enclosed skids.
• Gas/vapor density and buoyancy behavior.
• Potential background concentration when multiple or persistent release sources exist.
• Failure modes of mechanical ventilation where classification depends on ventilation.

IEC 60079-10-2 Methodology — Explosive Dust Atmospheres

IEC 60079-10-2 addresses explosive dust clouds and combustible dust layers. These are related but different hazards. A layer can create a hot-surface/fire hazard and can become a secondary source of dust cloud if disturbed; the area-classification review should therefore evaluate both cloud-release behavior and layer accumulation.

1. Confirm combustible dust hazard — Identify the powder/dust and establish whether it can form an explosive dust atmosphere under relevant process conditions.

2. Identify sources of dust release — Map normal and abnormal release points at mills, mixers, sieves, dryers, collectors, transfers, bag dumps, discharge points, packaging, conveying, and access openings.

3. Assign grade of dust release — Classify sources based on whether dust release is continuous/frequent, primary during normal operation, or secondary under abnormal/infrequent conditions.

4. Evaluate cloud formation and dispersion — Assess dustiness, release quantity, drop height, transfer energy, local exhaust, enclosure, air movement, and the likelihood that a dispersed dust cloud can reach an explosible concentration.

5. Evaluate dust layers separately — Assess where dust can settle, layer thickness/extent, housekeeping, elevated surfaces, cable trays, equipment ledges, and whether layers can be disturbed into a cloud.

6. Determine Zone 20/21/22 — Assign the Zone based on the likelihood and persistence of explosive dust atmospheres and the release-source basis.

7. Establish zone extent — Determine the boundary around the dust release source or equipment based on dispersion, containment, ventilation/air movement, housekeeping, and physical geometry.

8. Document dust group and temperature inputs — Provide the dust group and ignition-temperature information needed for downstream equipment selection and maximum surface-temperature evaluation under the applicable installation/product standards.

Dust Groups Under the IEC Framework

ATEX Workplace Zoning and Equipment Categories

For EU/EEA projects, workplace zoning under Directive 1999/92/EC supports the employer’s explosion-risk controls and Explosion Protection Document. The equipment placed on the market is addressed separately by Directive 2014/34/EU. The Zone classification therefore becomes a key input to selecting equipment with an appropriate ATEX category and explosion-protection marking.

*Simplified relationship for non-mining equipment; final equipment selection must follow the applicable ATEX/EN/IEC product and installation requirements, certification/marking, and national implementation.

Gas Group, Dust Group, Temperature and EPL/Category Coordination

The Zone number alone is not enough to specify equipment. A complete classification basis should carry forward the material group and temperature information required for the electrical/equipment design team.

• Gas/vapor group (for example IIA, IIB, IIC as applicable).
• Dust group (IIIA, IIIB, IIIC as applicable).
• Temperature class or maximum permissible surface-temperature basis as required by the applicable equipment/installation standard.
• Zone designation and extent.
• Equipment Protection Level (EPL) / ATEX category coordination where relevant to the project basis.
• Any special environmental, ingress, or process conditions that affect equipment suitability but are outside the zone designation itself.

Typical IEC / ATEX Classification Scenarios

What HazBasis Delivers for IEC / ATEX Projects

• IEC / ATEX Hazardous Area Classification report with standard basis, process description, material properties, release-source methodology, ventilation/dilution assumptions, zone decisions, and limitations.
• Gas/vapor and/or dust release-source schedule showing source grade, zone classification, extent, and material-group information.
• Zone drawings showing Zone 0/1/2 and/or Zone 20/21/22 plan and elevation boundaries.
• Technical inputs to the Explosion Protection Document or project explosion-protection basis, where that support is within scope.
• Equipment-selection basis inputs for coordination with the electrical engineer, Ex equipment specialist, EPC, manufacturer, and owner.
• Reviewer, client, insurer, or authority comment support.

When Testing Is Needed

IEC classification quality depends on reliable material data. Published data may be adequate for a pure substance, but custom mixtures, process intermediates, proprietary powders, or material that changes through drying/milling can require testing.

Electrostatic: charge-decay, resistivity, liquid conductivity, FIBC classification, or other electrostatic data when separate ignition-source evaluation is required.

Gas/vapor: flash point, LFL/UFL, autoignition temperature, vapor pressure or other physical-property data where needed.

Dust: explosibility screening, MIE, minimum ignition temperature of dust cloud/layer, resistivity/conductivity, particle size and moisture where relevant.

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