Hazardous Areas Classification (HAC)

HAZARDOUS AREAS CLASSIFICATION

Hazardous Areas Classification (HAC) defines where explosive atmospheres may occur and how far they extend.

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Hazardous Areas Classification (HAC)

Hazardous Areas Classification (HAC) defines where explosive atmospheres may occur and how far they extend. The resulting zones form the basis for equipment selection, ignition source control, and safe work practices.

Studies are carried out using IEC 60079-10-1 for gases/vapours and IEC 60079-10-2 for combustible dusts. With support from our specialists, inputs are turned into clear, defensible zoning decisions that different disciplines can work with.

Typical outputs include area classification drawings, zone schedules, and a concise Basis of Classification that can be shared across engineering, HSE, and operations. The approach is aligned with both EU/UK (ATEX/DSEAR/IEC) andNorth American (NEC/NFPA) frameworks, so the outcome is suitable for both internal use and external audit.

HAZARDOUS AREAS CLASSIFICATION Background and Regulatory Context

In the EU, ATEX 1999/92/EC requires employers to assess explosion risks and classify places into zones. The results form part of the Explosion Protection Document and must be in place before operation.

Equipment installed in those zones must comply with ATEX 2014/34/EU product requirements. HAC therefore directly informs the required equipment category/EPL and temperature class.

The technical zoning basis for explosive atmospheres is given in:

  • IEC 60079-10-1 for explosive gas atmospheres (gases/vapours), and
  • IEC 60079-10-2 for explosive dust atmospheres.

In the UK, DSEAR makes hazardous area classification and zone documentation a legal duty. In North America, zoning and equipment selection follow NFPA 70 (NEC) Articles 500/505/506, supported by NFPA 497 (gases/vapours) and NFPA 499 (dusts).

HAC is therefore a mandatory and recognized element wherever explosive atmospheres may occur, across both regulators and standards bodies.

How HAC Works – Step by Step

  1. Inputs and Planning

The work starts with a clear view of scope and context:

  • Agreeing scope, sites, and substances to be covered.
  • Collecting PFDs/P&IDs, layouts, ventilation data, operating modes, and maintenance context.
  • Confirming which framework applies: ATEX/IEC or NEC/NFPA.
  • Defining review cadence, roles, and delivery format.

This stage ensures that classification effort focuses on the correct areas, substances, and regulatory framework.

  1. Gas/Vapour HAC (IEC 60079-10-1)

For flammable gases and vapours, the classification follows the IEC method:

  • Identifying sources of release and assigning release grades (continuous, primary, secondary).
  • Assessing the degree and availability of ventilation to determine Zones 0/1/2.
  • Sizing zone extents using recognized methods and documenting assumptions.
  • Recording gas group (IIA/IIB/IIC) and temperature class for equipment selection interfaces.

The result is a set of gas/vapour zones with traceable reasoning and clear links to equipment requirements.

  1. Dust HAC (IEC 60079-10-2)

For combustible dusts, the focus shifts to cloud formation and deposits:

  • Evaluating conditions for dust cloud formation and layering.
  • Assigning Zones 20/21/22 and defining extents based on enclosure, handling, and housekeeping.
  • Using material data and, where needed, test methods in line with ISO/IEC 80079-20-2.

This produces a consistent view of dust zones that can be used across projects and operations.

  1. Material Properties and Data Support

Reliable material data underpins the classification:

  • For gases/vapours, referencing IEC 60079-20-1 data and methods.
  • For dusts, referencing ISO/IEC 80079-20-2 (e.g., MIE, Kst test methods).

Where data is not directly available, our team highlights assumptions and any recommendations for further testing.

  1. Equipment Selection Interface

The zoning outputs are translated into clear guidance for equipment selection:

  • For EU/UK, mapping zones to EPL (Ga/Gb/Gc; Da/Db/Dc) and providing guidance in line with IEC 60079-14.
  • Stating temperature class, gas/dust group, and any implications for mechanical equipment.
  • For North America, providing the equivalent NEC Class/Division/Zone view and linking to NFPA 497/499 for device selection.

This interface allows engineering and procurement teams to apply the classification consistently.

  1. Documentation and Handover

The final step is to package the outputs in a way that is easy to use and audit:

  • Area classification drawings, showing zones, extents, and key notes.
  • Zone schedules and a Basis of Classification narrative.
  • Mark-ups for P&IDs and plot plans, plus a change-trigger checklist.
  • Revalidation timing aligned with your PSM/MOC or stage-gate plan.
  • Briefings so engineers, HSE, and operations work from one shared picture.

RISK management
RISK assessment

Deliverables and Client Value

Deliverables

  • HAC Report and Basis of Classification.
  • Area classification drawings (zones, extents, and notes).
  • Zone schedule with EPL/category, group, and temperature class.
  • EU/UK equipment selection guidance (IEC 60079-14 interface).
  • NEC mapping plus NFPA 497/499 references.
  • Action register and executive brief to support audits and permits.
  • Revalidation plan and change triggers.

Client Value

  • Clear, defensible zoning recognized by auditors and regulators.
  • Faster, safer equipment selection and work control.
  • Fewer design changes and smoother commissioning.
  • A common risk picture across engineering, operations, and HSE.
  • Confidence that the classification method follows recognized practice.

Our Process Safety and Functional Safety specialists will provide an initial consultation and support your organisation through SIL Verification — from planning and data selection to a practical, compliant verification package.

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