Hazardous Area Classification

Hazardous Area Classification (HAC)

Classify clear, defensible hazardous-area zoning for flammable gas/vapour and combustible dust atmospheres.

We align the classification to the AS/NZS IEC 60079 series (e.g., AS/NZS IEC 60079.10.1) and provide practical drawings + a classification dossier that contractors can build to, and operations teams can maintain.

Key outcomes

Remove ambiguity around where the zone starts/stops so equipment and installation requirements are unambiguous
Define EPL requirements (Ga/Gb/Gc or Da/Db/Dc) and any special conditions of use
Establish the compliance baseline for Management of Change (MOC) and periodic review

What we do (scope inclusions)

Desktop review of process info (P&IDs, layouts, SDS, operating conditions) and existing HA documentation (if available)
Site walkdown / data capture to confirm release sources, ventilation paths, bunding/drainage, and equipment placement
Identify release sources + grades of release; evaluate ventilation effectiveness and dispersion
Determine zone type and extent (gas/vapour: Zone 0/1/2; dust: Zone 20/21/22) and document assumptions/limitations
Produce zone drawings and a classification report suitable for regulator/insurer/project handover

Typical deliverables

HAC report (basis, assumptions, zone rationale, references)
Zone drawings (CAD/PDF) with extents (and elevations/sections where required)
Substance & release source register
EPL requirements table for each zone + equipment requirements guidance
Gap list / actions register (documentation gaps, plant changes, equipment issues observed)

Engagement options

HAC Gap Assessment (desktop + targeted walkdown)
Full HAC (walkdown + complete classification dossier)
HAC Update / MOC Review (update drawings/assumptions after plant changes)

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Other HADC Services

Hazardous Area Design

Hazardous Area Audits

Hazardous Area Classification FAQs

Do you classify both gas/vapour and dust hazardous areas?

Do you classify both gas/vapour and dust hazardous areas?
Yes, gas/vapour (Zone 0/1/2) and dust (Zone 20/21/22), including sites with both hazards. We confirm zone extents and the required EPL for compliant equipment selection.

Can you work from an existing classification dossier?

Can you work from an existing classification dossier?
We can validate what you have, update it after changes (MOC), and issue a gap/action list where assumptions or site conditions don’t match “as-operated”.

Do you provide CAD drawings?

Do you provide CAD drawings?
Yes, zone drawings issued as PDF and DWG/CAD where needed. We can also mark up your existing drawings to suit your document control system.

What if our site data is incomplete?

What if our site data is incomplete?
That’s common. We combine available documents with a site walkdown to confirm release sources and ventilation. Any remaining unknowns are captured in a clear assumptions + information request list, so the outcome remains defensible.

How often should classification be reviewed?

How often should classification be reviewed?
Whenever there’s a change that could affect the hazardous atmosphere (materials, process conditions, ventilation, layout). Many clients also adopt a 3–5-year baseline review, depending on site risk and change frequency.

Why RelyOn?

• Led by industry-recognised HACD engineers

• Independent, defensible engineering advice

• Deep experience across renewables, BESS, hydrogen & industrial assets

• Integrated with broader electrical safety & compliance services

Speak to our Hazardous Areas Team