A hazardous area is a three-dimensional space where an explosive atmosphere is present, or may be present, in quantities that require precautions for electrical and mechanical equipment. In practical terms, that atmosphere may be made up of flammable gas, vapour, mist, combustible dust, fibres or flyings mixed with air.

For an explosion or fire to occur, there needs to be fuel, oxygen and a suitable ignition source. Hazardous area work is about understanding where the fuel and air mixture can occur, how often it can occur, how long it may remain, and what controls are needed so equipment does not become the ignition source.

The classification gives the site a shared reference point. It defines the zone, the relevant gas or dust group, the temperature requirements and the extent of the hazardous area. From there, equipment must be selected, installed, inspected, maintained and recorded in a way that matches the classification.

This matters most on live sites where plant changes over time. A new pump, a modified chute, a different chemical, an unrecorded like-for-like replacement, a change to ventilation or a build-up of dust can all affect the assumptions behind the classification. If the documentation does not move with the plant, the site can be left with records that no longer describe the real installation.

Where Hazardous Areas Occur in Mining

In coal mining, hazardous areas can occur around coal handling and processing infrastructure where methane, flammable vapours or combustible coal dust may be present. Common examples include ROM dump stations, breaker stations, crushers, sizers, bins, transfer stations, conveyor discharge points, sampling stations, surge bins, train load-out systems, reclaim areas and stockpiles.

Reagent and fuel areas can also introduce flammable liquid and vapour hazards. MIBC storage and injection points, diesel storage, tanker unloading points, tank vents, pumps, valves, flanged connections and bunded compounds all need to be considered when site conditions allow vapours to form and collect.

Metalliferous mines and mineral processing plants can have similar issues around fuel farms, chemical storage, solvent use, reagent systems, crushing and screening circuits, dust collection systems, workshops and battery facilities. The material changes, but the question is the same: can a flammable or combustible atmosphere form under normal or foreseeable operating conditions?

Hazardous areas also appear outside mining, including oil and gas, fuel storage and dispensing, manufacturing, spray booths, distilleries, food processing, agriculture and energy projects. Those industries have different processes and substances, although the classification still comes back to release sources, ventilation, operating conditions and ignition risk.

Gas, Vapour and Combustible Dust

In mining, flammable gases and vapours may be associated with methane from underground workings, MIBC and other reagents, diesel systems, fuel storage, flammable liquid handling and some maintenance activities. Vapours can be released through vents, transfer points, open connections, spills, leaks, fittings or tank unloading activities.

Combustible dust is often the area that gets underestimated. Coal dust, metal powders and process dusts can form explosive atmospheres when they become airborne at the right concentration. On coal handling systems, this can occur around enclosed chutes, transfer points, dump hoppers, breakers, crushers, bins, sample stations and poorly controlled conveyor discharge points.

Dust layers need their own attention. A settled layer can be disturbed and become a dust cloud, or it can sit on equipment surfaces and introduce a temperature risk if the surface gets hot enough. That is why housekeeping, dust suppression, ventilation and maintenance are not side issues. They can be the controls that stop a dust hazard from growing into something far more serious.

Ignition sources include arcing contacts, hot surfaces, static electricity, incorrect cable entries, damaged equipment, unsuitable portable equipment and maintenance activities such as hot work. In a classified area, equipment selection and installation are only part of the control. The equipment also has to remain suitable for the environment during operation, inspection and maintenance.

Understanding Hazardous Area Zones

Zones describe how likely an explosive atmosphere is to be present and how long it may remain.

Gas and Vapour

ERZ 0 / Zone 0
An explosive gas atmosphere is present continuously, frequently or for long periods.

ERZ 1 / Zone 1
An explosive gas atmosphere is likely to occur occasionally during normal operation.

NERZ / Zone 2
An explosive gas atmosphere is unlikely to occur during normal operation. If it does occur, it is expected to exist for a short period.

Combustible Dust

Zone 20
An explosive atmosphere in the form of a combustible dust cloud is present continuously, frequently or for long periods.

Zone 21
An explosive dust atmosphere is likely to occur occasionally during normal operation.

Zone 22
An explosive dust atmosphere is unlikely during normal operation and, if it does occur, is expected to remain for a short period.

What the Zone Determines

The zone gives the starting point for selecting equipment, but it does not answer every question on its own.

A suitably qualified person should confirm the equipment against the specific area classification, including the substance involved, gas or dust group, temperature class or maximum surface temperature, equipment protection level, protection technique, ambient conditions and any specific conditions of use.

Installation then needs the same level of care. Appropriately qualified electricians should install hazardous area equipment and complete the required initial detailed inspections before the equipment is energised. Glands, cable entries, enclosures, accessories, wiring methods, earthing and bonding all affect whether the intended explosion protection is maintained.

The Standards That Apply

The AS/NZS 60079 series provides the main technical framework in Australia, supported by mining legislation, recognised standards and site-specific safety and health management systems where they apply.

AS/NZS IEC 60079.10.1
Classification of areas where flammable gas or vapour hazards may arise.

AS/NZS 60079.10.2
Classification of areas where combustible dust hazards may arise.

AS/NZS 60079.14
Covers the design, selection, installation and initial inspection of electrical installations in explosive atmospheres. This is the key standard for installers because it sets out how hazardous area equipment should be selected and installed so the required type of protection is maintained. It is also important for end users because it helps confirm that the installation is suitable before equipment is put into service.

AS/NZS 60079.17
Covers the inspection and maintenance of electrical installations in explosive atmospheres. This is especially important for end users because it supports the ongoing management of hazardous area equipment after installation, including inspection grades, inspection intervals, defect management, records and maintenance requirements.

The rest of the AS/NZS 60079 series supports the broader hazardous area framework, including area classification, equipment construction, equipment testing, individual protection techniques and specific installation requirements. AS/NZS 3000 still applies to electrical installations more generally, while mining operations may also need to consider AS/NZS 3007, AS/NZS 5368 and recognised standards depending on the site, commodity and regulatory framework.

Queensland Requirements

Queensland requirements depend on the type of site and the legislation that applies to it.

For many Queensland workplaces, section 221 of the Electrical Safety Regulation 2013 requires an electrical installation in a hazardous area to be inspected by an accredited auditor before it is connected to electricity for the first time, or reconnected. Section 221A provides limited exemptions for replacement with similar equipment, although those exemptions do not extend to switchboards, cables or wires.

Some Queensland mining and resource operations sit outside that electrical safety regulation pathway and have obligations under their own legislation. Coal mines, metalliferous mines, quarries and petroleum operations may need to manage hazardous area risks through their safety and health management system, site standards, recognised standards, statutory roles and mine-specific procedures.

Keeping the Picture Current

Hazardous area classification drawings, equipment registers, inspection records, maintenance records and verification dossier information should describe the installation as it actually exists.

That sounds obvious until a site has been through several projects, shutdowns, urgent repairs and small modifications. Drawings can fall behind, equipment certificates can be missing, inspection findings can remain open, and change records can be held in different places by different teams.

Sites do not need perfect paperwork for the sake of paperwork. They need a practical way to show what the hazardous areas are, what equipment is installed, why that equipment is suitable, who inspected it, what changed and what needs attention. When equipment, processes, ventilation, materials or operating conditions change, a change management process should trigger a review of the hazardous area documentation.

Where HazardProof Fits

HazardProof supports site, engineering and project teams with hazardous area classification and design, accredited auditing, inspections, verification dossier development and review, intrinsic safety assessments, remediation planning and compliance close-out.

We work across underground coal, metalliferous mining, oil and gas, distilleries, spray booths, manufacturing and other industrial environments. The technical work matters, but so does the way it is delivered. Our focus is clear findings, practical recommendations and records your team can actually use.