Regulations 51–53: WHS Hazardous Atmospheres and Flammables

Regulatory citation: Model Work Health and Safety Regulations, Chapter 3, Part 3.2, Divisions 8–9, Regulations 51–53 (Hazardous atmospheres; storage of flammable or combustible substances)

What Are the WHS Hazardous Atmosphere Regulations?

Regulations 51 to 53 of the model WHS Regulations cover atmospheres that could cause fire, explosion or asphyxiation, and the storage of flammable and combustible substances. Regulation 51 defines a hazardous atmosphere and requires PCBUs to manage the risks. Regulation 52 deals with ignition sources in a hazardous atmosphere. Regulation 53 requires flammable and combustible substances to be kept to the lowest practicable quantity.

These rules apply in any workplace, not only in confined spaces. Typical settings include spray painting booths, fuel stores, flour and grain handling, battery charging areas and workshops using solvents or gas cylinders.

Why These Regulations Matter

Fires and explosions in workplaces can kill or injure many people at once and destroy plant and buildings. Oxygen-deficient or oxygen-enriched air can also cause collapse or make materials burn far more readily. Managing the atmosphere, ignition sources and the amount of fuel on site addresses all three sides of the fire triangle.

Core Obligations

1. Know What a Hazardous Atmosphere Is (r51(2))

An atmosphere is hazardous if it does not have a safe oxygen level, if the concentration of oxygen increases the risk of fire, if the concentration of flammable gas, vapour, mist or fumes exceeds 5% of the lower explosive limit (LEL) for the substance, or if combustible dust is present in a quantity and form that would result in a hazardous area.

2. Check Oxygen Levels Against the Safe Range

Safe Work Australia's model code of practice on confined spaces describes a safe oxygen level as an oxygen content in air of between 19.5% and 23.5%. Oxygen levels outside that range can cause loss of consciousness or increase fire risk.

3. Manage Hazardous Atmosphere Risks (r51(1))

A PCBU must manage risks to health and safety associated with a hazardous atmosphere at the workplace in accordance with Part 3.1. That means identifying hazards, eliminating risk so far as is reasonably practicable, then minimising it using the hierarchy of control, and maintaining and reviewing the controls.

4. Identify Hazardous Areas

Safe Work Australia guidance describes a hazardous area as an area in which an explosive atmosphere is present, or may be expected to be present, in quantities that need special precautions for equipment and potential ignition sources. Electrical equipment and other plant in these areas should suit the area classification.

5. Control Ignition Sources (r52)

A PCBU must manage risks associated with an ignition source in a hazardous atmosphere in accordance with Part 3.1. Ignition sources include open flames, hot surfaces, sparks from tools or electrical equipment, and static discharge. This does not apply where the ignition source is part of a deliberate process or activity at the workplace.

6. Keep Flammable Stock to a Minimum (r53)

If flammable or combustible substances are kept at a workplace, the PCBU must ensure they are kept at the lowest practicable quantity for the workplace. This includes flammable and combustible liquids, including waste liquids, in containers, whether empty or full, and gas cylinders, whether empty or full.

7. Link to Other Requirements

Hazardous chemicals rules in Part 7.1 add specific duties on storage, separation, placarding and fire protection for many flammable substances. Confined space rules in Part 4.3 add entry permit and atmosphere testing requirements where a hazardous atmosphere is in an enclosed space.

Common Compliance Approaches

Area Classification and Equipment Selection

Have a competent person classify hazardous areas and confirm that electrical equipment and plant in those zones is suitable and maintained.

Housekeeping and Stock Control

Order flammable liquids in smaller quantities, return or dispose of empty containers and cylinders promptly, and clean up combustible dust before it accumulates.

Hot Work Permits

Use a permit system for welding, grinding and cutting near flammable materials, with gas testing, removal of combustibles and a fire watch.

Example: Hazardous Atmosphere Controls in Practice

A furniture finishing business uses solvent-based lacquers in a spray booth. It confirms the booth extraction keeps vapour well below 5% of the LEL during spraying, and a competent person classifies the booth and nearby mixing room as hazardous areas. Standard light fittings in the mixing room are replaced with equipment rated for the zone. The business cuts the lacquer it keeps on site from a month's supply to one week's, and removes empty drums and spent aerosol cans each Friday. Hot work near the booth now needs a permit.

Related regulations: WHS hazardous chemicals, WHS confined spaces, WHS hierarchy of controls.

Note: This summary is based on the model WHS laws published by Safe Work Australia. The model laws only have legal effect once a jurisdiction adopts them. Most states and territories have adopted them with some variations, which can include different wording or regulation numbers, while Victoria has not adopted the model WHS laws and has its own OHS laws. Amendments to the model laws apply only once a jurisdiction adopts them. Always check the legislation and codes of practice that apply in your jurisdiction.

Frequently Asked Questions

What percentage of the LEL makes an atmosphere hazardous?

Under regulation 51, an atmosphere is hazardous if the concentration of flammable gas, vapour, mist or fumes exceeds 5% of the lower explosive limit for the substance.

Do empty containers count toward flammable storage?

Yes. Regulation 53 covers flammable and combustible liquids in containers whether empty or full, and gas cylinders whether empty or full, because residues and vapour can still burn or explode.

Does regulation 52 ban all ignition sources?

No. It requires the risks of ignition sources in a hazardous atmosphere to be managed. It does not apply where the ignition source is part of a deliberate process or activity at the workplace.