Fire and explosion can have catastrophic consequences. You must control ignition sources such as naked lights, sparks and mobile phones where flammable atmospheres may exist.
Fire and explosion can result in catastrophic consequences, causing serious injuries or death of workers and others, as well as significant damage to property. A person conducting a business or undertaking (PCBU) must prevent the possibility of fire or explosion from an ignition of flammable substances associated with a hazardous area or a hazardous atmosphere.
Section 355 of the Work Health and Safety Regulation 2011 requires specific controls for prevention of fire and explosion associated with hazardous chemicals. A PCBU must ensure an ignition source is not introduced into a hazardous area (from outside or within the space).
Section 52 of the WHS Regulation requires a PCBU to manage risks to health and safety associated with an ignition source in a hazardous atmosphere. With respect to flammable substances, a hazardous atmosphere is an atmosphere where the concentration of flammable gas, vapour, mist, or fumes exceeds 5% of the lower explosive limit (LEL) for the substance. The LEL is equivalent to the lower flammability limit or LFL and may be found in Section 9 Physical and chemical properties in a product's safety data sheet.
A hazardous area is an area (three-dimensional space) in which a flammable atmosphere is or may be expected to be present, and require special precautions for the construction, installation and use of equipment. Examples of hazardous areas are:
- flammable liquid and gas storage tanks and associated equipment (e.g. release points such as vents, fill points, dip points, safety relief devices)
- flammable liquid and gas dispensing equipment (e.g. service stations, depots and airports, LP gas filling stations)
- storage areas for flammable liquids in packages (e.g. warehouses, store rooms, workshops)
- storage areas for flammable gases in cylinders
- mixing and blending vessels for flammable product formulations road and rail tanker loading facilities for flammable liquids and gases
- fume cupboards used for flammable liquids and gases
- laboratory areas where flammable liquids are used and stored
- spray painting booths used for flammable paints and lacquers
- landfill gas (e.g. methane), sewage treatment and sewage pumping plants
- flammable solvent printing processes
- accidental puncturing and spilling contents of containers containing flammable liquids
- application of flammable sealants and adhesives in enclosed areas
- areas around activities generating fine dusts of combustible material (sugar, grain, polymers, dry organic residues).
Wherever flammable liquids, vapours, and gases, and combustible dusts are generated, used, stored and handled, a hazardous area classification should be conducted to determine the extent of applicable exclusion zones for potential ignition sources. Exclusion zones are divided into zone 0, 1, or 2 based on the probability of a flammable atmosphere being present as follows:
- Zone 0 hazardous area is an area where a flammable atmosphere is present continuously or for long periods or frequently
- Zone 1 hazardous area is an area where a flammable atmosphere is likely to occur in normal operation occasionally.
- Zone 2 hazardous area is an area where a flammable atmosphere is not likely to occur in normal operation but, if it does occur, it will exist for a short period only.
Once hazardous areas and applicable zones are identified, potential ignition sources can be identified and either eliminated or controlled to prevent a fire or explosion. An ignition source provides a source of energy sufficient to ignite a flammable atmosphere. Examples of ignition sources include:
- naked flames, smoking, pilot lights
- portable electrical equipment such as tools, radios, and fans
- fixed electrical systems and powered circuits with potential for arcs, sparks, short circuits (see additional note below for further info on connecting or reconnecting electrical equipment in a hazardous area)
- hot work activities such as welding, hot-cutting, grinding (can throw hot metal shavings considerable distances)
- operating equipment with combustion engines such as forklift trucks, generators, compressors
- hot surfaces, exhaust pipes, hot flues and ducts and frictional heating
- mechanical sparks from impacts, e.g. lawn mower blades striking a rock, forklift tynes on concrete
- static electricity leading to electrostatic discharges generated incidentally or by processes or activities including:
- low conductivity liquids, e.g. liquid hydrocarbons, flowing at high velocity through pipes and associated fittings
- flow of powdered or granular solid materials (particularly non-conducting materials like plastic beads), e.g. moving through shutes and hoppers, and mixing and sieving
- non-conducting drive or conveyor belts in motion
- movement of people when insulated from earth, particularly if wearing clothing of synthetic fibres.
Risk control measures
Key control measures for managing these risks include:
- identifying and managing hazardous areas
- controlling emissions of flammable vapours, gases and mists (see below)
- use of ventilation systems to control vapours during both normal and abnormal conditions (e.g. leak or spill)
- eliminating ignition sources from hazardous areas (see below)
- installing systems to detect leaks of flammable gases or vapours and enable response actions to be taken
- using intrinsically safe or flameproof equipment
- substituting flammable materials for ones that are less flammable or combustible
- ensuring incompatible materials (e.g. oxidizers and oils) are separated or segregated
- reducing quantities of flammable and combustible materials, including items that contribute to the fire load but that are not hazardous chemicals themselves (e.g. wooden pallets, oil)
- ensuring equipment used in handling flammable hazardous chemicals is maintained in accordance with manufacturer's instructions
- adopting good housekeeping practices to minimise accumulation of combustible dusts.
Controlling flammable substance emissions
Accumulation of vapours, gases, mists creates the potential for a hazardous area to exist. Vapour emissions resulting from processes can be minimised by:
- the use of enclosed container and transfer systems and vapour recovery connections
- keeping lids open only for the minimum period required for transfer
- minimising exposed surface areas (e.g. area of spread for leaked or spilled liquid)
- avoidance of splash filling
- minimising the temperature of liquids being processed or transferred
- providing ventilation, e.g. mechanical extraction for all sources of vapour and vent to a safe area.
When heated, the vapour pressure of flammable and combustible materials may increase resulting in higher vapour emissions. Containers of hazardous chemicals should therefore be stored away from sources of heat (e.g. heaters or other heating appliances). Heat may also deteriorate packaging and increase the risk of failure of the container and product loss. Hot surfaces may also exceed a substance's auto-ignition temperature.
Controlling ignition sources
Controlling potential sources of ignition in a hazardous area may be achieved by:
- use of suitably-rated electrical equipment (e.g. intrinsically safe or flame-proof)
- ensuring electrical equipment is effectively maintained where poorly maintained electrical equipment can present a significant risk for example through worn brushes
- ensuring electrical equipment is properly earthed
- ensuring the auto-ignition temperature of the hazardous chemical is considered as some hazardous chemicals may ignite spontaneously above certain temperatures
- implementing administrative controls such as permit systems preventing hot work (for example, welding) in these areas (see below).
Where electrical installations or equipment are required to be located or used in a hazardous area e.g. lighting, mixers and stirrers, pumps, control systems, forklift trucks, detectors, torches etc, these items must be designed and constructed so that they cannot release energy within the hazardous area that is sufficient to cause an ignition. That is, such equipment must be suitably rated for use in a hazardous area.
Such design and construction techniques include 'intrinsically safe' or 'flameproof/encapsulated' equipment. Any equipment designed and constructed to operate within a hazardous area must also be supplied with documentation stating which zone (i.e. 0, 1 or 2) it is suitable to operate within.
It is a PCBU's duty to ensure equipment within a hazardous area is consistent with the zone assigned to the area, i.e., zone 1 rated equipment must only permitted within a zone 1 hazardous area. However, zone 1 or zone 2 equipment is permitted within a zone 2 hazardous area as zone 1 equipment is more conservative than zone 2.
Safe work procedures must also account for any hazardous areas. For example adopting a hot work permit system to conduct maintenance and repair activities (see below).
Controlling static electricity
Static electricity can be created from a range of activities including the transfer of hazardous chemicals. Information on control of static electricity can be found in AS/NZS 1020:1995 The control of undesirable static electricity and includes methods such as earthing and bonding to ensure any build-up of static electricity is dissipated before a hazardous electrical discharge can occur.
Controlling hot work
Hot work is any process involving grinding, welding, brazing, oxy cutting, heat treatment or any other similar process that generates heat or continuous streams of sparks. Undertaking hot work in areas where flammable or combustible chemicals or other materials are present creates a significant risk of fire or explosion. Conducting hot work on containers such as drums, tanks and pipes that have not been properly decontaminated is a common cause of serious incidents. A hot work permit system is a system designed to eliminate or minimise risks from these activities by controlling when and how hot work is undertaken in these areas.
More information on hot work permit systems is available in the following Australian Standards:
- AS 1940:2004 The storage and handling of flammable and combustible liquids
- AS 2865:2009 Confined spaces
- AS 1674.1:1997 Safety in welding and allied processes – Fire precautions
More information on hazardous areas can be obtained from the following Australian Standards:
- AS/NZS 60079.10.1:2009 Explosive atmospheres – Classification of areas – Explosive gas atmospheres (IEC 60079-10-1, Ed.1.0(2008) MOD)
- AS/NZS 60079.10.2:2011 Explosive atmospheres – Classification of areas – Combustible dust atmospheres
The Electrical Safety Act 2002 has requirements for hazardous area electrical installations.
Oxidising agents can contribute to fire and explosion risks. In relation to working with oxidising agents, information can be found in AS4326: The storage and handling of oxidising agents.
Hazardous atmospheres are often associated with confined spaces. More information on hazards and risk controls associated with confined spaces can be found in the Confined Spaces Code of Practice 2011 ().
More Information on controlling fire and explosion risks is available in the Managing risks of hazardous chemicals in the workplace code of practice 2013 (PDF, 1.46 MB).