Qld issues safety alert after four injured in explosion

In November 2021, a worker was seriously injured while three others received minor injuries, following a workplace explosion and fire. Early enquiries indicate that the incident occurred after an ‘extractor’ exploded. This machine is used to extract rosin and turpentine from pine wood chips by spraying hot turpentine over the wood chips in a process known as solvent extraction. For reasons yet to be established, an explosion occurred. Investigations into the incident are ongoing.

Processes that generate heat and flames are sources of ignition. When combined with fuel and oxygen, there’s a risk of fire and explosion. While the greatest risks are with common flammable liquids like petrol, kerosene and ethanol, combustible liquids such as diesel fuel and oils can behave like flammable liquids when they are heated. They may also generate vapours when heated. When confined, these vapours can cause an explosion if ignited. Hot work is any process involving heat treatment, grinding, welding or any other similar process that generates heat. Hot work in areas where flammable or combustible chemicals or other materials are present creates a significant risk of fire or explosion.

Taking steps to manage risks is a condition of doing business in Queensland. Effective risk management starts with a commitment to health and safety from those who manage the business. Using the hierarchy of controls can help persons conducting a business or undertaking (PCBUs) decide how to eliminate and reduce risks in their place of work. The hierarchy of controls ranks types of control methods from the highest level of protection and reliability to the lowest. PCBUs must work through the hierarchy of controls when managing risks, with the aim of eliminating the hazard, which is the most effective control.

Wherever flammable liquids, vapours and gases are generated, used, stored and handled, PCBUs should perform a hazardous area classification 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. A hazardous area is an area in which a flammable atmosphere is or may be expected to be present from time to time, and requires special precautions for the construction, installation and use of equipment, particularly electrical equipment or any other equipment that can produce hot surfaces, arcs or sparks. 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.

A PCBU must, if there is a possibility of fire or explosion in a hazardous area being caused by an ignition source being introduced into the area, ensure the ignition source is not introduced into the area (from outside or within the space). Potential sources of ignition in a hazardous area can be controlled by performing a hazardous area assessment to determine the relevant hazardous area classification and extent of hazardous zones in and around equipment. PCBUs are also advised to ensure that any later changes to the operation or design of equipment associated with a hazardous area are managed with suitable processes that re-assess the hazardous area classifications and zones.

To further mitigate the possibility of fire or explosion in a hazardous area, PCBUs should use suitably rated electrical equipment that is intrinsically safe or flame-proof, and ensure the electrical installation is maintained and that the electrical equipment is properly earthed. PCBUs should also ensure that the auto-ignition temperature of the hazardous chemical is considered as some hazardous chemicals may ignite spontaneously above certain temperatures. Where electrical installations or equipment need to be located or used in a hazardous area (lighting, forklift trucks, torches, etc), these items must be designed and constructed so they cannot release energy within the hazardous area that is sufficient to cause an ignition. Any equipment designed and constructed to operate within a hazardous area must also be supplied with documentation stating in which zone and temperature class that it is suitable to be operated.

PCBUs must also ensure that only licensed electrical workers install, service and maintain electrical equipment associated with hazardous areas. In addition, electrical installations within a hazardous area in Queensland must be inspected by an Accredited Auditor appointed under the Electrical Safety Act prior to the installation being energised. When positioning plant in the workplace, PCBUs are advised to ensure that risks from hot plant, for example molten material and hot gases, can be controlled through restricted access, guarding or insulation. PCBUs should also ensure that there is sufficient space for safe access to the plant for operation, cleaning, maintenance, inspection and emergency evacuation, and that the proximity to other plant does not have a negative effect on operation of the plant or work processes. The plant must also rest on a suitable foundation where required, for example on a floor or other support that ensures the plant is stable and secure.

Engineering controls include mechanical devices that eliminate or minimise the generation of chemicals, suppress or control chemicals, or limit the area of contamination in the event of spills and leaks. They often involve partial enclosure, use of exhaust ventilation or automation of processes. Examples of engineering controls include providing ventilation (mechanical extraction) to vent to a safe area (ventilation systems should be suitable for the types of hazardous chemicals at the workplace), designing plant to relieve and redirect pressure and flame when an explosion occurs, and installing systems to detect leaks of flammable gases or vapours.

Administrative controls should only be considered when other higher order control measures are not practicable, or to supplement other control measures. This can include developing a safe system of work. This includes developing policies and safe work procedures for the use, handling, storage, clean-up and disposal of hazardous chemicals, and implementing safe work procedures to limit ignition sources in hazardous areas. As part of the administrative controls, PCBUs should also consider determining what special skills are required for people who operate the plant or carry out inspection and maintenance. Administrative controls also include the provision of easy-to-understand information, training and instruction to workers, with training to be provided to workers by a competent person.

Arrangements must also be in place to deal with emergencies, including evacuation procedures, containing and cleaning up spills, and first aid instructions. PCBUs must ensure that there is sufficient space for safe access to the plant for maintenance, repair or cleaning activities. Any remaining risk must be minimised with suitable personal protective equipment, such as overalls, aprons, footwear, gloves, chemical-resistant glasses, face shields, respirators and air-supplied respiratory equipment.

Adopting and implementing higher order controls before considering administrative or PPE controls will significantly reduce the likelihood of a similar incident occurring. The control measures used should be reviewed regularly to make sure they work as planned.

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