Worker exposure to toxic gas prompts safety alert

In March 2022, a worker was seriously injured after being exposed to a toxic gas following a chemical reaction in a pump shed. Initial inquiries indicate that the man was using a drum pump to deliver sodium hypochlorite inadvertently into a tank containing sulphuric acid as part of a water treatment process. As a result of the two chemicals reacting, a toxic gas was generated; it then escaped through an unsealed opening on the tank into the work area. Some chemicals used in the treatment of water supplies are incompatible with each other; that is, when brought together, they react dangerously. An example is the reaction between chlorine-based products (such as sodium hypochlorite) and acids (such as hydrochloric or sulfuric acid), which release toxic and corrosive chlorine gas when combined. Care must be taken to avoid mixing such incompatible chemicals.

Incompatible chemicals have the potential to come into contact with one another when different chemicals are dispensed or transferred using a ‘common’ container; when using contaminated or improperly labelled containers, transfer lines, or piping; or when spills or leaks of different chemicals are kept within a common spill containment system or compound.

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. Business owners and persons conducting a business or undertaking (PCBUs) are encouraged to use the hierarchy of controls to help 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, providing a step-by-step approach to eliminating or reducing risks. Business owners and PCBUs must work through the hierarchy of controls with the aim of eliminating the hazard, which is the most effective control.

The Work Health and Safety Regulation 2011 includes a number of duties for a PCBU in order to manage the risks to health and safety associated with using, handling and storing hazardous chemicals at a workplace. In addition, specific sections of the WHS Regulation require the PCBU to identify any risk of a physical or chemical reaction in relation to a hazardous chemical used, handled, generated or stored at a workplace. When considering the risks involved with the handling, use or storage of specific hazardous chemicals, an assessment of the chemical hazards, task hazards or nature of work and the work environment is required. This assessment consists of but is not limited to reviewing the container labels and Safety Data Sheets (SDS) for the hazardous chemicals and assessing the information provided on the safe storage, handling and use. The assessment also includes the implementation of additional control measures to address any identified gaps.

PCBUs must also decide whether the hazardous chemicals risk in the workplace is adequately controlled with existing control measures, as recommended in the SDS and other reliable sources, such as relevant Australian Standards, Codes of Practice, manufacturers’ guidance and related incident data and reports.

The SDS assists this assessment by providing critical information about hazardous chemicals, including health and physical hazards, safe handling and storage procedures, situations that may generate hazardous chemicals, emergency procedures, and disposal considerations. The risk of bringing two or more incompatible hazardous chemicals in contact during the transfer or dispensing process can be eliminated or minimised using a range of controls. These include ensuring containers, pipework and equipment are free from contamination, particularly from incompatible hazardous chemicals, and ensuring that transfer fittings are compatible and dedicated transfer lines are used rather than shared or common lines. Other controls include ensuring containers and pipework are correctly labelled so the contents are readily identifiable, and isolating (or segregating) incompatible hazardous chemicals from each other (this can be done by distance, barriers, or a combination of both).

Installing overflow protection on equipment and receiving vessels, and providing a spill containment system, where incompatible chemicals will not be brought into contact with each other, can also help minimise the risk of hazardous chemicals coming into contact with each other during the transfer or dispensing process. Additional control methods include the implementation of emergency shut-offs to limit the amount of hazardous chemicals released during a loss of containment. PCBUs are also advised to maintain a safe atmosphere in the storage and handling area using a ventilation system, and to design and implement planned maintenance programs for chemical handling systems that should be carried out at regular intervals, consistent with the manufacturer’s instructions or advice provided by other competent persons. Plumbed eye wash stations and safety showers can also be installed in areas where workers may be exposed, if there is a spill during transfer.

Business owners and PCBUs should only consider administrative controls when other higher order control measures are not practicable, or when they support other control measures. This can include developing policies and safe work procedures for the use, handling, storage, clean-up and disposal of hazardous chemicals, and the provision of easy-to-understand information, training and instruction to workers. Other administrative controls include obtaining the current safety data sheet (SDS) from the manufacturer, importer or supplier of the chemical and making it readily available to workers, and preparing a register of hazardous chemicals at the workplace and keeping it up-to-date and accessible to workers.

In most circumstances, personal protective equipment (PPE) such as overalls, aprons, footwear, gloves, chemical resistant glasses, face shields and respiratory protection should NOT be relied on to control risk, and should only be used when all other reasonably practicable control measures have been used and the risk has not been eliminated, or as interim protection until higher level controls are implemented. The control measures put in place should be reviewed regularly to ensure they are effective.

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