There is a good chance that your workplace carries some form of combustible liquids. As a necessary fuel that powers all types of industries, combustible liquids are carried at most workplaces across the country. Some commonly used substances that are identified as combustible include motor oils, linseed oil and ethylene glycol. However, don't be fooled into thinking that these substances are a low-risk chemical. While they may not pose the level of fire and explosion risk that flammable liquids do, these substances must still be carefully managed to ensure ignition does not occur.
To get a better understanding of the dangers that these substances pose, we’ll look at the process of combustion and offering the definition and hazards associated with combustible liquids.
What is Combustion?
Combustion is a chemical reaction that occurs between a fuel and an oxidising agent, such as oxygen. The process of combustion releases energy in the form of heat and light.
As a type of exothermic reaction, combustion releases more energy than it absorbs.
While combustion is a necessary process for energy, cooking, transportation and other essential tasks, the combustion of a fuel and other workplace chemicals can create hazards is not handled and managed in a safe way.
How are Combustible Liquids Classified?
Now that we understand the meaning of 'combustion', let's apply this to combustible liquids in your workplace.
Combustible liquid chemicals are substances with the potential to catch fire and burn when exposed to an ignition source. They are classified as ‘combustible’ due to their flash point.
A flash point is the lowest possible temperature that allows for sufficient flammable vapours to be released from a liquid, so that ignition can occur.
Combustible liquids, such as engine oil, are classed as such due to their flash point.
As combustible liquids have a relatively low flash point, they have the potential to vaporise and create an ignitable mixture.
Hazard Class of Combustible Liquids
To understand how to control combustible liquids in the workplace, you need to first determine the hazard – or dangerous goods – class of your substance.
In Australia, combustible liquids are recognised as Class 3 dangerous goods.
These substances are further divided into categories based on their ability to combust. This division is determined by the flash point of the substance.
Hazard classifications
Combustible liquids are liquids that have a flash point and fire point that is below its boiling point. Combustible liquids are divided into two classes:
Class C1 Combustible:
A C1 combustible liquid has a closed cup flash point of greater than 60 °C, but less than 93 °C.
Class C2 Combustible:
A C2 combustible liquid has:
- A flash point of greater than 93 °C.
- Been excluded from being classified as a flammable liquid by any of the criteria for sustaining combustion.
IMPORTANT: Combustible liquids have a higher flash point than flammable liquids and therefore they are recognised as less volatile substances. Learn more about flammable liquid flash points by reading our popular blog.
Flash Point of Combustible Substances
Flammable liquids and combustible liquids are both liquids that can burn. Combustible liquids have similar properties to flammable liquids, however, the difference lies in their flash point range.
The lowest temperature at which a flammable or combustible substance produces sufficient vapours to cause a fire or explosion is known as the flash point. Different substances have different flash points, which can vary widely depending on their chemical composition and physical properties. Substances with lower flash points are generally considered more hazardous because they have a higher tendency to release flammable vapours at lower temperatures (ie. regular workplace temperatures).
There have been incidents of combustible liquids causing fires which have devestated businesses and surrounding communities.
The flash point is an important property used to classify and handle both flammable and combustible liquids. Understanding the flash point of the substance helps determine the potential fire hazard and the appropriate safety precautions required when storing, transporting and using these chemicals.
While it’s true that the flash point of combustible liquids is higher than those of flammable liquids, these substances must still be kept away from ignition sources, such as naked flames, to prevent incidents of fire or explosion.
IMPORTANT: If you have combustible liquids in your workplace, choose a compliant Class 3 storage cabinet or Class 3 outdoor storage container to safely house your liquids and minimise risk.
Fire & Explosion
Then two key risks associated with combustible liquid use in the workplace are incidents of fire and explosion.
Combustible liquids can easily ignite if they reach their flash point temperature and there are sufficient flammable vapours produced. If the workplace has insufficient controls or ventilation – and there is an ignition source present – the combustible liquids can create a fire or explosion.
Therefore, we suggest:
- Keeping combustible liquids in an environment below their flash point
- Ensuring all heat sources are segregated from combustible liquids
- Providing a well-ventilated environment for storage and handling
- Placarding combustible liquid stores with signage including COMBUSTIBLE LIQUIDS written in 50mm lettering, along with a NO IGNITION SOURCE, NO SMOKING WITHIN 3m sign
- Ensuring spill kits are available and a team is trained in effective spill response
- Decanting of combustible liquids is done to minimise the likelihood of ignition and vapour emissions
- Storage must contain any leaks or spills, with sumps regularly checked and cleaned out
- Handling areas must be free from ignition sources
- Segregation of incompatible substances must be maintained
- The correct PPE must be provided and maintained for health and safety
- Implementing chemical hazard training to increase staff safety
- Ensuring safety data sheets are available for staff, with the current version ideally stored in a dedicated SDS document holder attached to the storage cabinet or outdoor chemical store
IMPORTANT: For detailed advice on the storage of combustible liquids, read our post How Do You Store Combustible Liquids?
Identifying Hazards and Controls with Safety Data Sheets
To mitigate fire and explosion risks associated with your combustible liquids, it's vital that you have the right information about how your substances should be identified, handled and stored. The correct handling and storage of combustible liquids will assist in the control of flammable vapours, as well as the prevention of leaks and spills.
Combustible liquids require dedicated storage to minimise likelihood of fire or explosion. Refer to your substance's SDS for further details on storage requirements.
The first place to look when gaining knowledge about your combustible liquids is the current safety data sheet for each chemical that you're carrying.
Your safety data sheet offers a comprehensive range of information to help you work safely with your combustible liquids, such as the flash point of your chemical.
Your safety data sheet will include a wide range of vital safety information, including:
- Hazard identification
- First aid measures
- Firefighting measures
- Spill containment information
- Directions on handling & storage
- PPE and exposure control recommendations
- Physical & chemical properties of substance
- Dangerous goods class of product
By applying the requirements of your safety data sheets, along with the Australian Standard 1940, you can ensure that you’re doing everything possible to create a safe working environment that allows for the compliant storage and handling of combustible liquids.
REMEMBER: To determine the class of your chemical products, see Section 14: Transport Information for details on the hazard class or classes of your onsite substances.
Working with Class 3 Combustible Liquids
When the flash point of the combustible liquid is reached, the flammable vapours produced are sufficient to cause a fire — if the vapours meet an ignition source. The flammable vapours can travel throughout your workplace and accumulate in low lying areas. These vapours can also harm workers through skin, eye and respiratory irritation. To reduce the risk associated with combustible liquids, we highly recommend investing in Class 3 safety cabinets or Class 3 outdoor storage containers that can mitigate the risk of spills, fire and explosion associated with combustible liquids. If you require the transfer of combustible liquids, such as oil, an all-in-one dispensing and storage solution, such as our lubrication station, is a safe and convenient option.
To find out more about dangerous goods safety, why not access our free eBook? Our guide will explain how to control dangerous goods and hazardous chemicals, with practical advice and expert tips to help you maintain compliance and safety. 
