Understanding how a fire can get started and burn is key to fire prevention. This is part 2 of a short blog series to help you understand fires that involve flammable liquids, and the steps you need to take to minimise the risk. In part 1 we looked at how a chemical fire can impact people, property and environment, now in part 2 we’ll be taking a closer look at the way they ignite. Use our blog series to support your fire risk assessment.
Understanding flammable liquids fires
What causes Class 3 flammable liquids to burn?
Many people don’t know that the liquid form of Class 3 Flammable Liquids does not burn, it’s actually the vapours that ignite and sustain the fire. In order to fully understand how flammable liquids create fires you need some background knowledge and you should familiarise yourself with the following:
- Flashpoint: this is the temperature range in which the chemical will burn. Your fire risk assessment should consider if the chemicals you hold onsite are used or stored at temperatures inside the flashpoint range. For many common flammable liquids (eg, petrol), the flashpoint is normal room temperature.
- Flashback: flammable liquids emit vapours that are heavier than air. When a chemical container is opened (or if chemicals spill) vapours can travel long distances and remain flammable. Your risk assessment should consider work operations (or unplanned incidents) that could produce a flammable vapour trail.
- Auto-ignition: most flammable liquids have an auto-ignition temperature. Chemicals used or stored within their auto-ignition temperature range don’t need an ignition source to ignite. Your risk assessment should consider if the chemicals onsite could reach their auto-ignition temperature (eg, could an unventilated cabinet stored outside in the sun reach the auto-ignition temperatures).
- Explosive range: flammable liquids also have an explosive range. When vapour concentrations and temperatures are within a certain range, if ignited the flammable liquids will explode. Your risk assessment should assess the possibility and likelihood of chemicals reaching their explosive range.
What potential ignition sources are present at your job site?
Once you have an understanding of the conditions that could produce a flammable liquids fire, you should then identify possible ignition sources. Under Section 355 of the WHS Regulations you have a responsibility to ensure that ignition sources are not brought into work or storage areas that contain flammable liquids.
“A source of energy sufficient to ignite a flammable or explosive atmosphere. Examples of ignition sources include naked flames, hot surfaces, exposed incandescent material, electrical wiring arcs, mechanical or static sparks, hot particles, electrical discharge, and electrical or mechanical equipment not suitable for use in hazardous locations.”
Definition: Ignition Source
AS1940:2017 - The storage and handling of flammable and combustible liquids
You need to apply this definition to the equipment, machinery and processes everywhere at the workplace that flammable liquids are carried. Let’s look at each of them individually and consider if they could be found at your job site.
- Naked flames. Matches, lighters, bunson burners, pilot lights.
- Hot surfaces. Cigarettes, hotplates, welders or flame cutting equipment, machinery that has overheated or malfunctioned, friction from loose belts and worn bearings.
- Exposed incandescent materials. Incandescent light bulbs, halogen lights.
- Electrical wiring arcs. Loose wiring and faulty electrical connections.
- Mechanical or static sparks. Grinders, electric drills, spark ignition systems, hand tools.
- Hot particles. Welding slag and hot metals.
- Electrical discharge. Power points, light switches, static electricity.
- Electrical or mechanical equipment not suitable for use in hazardous locations. Non-flameproof electrical cables, cords, switches, lights, connectors or fittings.
IMPORTANT: with so many acts of terror and violence in the world in recent times, you must not rule out arson and other deliberate acts as an ignition source.
Preventing flammable liquids from igniting
We always recommend carrying out a risk assessment if your workplace carries Class 3 Flammable Liquids, but even without one you could implement the following measures:
- Storing flammable liquids in a Class 3 Flammable Liquids cabinet.
- Locating the cabinet away from electric tools, power sockets, furnaces, heaters, electronics that can discharge static electricity, machinery that could create friction, sparks, or heat.
- Banning smoking and personal electronics within 5 metres of flammable liquids stores.
- Restricting workplace activities (eg, welding, vehicular repairs, deliveries, forklift loading) near safety cabinets and chemical stores.
- Keeping the lids on chemical containers when not in use.
- Controlling the use, storage and disposal of oily rags.
- Cleaning up spilled chemicals immediately and disposing of flammable waste carefully.
- Ensuring workers and maintenance contractors use only tested electrical tools and don’t overload circuits.
- Replacing electric and gas heaters with central heating.
- Carry out preventative maintenance on plant and machinery. Eg, clearing dust and refuse from vents on machinery — clogged vents can cause the machines to overheat.
If you’re serious about preventing the flammable liquids at your job site from igniting or contributing to a workplace fire, why not download free eBook Essential Considerations When Storing Flammable Liquids Indoors. It has everything you need to select and install a fully compliant flammable liquids cabinet at your job site. Download and read it now by clicking on image below:
Read the whole series
- Things you need to know about fires that involve flammable liquids (Part 1) Workplace and Community Impacts.
- Things you need to know about fires that involve flammable liquids (Part 2) Ignition Sources.
- Things you need to know about fires that involve flammable liquids (Part 3) Fire combustion and escalation.