Assessing fire and explosion risks in possible chemical stores

Fires and explosions at worksites with hazardous chemicals have the potential to cause catastrophic damage: injuries and fatalities, destruction of property; environmental disasters.

STEP 1: Identify all fire and explosion hazards

Your first step is the identify all the chemical fire and explosion hazards at the workplace, taking the entire job site (and the neighbours) into consideration. Each hazard has the potential to impact other HAZCHEM and Dangerous Goods stores — and these must be strategically isolated and segregated to minimise the potential for danger.

Chemical Fire Hazards are substances that can burn or support a fire. They include:

Flammable liquids (eg, petrol, toluene)
Flammable gases (eg, LPG, acetylene)
Flammable aerosols (eg, spray paints, adhesives)
Combustible liquids (eg, kerosene, diesel)
Flammable solids (eg, asphalt, grease and fat)
Oxidisers (eg, hydrogen peroxide, silver nitrate)
Pyrophoric Chemicals (eg, magnesium, powdered aluminium)

Chemical explosion hazards are substances that create (or cause) an abrupt release of pressure, heat, and gas. They are activated by temperature changes, pressure, and sudden shocks. There are three types including:

Detonators (eg, TNT, nitroglycerine)
Chemicals that burn at a subsonic rate (eg, rocket fuel, gunpowder)
Compressed gases (eg, LPG, oxygen)

PLEASE NOTE: All compressed gases are potentially explosive (even seemingly inert gases like argon and helium) because any rapid release of a compressed gas creates great force. Explosions can occur when cylinders are punctured, dropped, or heated.

Once you’ve identified and inventoried the chemical fire and explosion hazards, you should review each Safety Data Sheet to help you understand how each substance contributes to either a fire or explosion. Examples include:

Flammable and combustible liquids don’t burn, it’s the vapours that burn. Research their flashpoint, which is the lowest temperature where the liquid can produce enough vapours to start burning.
Pyrophoric Chemicals ignite spontaneously when exposed to air.
Some flammable solids can ignite when exposed to water or friction. Safety Data Sheets (SDSs) will provide details of materials and situations that could trigger a fire.
Flammable gases and aerosols can ignite or explode after contact with ignition sources or if the cylinder or canister is punctured, dropped, or heated.
Oxidisers can react with other substances and create a fire (or cause an existing fire to burn with more intensity).
Explosives are activated by shocks, pressure changes, and heat.

IMPORTANT: Some hazardous chemicals can decompose if the substance is stored or handled incorrectly (eg, acetylene gas). Decomposition generates heat, and explosions. Other chemicals can ignite if they are contacted by incompatible chemicals.

STEP 2: Understand possible ignition sources

An ignition source is energy that could potentially ignite a flammable substance. Ignitions sources are categorised into three groups: flames, sparks and heat — we’ll look at each group in more detail below.

Flames — any naked flame produced by things like lit matches, cigarette lighters, welding flames, gas heaters, pilot lights.
Sparks — generated from electric motors and machinery, lightning, power-points and sockets, fluorescent lighting, welding arcs, lighters, mobile phones and electronic gadgets, thermostats, scraping metal, drilling, and grinding. Static electricity can also be produced during friction, even from clothing.
Heat — heat can be generated from hot surfaces like ovens, furnaces, radiators, flue pipes, light bulbs, machinery and engines, pumps and generators. Direct exposure to sunlight and extreme temperatures can produce enough heat to ignite various chemicals and explosives. Some chemical reactions generate significant heat.

You’ll need to locate and identify anything that has the potential to ignite flammable or combustible materials that are located on the job site; in areas adjacent to the workplace; or brought into work areas or chemical stores by contractors and delivery drivers.

Understanding and identifying ignitions sources is critical for deciding the best location for your HAZCHEM stores and will also drive your operating procedures, inductions, and staff training program.

STEP 3: Locate sources of fuel

To exist, fires require oxygen, an ignition source, and fuel. Your next step will be to locate anything that could fuel a fire or explosion. You will already have located chemicals classed as combustible or flammable (including their fumes and vapours); as well as substances in other hazard classes (eg, oxidisers). Now you’ll be identifying materials that aren’t hazardous chemicals which are potential fuel. These include:

Wood (eg, firewood, construction supplies and timber, pallets)
Paper (books, stationary, raw materials, good for resale, provisions)
Leaves and sticks (gardens, crops, forests and other vegetation)
Buildings (walls, furniture, personal effects)
Fabric (clothing, uniforms, personal effects, raw materials, stock, provisions)
Other materials (refuse, plastic containers)

When locating sources of fuel don’t forget to assess combustible materials located outside the perimeter of the job site that could potentially impact where you locate your hazardous chemical stores. Gardens, forests, and refuse from neighbouring properties can be potentially hazardous