Fuel vapour, not liquid, is what explodes, so work outdoors and upwind, keep every flame, spark, hot surface and running engine away, and stand the container on the ground with the nozzle touching it to discharge static. Never use a flame to check for vapour, treat any smell of fuel as proof that vapour is present, and put out a fuel fire with sand, soil or a Class B extinguisher rather than water.
Part of Fuel Siphoning & Storage
Fuel vapour, not the liquid, is what explodes, and every other fuel procedure assumes the ignition, ventilation and spill rules set out here.
Vapour Travels Along The Ground To Whatever Ignites It
A cup of liquid gasoline burns fiercely but in a controlled way in open air; in an enclosed space the same cup produces enough vapour to fill the space with an explosive mixture (parent article). Gasoline vapour is heavier than air, so it flows downhill and collects in pits, trenches, basements, drains and vehicle footwells, and it can travel a surprising distance from the spill to a flame. Gasoline is explosive across a wide range of vapour-to-air mixtures, which is why a small spill in a closed room is so dangerous. Diesel, heating oil and kerosene give off far less vapour, but they burn, and a hot surface or mist can ignite them.
What You Need
- An open-air work area, with a way out upwind.
- Sand or dry soil in buckets, and a Class B extinguisher if one is available (parent article).
- Eye protection, gloves and clothes of natural fibre where possible.
- A second person to watch for ignition sources and raise the alarm.
Method: Control The Ignition Sources, Then The Vapour, Then The Spill
Step 1: Clear ignition sources. Remove cigarettes, campfires, stoves, pilot lights, running engines, generators and equipment that arcs or switches, from the work area and from downwind of it.
Step 2: Work in the open. Choose an open, level spot, and avoid pits and hollows. Avoid enclosed rooms. In a shed, open doors at both ends and keep the work at the entrance.
Step 3: Discharge static before opening. Touch a bare metal part of the vehicle before opening the fuel cap (parent article), and keep the container on bare ground with the nozzle or hose touching it. If you sit down in a vehicle during the job, touch bare metal again before you go back to the nozzle, because static can build up on you as you move.
Step 4: Use the nose, not a flame. Treat any fuel smell as proof of vapour, and never lower a flame or anything glowing into a tank, container or pit to test for it.
Step 5: Stay out of confined spaces. Do not climb into a tank, pit or sump. Vapour displaces air as well as being flammable.
Step 6: Control spills at once. Cover a spill with sand or soil to absorb it, shovel the absorbed fuel outdoors into a metal container, and keep ignition sources away. The parent article’s rule is to ignite nothing nearby until the spill has evaporated: 15-30 minutes in warm weather, longer in cold weather. In a low or closed space it can be far longer. While you can smell fuel, vapour is still there.
Step 7: Refuel engines cold and stopped. Let a hot engine or generator cool before adding fuel, and stop a running one first.
Step 8: If fuel ignites, smother it with sand, soil or a Class B extinguisher. Water spreads burning gasoline (parent article). Pull people back before fighting a fire larger than a bucket of sand can handle. If clothing ignites, stop, drop and roll; for the injury see Severity Assessment.
Common Mistakes
- Fighting a fuel fire with water. It floats the fuel and spreads the fire.
- Assuming a spill is safe once it looks dry. Vapour lingers in low spots after the liquid has gone.
- Smoking “downwind” of the work. Vapour does not always follow the wind.
- Fuelling a hot generator. Spilled fuel meets a hot surface.
- Testing with a flame. The vapour is what the flame ignites.
Safety
Vapour in a confined space can explode and suffocate
A mixture of gasoline vapour and air in a closed or low space can explode from a spark, a hot surface or a static discharge, and the same space can lack breathable air. Do not enter tanks, pits or sumps. Never use a flame, match or candle to detect vapour or to look into a container. Never siphon into a plastic container sitting on a car seat or carpet, and never start a siphon by mouth, because gasoline in the lungs causes chemical pneumonitis. If fuel gets on skin, wash it off at once with soap and water; if clothing is soaked, remove it before going near any flame.
What’s Next
- Learn next: Storage & Safety — building these rules into the fuel store
- Combine with: Siphoning Techniques — doing the transfer without breathing the fuel