Ethanol gives off ignitable vapour at room temperature (flash point 13°C), the vapour is explosive between 3.3% and 19% in air and runs along the floor, and the flame is nearly invisible in daylight, so keep every flame and spark away from the still, the store and the engine bay. Small fires are smothered with a lid, wet cloth or sand; a large ethanol fire can be put out with plenty of water, which mixes with the ethanol, but a bucket of water thrown on a pool of burning ethanol may only spread it.
Part of Ethanol Fuel Production
Fire safety for ethanol covers vapour limits, invisible flames, safe storage and putting out ethanol fires.
Three Facts Drive Every Rule
- Flash point 13°C. At or above that temperature, which is a normal day, enough vapour forms to ignite from a spark (parent).
- Explosive range 3.3-19% in air (parent). Below 3.3% it is too lean to burn; above 19% too rich; between, a spark makes an explosion in a confined space.
- Vapour weight 46 ÷ 29 = 1.59 times air. It sinks and travels along floors and ground to a distant flame.
Add the flame itself: ethanol burns pale, almost invisible in daylight (parent; the corpus’s alcohol-fuel guide describes it as pale blue). People have walked into burning spills they could not see.
Worked Example: How Much Spill Fills A Room To The Limit
One litre of ethanol is 0.789 kg ÷ 46.07 = 17.1 mol. As vapour at 25°C a mole takes 24.5 litres, so a litre of liquid makes 17.1 × 24.5 = 419 litres, or 0.42 m³ of vapour. A closed room 3 m × 3 m × 2.5 m holds 22.5 m³.
- 1 litre evaporated and mixed through the room: 0.42 ÷ 22.5 = 1.9%, below the 3.3% limit.
- 2 litres: 0.84 ÷ 22.5 = 3.7%, above it.
Vapour is heavy and does not mix evenly, so near the floor the concentration is higher than the average. A couple of litres spilled in a small closed room is enough to make it explosive.
What You Need
- Sealed storage: metal or glass containers, closed tight, in a cool shaded place away from buildings (parent); polyethylene loses ethanol slowly. The corpus’s storage guide is written for petroleum drums but covers the same hazard class (Storage Containers (petroleum))
- Sand or earth in buckets, a lid or heavy wet cloth, and a plentiful water supply
- Ventilation, and a grounded metal container for pouring to avoid static
- Distance: the petroleum guides keep gasoline 30 m from flame and cap a household at 5 litres (Petroleum Safety Protocols); ethanol’s flash point is higher than gasoline’s but still below room temperature, so borrow those limits as a conservative starting point, not a sourced figure for ethanol
Method: Handle And Respond
Step 1: Keep ignition away. No smoking, stoves or lamps in or near the still or store. Heat stills by electricity or steam, or with the fire outside the vapour’s reach.
Step 2: Pour carefully, outdoors where possible, with a funnel and tight containers, and wipe spills at once with a cloth that you then dry outdoors.
Step 3: Assume a fire you cannot see. If a spill may have ignited, treat air that shimmers and a warm surface as fire. Approach only with a long implement and keep your hands out of the flame zone.
Step 4: Small fire: smother with a lid, a wet cloth or sand. Large fire: use a lot of water, thrown or poured steadily, so the ethanol is diluted below the point where it burns; a little water on a burning pool spreads it (general fire practice, recalled, not sourced in the corpus). Remove people and other fuel first.
Step 5: Burns: cool with clean water for at least 10 minutes (the petroleum guide’s cooling figure) and get help.
Common Mistakes
- Using petroleum rules for water. Water on a petroleum fire floats the fuel and spreads it (Fire Prevention (petroleum vapour) is right for petroleum); ethanol mixes with water, so large amounts of water work, but a bucket does not.
- Leaving a container open. Vapour escapes and the contents absorb water.
- Refuelling a hot engine or a lit stove.
- Testing for vapour with a flame. Never. Ventilate instead; the nose is no detector for the explosive range.
You cannot see the fire
Ethanol’s flame may be invisible in daylight, its vapour is invisible always, and a small closed room needs only about 2 litres to reach the explosive limit. Never use a flame, spark or lit cigarette to check a leak.
What’s Next
- Learn next: Byproducts & Safety, for the full set of hazards
- Combine with: Sealing Joints, to keep vapour in the still