Ignition sources and static electricity

Lesson 3 showed that fuel vapor is always present around dispensers and fill ports, at least in small amounts, and that it collects near the ground. Keeping it from igniting therefore depends on controlling ignition sources. Some are obvious, such as a lit cigarette or a welding torch. Others are easy to miss, such as the static charge that builds up on a person sliding across a car seat. This lesson goes through the ignition sources at a fuel station, explains static electricity in plain terms, looks at what the evidence says about mobile phones, and sets out the rules that control ignition on the forecourt.

The ignition sources at a station

• Smoking and open flames: cigarettes, lighters, matches, candles and barbecues. Smoking is banned near dispensers and fill ports by fire codes, and signs must say so.
• Vehicles: hot exhausts and catalytic converters, sparks from electrical faults, and running engines. Fire codes require engines to be stopped during fueling.
• Static electricity: discharges from people, containers and vehicles (below).
• Electrical equipment: lighting, signs, dispensers, card readers, vending machines and power tools. Equipment near dispensers must be designed for hazardous locations, which is why ordinary extension cords, space heaters and power tools must not be used on the forecourt.
• Hot work: welding, cutting and grinding during maintenance; never without a permit and controls (HSE-333).
• Lightning, in storms.
• Friction and impact: dragging metal, a vehicle scraping the ground, or a dispenser knocked over.

What static electricity is

Static electricity is an electric charge that builds up when two materials touch and separate. Walking across a carpet in winter and then getting a shock from a door handle is the everyday example. At a fuel station, charge builds up in three main ways. A person sliding across a car seat, especially in dry winter air and in clothing made of synthetic fabrics, picks up a charge on their body. Fuel flowing through a hose or splashing into a container picks up charge from the friction of the flow. And a container sitting on an insulating surface, such as a plastic truck bed liner or a carpeted trunk, cannot let charge drain away.

A static charge does nothing until it finds a path to ground. Then it jumps as a spark, which can carry enough energy to ignite gasoline vapor, because the vapor needs only a tiny spark to ignite when it is in its flammable range. The spark happens at the moment of contact, typically when a charged person touches the metal nozzle at the fill neck, exactly where the vapor is richest.

What the evidence shows

The Petroleum Equipment Institute, an industry association in the United States, has collected reports of refueling fires for many years. Its records show that static is a real cause of fires at the pump, and that many of the reported incidents involved a person who got back into the vehicle while fueling and then returned to the nozzle. More of these fires happen in cold, dry weather, when static builds up more easily. The pattern is consistent: the fire starts at the fill neck the moment the charged person touches the nozzle, and the person often panics and pulls the burning nozzle out, spreading the fire.

Mobile phones are a different story. Caution stickers on dispensers have long told customers not to use phones while fueling, and many people believe phones ignite vapor. Investigations by the fuel equipment industry have not found a confirmed case of a mobile phone igniting vapor at a fuel station; the reported incidents blamed on phones turned out, on investigation, to be static. Phones remain a distraction, and distracted customers overfill tanks and walk away with the nozzle in the car, so keeping phones away during fueling is still sensible. But the real ignition risk to talk about with customers is static, not phones.

What to do if a fire starts at the fill neck

Customers and workers need to know one simple rule: if a fire starts at the fill neck during fueling, leave the nozzle in the vehicle and back away. Pulling the nozzle out sprays burning fuel over the person and the ground. With the nozzle left in place, the fire at the fill neck usually stays small, and the cashier can stop the pump with the emergency shut-off (Lesson 7). The fire can then be put out with an extinguisher by someone trained, or left for the fire department.

Preventing static fires

• Stay outside the vehicle while fueling. This is the single most effective step and is printed on dispenser signs.
• If you must get back in, touch a metal part of the vehicle body, away from the fill neck, with your bare hand before touching the nozzle again. This discharges your body safely.
• Never use the nozzle's hold-open latch, where provided, and then get back into the vehicle.
• Fill portable containers only on the ground, with the nozzle kept in contact with the container (Lesson 6), never in a truck bed, trunk or on a car seat.
• Do not let children operate the pump.

For workers, the same rules apply when fueling a company vehicle or helping a customer, and staff should wear footwear and clothing that do not build up excessive charge. Most ordinary work boots and cotton clothing are fine; layers of synthetic fleece in dry winter air build up the most charge.

Static risk checklist

Marco uses a short checklist when training cashiers, to help them recognize a customer who is at higher risk of a static fire. The program below scores the factors present in a few situations. The factors and weights are an illustrative teaching tool, not a validated risk model; any situation with a container in a vehicle, or a customer returning to the nozzle after sitting in the car, deserves attention whatever the score.

# Score static-ignition risk factors for fuelling situations (illustrative weights).
factors = {
    "re-entered vehicle during fuelling": 4,
    "container filled in truck bed or trunk": 5,
    "cold, dry weather": 2,
    "synthetic fleece clothing": 1,
    "nozzle hold-open latch used": 1,
    "touched car body before nozzle": -3,
}
situations = {
    "winter, re-entered car, touched body first": ["re-entered vehicle during fuelling", "cold, dry weather", "touched car body before nozzle"],
    "winter, re-entered car, fleece, latch on": ["re-entered vehicle during fuelling", "cold, dry weather", "synthetic fleece clothing", "nozzle hold-open latch used"],
    "summer, stayed outside": [],
    "jerry can in pickup bed": ["container filled in truck bed or trunk"],
}
for name, present in situations.items():
    score = max(0, sum(factors[f] for f in present))
    level = "HIGH - intervene" if score >= 5 else ("watch" if score >= 3 else "low")
    print(f"{name:44} score {score:2}  {level}")

winter, re-entered car, touched body first   score  3  watch
winter, re-entered car, fleece, latch on     score  8  HIGH - intervene
summer, stayed outside                       score  0  low
jerry can in pickup bed                      score  5  HIGH - intervene

The checklist puts the jerry can in the pickup bed and the winter customer who got back into the car with a fleece on and the latch engaged in the high group. The customer who got back in but touched the car body first scores lower, because touching the body discharges the static. The value of a checklist like this is that it trains the eye: once cashiers know what to look for, they notice the person climbing back into their car with the pump running.

Electrical equipment and hazardous locations

Around dispensers, fill ports and vents, fire and electrical codes define hazardous (classified) locations where flammable vapor may be present. Electrical equipment in these areas, such as dispenser electronics and lighting, must be specially designed so that it cannot ignite vapor. For workers, this has practical consequences. Do not bring ordinary electrical equipment into the forecourt: no extension cords run to the pumps for a space heater or a radio, no power tools for a quick repair, no portable fans or lights plugged in near the dispensers. Report damaged electrical equipment on the forecourt, such as a broken light fixture or an exposed wire at a dispenser, and stop the affected dispenser until it is repaired.

Lightning and storms

Lightning can ignite vapor at vents and fill ports and can damage dispenser electronics. Most stations do not close for thunderstorms, but deliveries should stop while lightning is close, because the fill ports are open and the tanker driver is standing at them, and staff should not be out on the forecourt doing tasks that can wait. A common rule of thumb is to wait until 30 minutes after the last thunder before resuming outdoor work and deliveries. Severe weather such as high winds and hail also brings its own forecourt hazards: flying debris, damaged canopy panels and power failures, after which the pumps and the tank monitoring system must be checked before fueling restarts. Lesson 11 covers severe weather as part of emergency planning.

Smoking, flames and vehicles

Fire codes prohibit smoking and open flames near dispensers and require signs saying so, and require engines to be stopped during fueling. Electric vaping devices are not open flames but contain lithium-ion batteries and heating elements, and many stations apply the no-smoking rule to them too. The cashier enforces these rules with the tools available: refusing to authorize the pump until the engine is off or the cigarette is out, using the intercom, or stopping the pump.

For supervisors: make enforcement easy

Cashiers find it hard to confront customers, especially alone at night. Make it easier. Keep the signs clear and visible at every pump. Give cashiers a short script for the intercom, such as: Sir, please put the cigarette out before fueling, the pump will not start until you do. Make it clear that stopping a pump for a safety reason is always supported, even if the customer complains. And log each incident; if the same customers keep breaking the rules, the manager can deal with them.