An e-mail about the risk of static fires at petrol stations has been circulating for quite some time.

The e-mail, which claims to be issued by Shell Oil, maintains that using mobile phones while filling up the petrol tank causes the fires.

However, Shell Malaysia released an official press statement denying having issued the following warning:

“There is a sticker to this effect at every pump that also advises customers to switch off the car engine and to refrain from smoking for similar reasons.

“We understand that there is an e-mail circulating, a purportedly official Shell communication, which describes various incidents that are supposed to have occurred as a result of mobile phones ringing while at a petrol station.

“Please be advised that the e-mail in question does NOT originate from Shell Malaysia and we are unable to confirm any of the incidents quoted.”

However, according to a report issued by the Australian Transport Safety Bureau, although fires caused by static electricity at petrol stations are uncommon, “there have been a small number of cases that have demonstrated that static-ignited fires at petrol stations do occur”.

“The open air environment of petrol stations is not conducive to the conditions required for static to ignite the fuel vapours,” it said.

The study quotes investigations conducted by the oil company BP who said the fires have been caused by discharge of static from the motorist’s body.

The shock caused by static electricity is due to the friction between the person’s body and the car seat and causes both the person and vehicle to be electrically charged.

The static electricity is discharged when the person touches the metal car door on exiting. “However, if the first point of contact happens to be the metal fill point of the dispenser nozzle, the spark may ignite the surrounding fuel vapours and cause a brief flash fire,” said the report.

It added that the risk of static igniting a fire is higher when the motorist re-enters the vehicle during refueling.

As the motorist slides over the seat, the interaction between their clothing and the seat fabric can generate a fresh charge of static electricity. If the motorist returns to the fuel dispenser without having touched any metal, the electricity may discharge from their body on contact with the nozzle.

According to an article on the BBC website, “the commonly-held belief that turning on a mobile phone in a petrol station can cause an explosion could be a myth”.

A lit cigarette was not hot enough to ignite petrol at a filling station, let alone the low voltage of a mobile phone, the article said.

The manufacturers’ warnings not to use mobiles at petrol stations because of the risk of fire gave the idea further credence.