Why is it dangerous to use your mobile phone at gas stations?

it is dangerous to use cellphone on gasoline station because it might cause possible incident due to unsafe act. Static Electricity may trigger the sparking due to fumes if there is unsafe act and unsafe behavior. So for safety reason and as a preventive measure they strictly prohibited using cellphone at the gasoline station.

Usually fires need trigger like spark and source of energy like gas, wood, ..etc. Gas stations are full of medium of fire so any small trigger or sparks might cause a huge fire. Cell phones generate electromagnetic waves which might cause spark. so the possibility to trigger fire is high when using cell phones in gas stations as the two required elements for the fire are satisfied.

The only way that a mobile phone could generate a spark at a petrol station would be due to a defective battery, which is unlikely and could also occur in the case of the car’s own battery. While the possibility is remote, there is a low risk that an explosion could occur from the gases that are emitted by the hose and not from the fuel.

In case you do not know, there was an incident where a driver suffered burns and his car severely damaged when gasoline vapors ignited an explosion while he was talking on his mobile phone standing near the attendant who was pumping the gas. All the electronic devices in gas stations are protected with explosive containment devices, (intrinsically safe) while cell phones are not. READ YOUR HANDBOOK! Mobile phone makers Motorola, Ericsson, and Nokia, all print cautions in their user handbooks that warn against mobile phones in "gas stations, fuel storage sites, and chemical factories." Exxon has begun placing "warning stickers" at its gasoline stations. The threat mobile phones pose to gas stations and their users is primarily the result of their ability to produce sparks that can be generated by the high-powered battery inside the phone.

It is intrinsically unsafe to use mobile phone while refueling at gas station.mobile phones generate static electric that could trigger the gasoline fumes to ignite

Because of it,s strong electromagnetic waves  it cause fire .

ignition source/fire hazards

Because cellphone produce static energy and can produce ignition or initaite fire when surrounded by fumes

The only way that a mobile phone could generate a spark at a petrol station would be due to a defective battery, which is unlikely and could also occur in the case of the car’s own battery. Moreover a gas station falls under Zone 1 hence any electrical equipment inside the area must be ex proof hence as mobile is not an Ex prrof equipment so therefore there is a chance of spark generation that could approach outer environment is there, While the possibility is remote, there is a low risk that an explosion could occur from the gases that are emitted by the hose and not from the fuel.

because its wave could react with explosive atmosphere and can cause explosion

Simple answer is thi estatic spark risk.