I'm know I'm not the only one who has wondered, while filling up the car, why you're not allowed on your phone on a petrol station forecourt.
But then when you get straight back in the car and behind the wheel, you find yourself forgetting to give it a Google once you get to the end of your trip and can legally whack your phone out.
Well, there's a serious reason for not getting your phone out when you're filling up on petrol or diesel. And it could end up with an explosive conclusion if you don't obey it.
Posting last week, Shell said on its website: "It is not safe to use outside your vehicle or while driving.
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"However, it is perfectly safe to use a mobile phone inside your stationary vehicle once you're parked on the forecourt.
"Once you’ve activated the pump, please leave your phone inside the vehicle or place in your pocket or bag."
But in posting this, the company didn't explain why you can't use a phone.
Well, it's quite simple albeit very serious - but at the same time, it all needs to be taken with a pinch of salt.
Ultimately, guidance says that your device could spontaneously combust.
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The danger of using your phone at a forecourt
"The primary concern is that mobile phones, when in use, could potentially ignite flammable vapours present at the petrol station," Josh Amishav, founder and CEO of security firm Breachsense, told LADbible.
"The idea is that electronic devices, including mobile phones, can emit small electrical sparks from their battery or electronic components, especially if the device is damaged.
"These sparks could, in theory, ignite gasoline vapours that are highly flammable."
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That would obviously be very bad and potentially fatal incident at a location such as a forecourt, where flammable fuel is all around us in cars and being stored underground.
But is it a real risk?
For Amishav and others, reality is somewhat different from the theoretical risk.
He explained: "It's important to note that actual incidents of mobile phones causing fires at gas stations are extremely rare.
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"Modern mobile phones are designed to be very safe, and there's little scientific evidence to suggest that typical mobile phone use can ignite gasoline vapours.
Much of the regulation and signage are precautionary and based on general principles of minimising all potential ignition sources in environments with flammable substances."
Fuels Industry UK, the only trade association in the country for the fuel industry, adds that 'no evidence linking fires to mobile phone ignition has been found' through research carried out by the Energy Institute.
Not just explosive
Despite this, the Fuels Industry UK recommends its members actively promote messaging not to use phones on forecourts.
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The first reason is nothing to do with the technology in the device but due to the issues that phones have when it comes to being a distraction.
It says: "Using mobile phones can create a serious distraction for people dispensing fuel or crossing the forecourt due to the number of vehicles moving.
"Traffic movements will always present a risk for customers and therefore remaining vigilant and minimising distractions is central to forecourt safety.
"The distraction caused to pedestrians by mobile phones increases the risk of accidents."
On the explosive risk, it says 'mobile phones are not designed and certified for use in explosive atmospheres which exist temporarily around the pump and nozzle during refuelling'.
Those filling up their car who are seen to also be on their phone could have their access to the pump cut off by those controlling it.
Tom Earnshaw