Arsonists use packets of crisps to help them start fires — with their fat and calories proving a potent accelerant that can set a car seat ablaze in minutes.
Bags of crisps have an advantage to criminals in being far more innocuous than a can of petrol and burn in a way that leaves little evidence behind.
Fire investigators were alerted to this method of fire-starting by colleagues in the prison service, who heard about the technique from inmates.
The practice has reportedly been in use for at least ten years — and is well known amongst prison populations.
To investigate how potent a pack of crisps can be as a fire accelerant, forensic scientists Emily Duffin and Linda Brownlow of the University of Greenwich, London, experimented by setting light to 10 different types of crisp.
The researchers measured how easily the crisps could be set alight, for how long they burned and long they stayed hot after the flames had died down.
Each bag’s ingredients, crisp shape, packaging type and calorific value were noted.
In the second stage of the research, the duo explored how quickly a lit bag of crisps could set fire to a car seat — a good substitute for home furnishings like sofas and which could safely be set alight outside.
The researchers conducted these larger-scale tests in the facilities of the Fire and Rescue Service Headquarters in Maidstone, Kent.
Packets of crisp prove to be excellent accelerants, they found — with each individual crisp burning for an average of around 76 seconds.
‘Crisps encourage fire — they feed it — because they are hugely calorific and fatty,’ explained Ms Brownlow.
‘As the video shows, a packet of crisps — either the potato ones or the puffy, maize or corn-based ones — can set a car seat on fire within 200 seconds.’
On average, the fire from the makeshift accelerant packets spread to the car seats in 100 seconds.
This, she notes, is ‘plenty of time for someone to get away.’
‘In terms of calories, there was little difference in everything tested. They all lit and burned quickly and strongly enough to set the seat on fire,’ added Ms Duffin.
The firefighters at the test expected the crisps to go out before they had a chance to set the seat on fire — they were amazed.’
‘When forensics teams go to investigate arson they’re looking for an accelerant, such as petrol,’ said Ms Brownlow, who is the former head of Head of Crime Scene Training for the Metropolitan Police.
‘Also, someone looking to start a fire who is carrying a can of petrol stands out. No one’s going to look twice at someone with a bag of crisps, and the evidence destroys itself.’
‘This is especially helpful if someone is trying to make a deliberate fire look accidental. Criminals have presumably worked this out and told each other.’
The researchers noted that there was no statistically significant difference in how different types of crisp burn.
With their initial study complete, the team will now be investigating whether a bag of crisps could stay alight long enough to start a fire were it thrown through a letterbox.
‘That sort of malicious damage is more common with “amateur” arsonists, rather than covering up a crime,’ said Ms Brownlow.
‘I’m not convinced a thrown pack would stay lit for long enough but this is why we test things, you never know.’
‘We’ll need to build a rig, a kind of mock hallway, with a door and letterbox and various floor types so we can compare burn patterns on the back of the door.’
The full findings of the study were presented at the International Conference on Fire Safety Science and Technology, which was held in London from September 25-26.
