ELECTRIC BLANKET FIRE
In a recent case, a fire occurred in a two-storey suburban house of older solid brick and tile construction. The fire started in one of the upper floor bedrooms, belonging to the middle of the three daughters of the insured owners (aged 18, 16 and 12 respectively).
We were advised that, due to illness, the occupant of the bedroom went to bed in the afternoon with the electric blanket on and awoke approximately 30 mins later to find the bed on fire near her head. She unplugged the blanket, called for help, tried to extinguish the flames with a doona which caught fire so she dropped it on the floor, then left the room and her older sister called 000.
We were unable to speak directly with the occupant of the room due to her ongoing illness. The insured advised that her daughter was a non-smoker, did not use candles, incense sticks or open flames, had no laptop or tablet in the room and had a wireless phone charger pad on the beside drawers.
However, on examination the room contained: several part-used candles (including tea lights) and boxes of incense sticks on the bookshelves; cigarette lighters, matches and cigarette papers in the bedside drawers (but no tobacco or cannabis found); many unused and part-used disposable vape pens in the drawers and in a bag on the floor; a laptop computer on the floor; no phone charger or phone.
Burn patterns showed that the fire had started on or immediately alongside the head end of the bed, where it was close to a set of drawers containing many of the above smoking-related items together with breath mints and mouth freshener.
The fragile remains of the electric blanket had largely broken up during firefighting but the controller and insertion point were found relatively intact. The controller was on a low setting and there was no evidence of electrical failure on the remaining conductors. However, internal overheating of the blanket could not be ruled out.
On the bedside drawers was a circular protection mark the size of a tea light candle, but no matching metal cup was found in the debris. It may have been moved from the area during or after firefighting.
In the debris behind and beneath the bed were large amounts of paper, confectionery wrappers and similar combustibles together with several heat-damaged but intact vape pens. There was also the badly burnt metal tube of another vape pen, with its ends and contents missing. No recognisable remains of a battery could be found.
Although failures and fires associated with rechargeable vape devices are well known, there is less published research concerning disposable devices. Anecdotal evidence from one of our team indicated that a disposable vape pen at another location had failed explosively when it was left covered in a bed with the electric blanket on.
Experiments conducted at our laboratory to simulate these circumstances involved wrapping a new vape pen loosely in fleecy blanket fabric and placing on a variable hotplate, so that the temperature could be increased in a controllable way. At a surface temperature around 50°C, the pen expelled vapour violently from the mouthpiece and as the temperature increased the mouthpiece and end cap blew away from the tube. The internal lithium-ion battery caught fire, was propelled over one metre away and initiated charring on an adjacent wooden surface.
Based on our scene and laboratory findings, there were several potential causes for this fire which could not be eliminated. These were: internal failure of the electric blanket; careless use of an open flame (tea light, match or lighter); failure of an overheated vape pen expelling a burning battery. It was therefore not possible to pursue a recovery against the electric blanket retailer.