A woman was taken to hospital suffering shock and smoke inhalation after an e-cigarette exploded.
The explosion is thought to have occurred after an incompatible charger was used, causing the device to ignite.
Four fire engines and more than 20 firefighters rescued the woman from the ground-floor flat in Barking, east London, on Saturday afternoon. She was suffering from smoke inhalation and shock and was taken to hospital by ambulance.
The London Fire Brigade has warned about the safety of the devices and is asking users to ensure the correct charger is attached.
The blaze follows reports of an incident in Manchester where a 64-year-old woman sustained burns after apparently lighting an e-cigarette in a hospital.
Following an initial investigation, it is thought it was due to a naked flame from a cigarette lighter while using oxygen, according to Greater Manchester Police.
Charlie Pugsley, from the London Fire Brigade fire investigation team, said: "People assume e-cigarettes are much safer than ordinary cigarettes, and in most cases they are.
"The danger is that people sometimes use incorrect chargers, which runs the risk of over-charging, which can potentially have explosive results. We are calling on e-cig retailers to ensure they are selling the correct chargers for the cigarettes.
"As with all rechargeable electrical equipment, it's vitally important that people use the correct type of charger for their e-cigs to prevent fires, which can be serious and could even result in death."
The brigade said people should never leave items such as e-cigarettes on charge overnight or when they are sleeping. They also highlighted safety concerns over people lighting cigarettes when using oxygen cylinders for lung conditions.
Users should also avoid smoking or using naked flames near oxygen equipment as cylinders can explode when exposed to heat.
Smokers are increasingly turning to e-cigarettes to beat the habit, with the market for the smoking aids reaching an estimated £193 million last year, according to analyst Mintel.
Although tobacco-free, the devices do provide a hit of nicotine, leading some health experts to warn that they reinforce the behaviour of smoking, making it harder to give up in the long term.