David Thomson, 62, was found dead in the living room of a property in Wallasey, Merseyside.
Investigators from Merseyside Fire and Rescue Service (MFRS) found that an e-cigarette that had been charging in Thomson's bedroom exploded, caught fire and ignited the oxygen tube of an oxygen concentrator, which may have been in use by him.
There was a small amount of smoke damage to the property, though the fire in the bedroom had been extinguished by the time firefighters arrived.
The exact cause of Thomson's death has not been established.
It was the ninth fire involving e-cigarettes on Merseyside alone since the turn of the year, MFRS said. It has launched a campaign to give help and advice on smoke alarms and the use of the devices and their chargers.
MFRS area manager Myles Platt said: "The investigation into the cause of this fire is continuing but at this stage it is thought that the charging device being used at the time may not have been the one supplied with the e-cigarette.
"We urge people to always use electrical equipment in accordance with the manufacturer's instructions and guidance, always ensure that no electrical items are left charging overnight or left unattended for a long period when being charged and do not mix parts from different e-cigarettes."
The government's chief fire and rescue adviser, Peter Holland, said fire deaths had fallen in recent years but people must still follow safety advice.
A spokesman for Merseyside Police said Mr Thomson's death was not being treated as suspicions and had been referred to the coroner.
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