Humberside Fire and Rescue Service said firefighters and paramedics had been called to an address in Hilderthorpe Road shortly before 7.50am this morning.
They said the man had suffered burns due to a reaction between the spare battery for a vaping machine and a metal chain in his trouser pocket.
Firefighters made a safety inspection before leaving the man in the care of paramedics.
It prompted the service to later issue a safety warning to members of the public.
A spokesman said: "Please only use the charger sold with your vaping device, otherwise lithium ion batteries can overheat and cause a fire.
"Even once charged, other metal objects in your pocket such as coins or keys can short circuit the battery causing a localised explosion."