Police were called to Stanage Walk, Grimsby, at around 11pm on January 13 after a wheelie bin was set alight and pushed against the front door of a flat.
The man inside, 67, was rescued by neighbours and taken to hospital for treatment.
He died five days after the incident, but police said a post mortem examination revealed his death was not linked to the fire.
Police have today released CCTV footage of a man they want to speak to in connection with the incident.
A boy, 13, has been bailed pending further enquiries.
Detective Chief Inspector Stewart Miller, of Humbersdide Police, said: “We are very keen to identify the person on the video to establish if they were involved in the incident or saw anything that could assist us with our enquiries.”
Anyone with information is asked to call 101, quoting crime reference number 2242442.