An elderly man was among three people taken to hospital after the fire in Meeds Road, Burgess Hill, yesterday (Monday).
He is understood to be aged 93 and the occupant of the semi-detached bungalow where the fire started before spreading to the adjoining property.
Also taken to hospital was a firefighter who was injured when a piece of ceiling collapsed on to his head and a neighbour who alerted the man when she saw smoke coming out of the roof of his home.
The firefighter was sent as a precaution and was not seriously hurt, according to West Sussex Fire and Rescue Service.
The neighbour suffered from the effects of smoke inhalation. The cause of the fire is believed to have been accidental.
Cllr Anne Jones, who witnessed the drama, said: “We were all very concerned for the people involved.
“All the emergency services worked together as a team, not only coping with the fire but looking after the people involved as well.”
See more on this story in Thursday’s Mid Sussex Times.