A man aged in his 40s was saved by firefighters from a 12th floor apartment in Callow Drive, Heeley, at 12.50am on Saturday after a blaze was sparked in the kitchen.
He was treated for smoke inhalation as four fire crews from Central, Birley and Lowedges stations battled the flames.
A spokeswoman for South Yorkshire Fire and Rescue said the blaze was caused by unattended cooking and firefighters were also called to a second similar incident later on Saturday.
A pan left on the hob caused smoke to fill a property in Firshill Croft, Pitsmoor, at 2.15pm. A crew from Elm Lane Fire Station attended but the blaze was out on arrival. No injuries were reported.
The fire service is now urging people to never take the risk of leaving cooking unattended.
A spokeswoman said: "Take extra care in the kitchen and never leave cooking unattended. Never, ever use a chip pan or any other pan filled with hot oil."
Elsewhere, an electrical fault caused a blaze in the loft of a home in Highwoods Road, Mexborough, at 2.15pm on Saturday. Crews from Dearne and Edlington stations spent 20 minutes putting the fire out. No-one was injured.
A fence caught fire in Swan Street, Bentley, at 8.45pm last night. The property owner was burning waste in the garden when flames spread to the fence. A crew from Adwick Fire Station put the blaze out.