A man was rescued from his roof after he climbed out of a window when fire swept through his kitchen and filled his house with smoke as he slept.
When firefighters arrived at the end terrace property in Ellesmere Road North, Burngreave, at around 3.20am this morning they discovered that the man had climbed out of a window in the loft to escape the blaze.
Another man in the house was trapped in his bedroom.
Firefighters led both men to safety using ladders while others extinguished the flames downstairs.
The men were both taken to hospital suffering from the effects of inhaling smoke.
The fire is believed to have started accidentally but the exact cause is not yet known.
An investigation is underway.
Group manager Andy Hayter, of South Yorkshire Fire and Rescue, praised firefighters for their rescue efforts and control room staff who gave safety advice on the phone to keep the men safe until crews arrived.
He said it is believed that a smoke alarm alerted the men to the blaze.
"When fire crews arrived at the property the found a well developed fire in the kitchen," he said.
"It was dark, the house was smoke-logged and there was one man on the roof and another at a bedroom window.
"While firefighters were committed to the property after forcing entry, others rescued the men."
He said the fire should serve as a reminder of the importance of smoke alarms.
"One of the men said a smoke alarm sounded, so we need to confirm that. This should serve as a reminder to other landlords of their legal obligation to ensure fitted, working smoke alarms are installed in their properties. Ideally there should be one on every floor."