FIREFIGHTERS were called to Maltby Close, Moorside, at 12.40am, today, to tackle a fire which had broken out in the bedroom of the upstairs flat.
Three people - two men aged 47 and 26 and a woman aged 29 - managed to escape the property after hearing the smoke alarm sound.
They also alerted the family living directly downstairs to the blaze.
All three suffered from smoke inhalation and were treated by paramedics.
Firefighters took an hour and 20 minutes to tackle the flames which could be seen coming from the window as crews arrived.
The bedroom was destroyed in the fire.
Crew Manager Warren Mulvaney from North Moor and Farringdon station said: “They were very lucky as they managed to escape without any serious injury.
“If they hadn’t been alerted by the smoke alarm, the consequences could have been a lot more serious.
“At the end of the day we have three people who are alive who may not have been if they didn’t have a working smoke alarm.
“We can’t stress enough just how important it is for people not to just have a smoke alarm fitted, but to also test it on a regular basis.”
The cause of the fire is unknown and a fire investigation has been launched.