An off-duty firefighter in Didcot raised the alarm after a fire broke out in a second-floor flat.
The officer was at Great Western Park when he heard the Greenwood Way flat’s smoke alarm going off at 10.20pm on Monday last week.
After calling for back-up, crews from Wallingford, Abingdon and Oxford attended the scene.
When they got inside they discovered the flat’s sprinkler system had already suppressed the fire.
The occupant of the flat, which is owned by Oxford City Council, has been rehomed until repair work is carried out.
Station manager Paul Webster said without the sprinklers the fire “would have continued to grow”.
He added: “Thankfully there was no one in the property at the time of the fire but smoke alarms alerted the rest of the residents in the block of flats.
“There is no doubt that if the flat had not got a domestic sprinkler system, then the whole flat would have become involved in fire so the level of damage would have been far worse.”