Injured woman 'returned to blaze'.
Fire chiefs say she may have left the building - but gone back inside.
Firefighters from Denbigh and St Asaph were called to the property at Cysgod Y Graig, Denbigh at 5.13pm on Sunday.
North Wales fire and rescue service said that the occupant "appears to have attempted to re-enter the property to fight the fire, and had to be transferred to hospital for treatment for smoke inhalation."
The fire is thought to have been caused by an electrical fault in a tumble dryer.
Gwyn Jones, Community Safety Manager for Denbighshire and Conwy, urged occupants to leave blazing properties and stay outside. He said: "It is extremely important to get out of the property as quickly as possible and not return into a dangerous area for any reason.
"Smoke alarms give an early warning signal which allows everyone to evacuate the building as soon as possible. Smoke can be extremely toxic and just a few breaths can be lethal - going back in to save possessions or pets is just not worth the risk."
Fire safety officials also ask occupants to take a few steps to ensure that they use their ? Never overload the tumble dryer.
. ? Never leave it on whilst you are in bed or go out. ? Do not set the programme too long.
. ? Clean the filters regularly.
Mr Jones said these measures reduce fire risks but also advised people to get a smoke alarm.