Fire crews from Cookstown were dispatched to the Castle Court home on Tuesday (Jan 24) afternoon at around 3.40pm.
It is understood they had to use breathing apparatus to put the fire out with a hosereel jet.
A spokesperson for NIFRS said: "NIFRS responded to a fire at a semi-detached house at Castle Court, Cookstown.
"Firefighters wearing breathing apparatus used a hosereel jet to put out the fire.
"A 51-year-old woman received oxygen therapy for mild smoke inhalation at the scene. Sounding smoke alarm alerted occupier.
"The cause of the fire appeared accidental. Fire crews from Cookstown station attended the incident."