Firefighters were called to Burnley General Hospital on Monday after fire broke out in an endoscopy steriliser.
Crews wearing breathing apparatus entered the room and found a water filtration sterilising unit was well alight around 6pm.
Three carbon dioxide extinguishers were used to extinguish the blaze and limit water damage.
Crew manager Alan Ashworth said damage was confined to the unit with smoke damage to the sterilising room. Fortunately there were no patients affected by the fire as it happened at the end of the working day.
Staff were evacuated from the premises while the fire was put out.