Arlington Heights firefighters were called Thursday to a minor fire at Northwest Community Hospital.
Firefighters said that around 1 p.m., maintenance workers at the hospital pulled an alarm after detecting an odor and observing a slight haze on the third floor.
Firefighters conducted a search and found that roofers, while heating roofing materials, had set some of the framing around the heating and air conditioning unit on fire.
Fire officials worked for two hours to tear through the roof with portable saws and put out the fire.
Damage is only estimated at $5,000.
The hospital activated an emergency action plan, assembling hospital staff in a board meeting room for what amounted to an impromptu drill, fire officials said.