Denver, CO – A Denver firefighter has been injured in a natural gas explosion on the roof of a five-story downtown building.

Fire Department spokesman Phil Champagne says the man’s injuries are not life-threatening. His name hasn’t been released.

Crews were searching for the source of a natural gas odor Tuesday night when an explosion in a heating and air conditioning unit knocked the firefighter backward eight to 10 feet.

Champagne says the explosion was only about 20 feet from the edge of the building, and it’s fortunate the firefighter wasn’t blown over the edge.