The Air Force MAFFS teams alone dropped more than 133,000 gallons of fire retardant in the area of the Waldo Canyon fire. The bright red slurry goes through rigorous testing before being used to ensure it is safe for the environment.

The active ingredient is ammonium phosphate fertilizer, similar to the kind you'd use on your lawn. It is dyed red to show the pilots where they've already dropped and designed to stick to the trees and brush.

The slurry is not a threat to people or wildlife, and drops are coordinated to keep it hundreds of feet away from any water supplies.

"They don't want to drop in the streams, don't want to drop close to the streams,” said John Nichols of the U.S. Forest Service. “They want to stay far enough away, so that after the fire is out, the benefit stops on the hillside so it doesn't affect the drainage.”