Fire retardant used to smother fires—also called slurry—is a mixture of water, fertilizer and chemicals. It’s dropped from planes and is usually a bright red color, so air crews can track what they’ve used. But this powerful way to help slow down fires also comes with a big price tag and some environmental concerns.

Originally released by Inside Science, 2018. Streaming video file encoded with permission for digital streaming by Infobase on August 15, 2018.

The Science Behind Slurry (3:17);.