Parts of Southern California are covered with pink fire retardant as firefighters try to control deadly wildfires raging in Los Angeles. But what is Phos-Chek fire retardant and is it safe?

Perimeter Solutions, the company that makes the substance, explains its hot pink hue. As crews battle fires in Los Angeles, the hot pink fire retardant they’ve dropped to stall the flames’ advance has become one of the striking visuals to come out of the disaster.

Some of the visuals coming out of Los Angeles County over the past week show a vivid pink substance coating streets, cars and plants. This is fire retardant, dropped by aerial firefighting tankers in massive plumes of red or pink to slow down fires.