U.S. officials are testing a new wildfire retardant after two decades of buying millions of gallons annually from one supplier. The Forest Service says tests started last summer are continuing this summer with a magnesium-chloride-based retardant from Fortress. Fortress contends its retardants are effective and better for the environment than products offered by Perimeter Solutions. That company says its ammonium-phosphate-based retardants are superior. The Forest Service used more than 50 million gallons of retardant for the first time in 2020.