For both air and ground?

Yes, for 60 years, it has been proven as the best retardant to render vegetation nonflammable. At least 10 different chemicals have been tested for cost efficacy and environmental impact. The main criticism against Perimeter is that it kills fish. If you dump a large amount of ammonium into an active body of water with fish, it will kill them. But why would you dump a large amount of fire retardant into an active body of water? That would be a mistake. People focus on the one in a thousand cases where the pilot makes a mistake, pushes the button too early, gets nervous, or gets scared in the smoke and drops a bunch of it in water. Intelligent environmentalists say, okay, it will happen once in a while. There will be some dead fish occasionally, but there won't be dead people or burned communities. This is the best retardant, and it's effective.