Firefighting aircraft are currently descending on Los Angeles to tackle some of the worst forest fires the city has ever seen. The aerial firefighters are scooping water out the ocean to tackle the blazes and dumping thousands of gallons of red firefighting liquid over the city to try and get the blazes under control. But have you ever wondered what that red firefighting liquid actually is?
It turns out that as well as dumping hundreds of gallons of water at a time out the belly of firefighting aircraft, aerial firefighters in America can also use a range of chemicals and man-made compounds to better tackle forest fires.
These chemicals have a few key advantages over simply dropping water on uncontrolled blazes. First, they help reduce the amount of fuel that a fire has, they can prevent combustion of the fuel that is available to a blaze and they make it more difficult for a fire to spread than water alone.
Here in the U.S., the most common compound to do this is called Phos-Chek, according to a blog post from fire retardant manufacturer RDR Solutions. The chemical is produced as a concentrated liquid or powder, which is diluted with water and then dropped from the belly of aerial firefighting aircraft, as RDR explains:
Phos-Chek, a fertilizer-based liquid, is one of the most commonly used fire retardants dropped from planes. It is a direct firefighting agent that contains polymers, surfactants, water, and other additives.
The polymer helps create an aqueous film on the fuel and acts as a protective barrier. The surfactants help reduce surface tension. This allows the fire retardant to penetrate the surface, while the other additives help reduce flammability.
This coating deprives the fire of oxygen and reduces its intensity. It allows firefighters on the ground to safely approach and extinguish the blaze with minimal risk of flare-ups due to wind changes or dry conditions.
The compound gets its red color from iron oxide, while the active firefighting ingredients all come with some pretty complex, and slightly scary sounding, names. Those compounds include ammonium polyphosphate, diammonium phosphate and diammonium sulfate, which can all help prevent trees and other woody materials from burning, according to the compound’s manufacturer Perimeter Solutions.
While the compound is cleared for use in America by the USDA Forest Service, there is good reason to be wary of Phos-Chek as the agency does warn against prolonged exposure to the firefighting chemical. Excessive contact with your skin can cause irritation and inhaling the compound can lead to respiratory issues, the agency explains.
Scientific studies have also found that the compound can be hazardous to wildlife, particularly fish like rainbow trout which can be harmed by Phos-Chek if it flows into rivers and streams.
If you want to find out more about the aerial firefighting tools that are at the disposal of firefighters in California, head here to see a roundup of the biggest firefighting aircraft around. We’ve also got a deep dive into the largest firefighting aircraft of them all right here.
