Aircraft battling fires raging through the Los Angeles area are dropping more than water: Hundreds of thousands of gallons of hot-pink fire suppressant ahead of the flames in a desperate effort to stop them before they destroy more neighbourhoods.
The fires have killed at least 24 people, displaced thousands and destroyed more than 12,000 structures since they began last Tuesday (Jan 7). Four fires driven by strong Santa Ana winds have charred about 62 square miles, according to Cal Fire.
Fire agencies say the suppressants — most often used to fight forest fires — are an invaluable tool. But what is in them and are they safe?
Here’s what to know:
WHY ARE THEY BEING USED IN LOS ANGELES?
The fires are burning quickly through canyons and other rugged areas that are difficult for firefighters on the ground to reach, Cal Fire said.
While fire suppressants can be very effective, they do have limitations, the agency said: Strong winds can make it too dangerous to fly at the low altitudes needed for drops and can dissipate the retardant before it hits the ground.
Besides Cal Fire, multiple agencies have dropped fire retardant and water, including the US Forest Service, the Los Angeles and Ventura County fire departments, the city and the National Guard.
HOW DO THEY WORK?
Aerial fire suppressants are generally a mixture of water, ammonium phosphate — essentially fertiliser — and iron oxide, which is added to make the retardant visible, said Daniel McCurry, a civil and environmental engineering professor at the University of Southern California.
The Forest Service, which has used 13 aircraft to dump suppressants on the Los Angeles fires, says they help starve a fire of oxygen and slow the rate of burn by cooling and coating vegetation and other surfaces.
Perimeter, the company that supplies fire retardant to the Forest Service and other agencies, says the phosphate changes the way cellulose in plants decomposes and makes them non-flammable.
