Thousands of properties have been destroyed and 24 people have been killed in the devastating wildfires that have hit Los Angeles since Tuesday last week.
Horrific photos have emerged showing entire neighbourhoods being destroyed by the flames, families being forced to escape from their homes and firefighters working around the clock to combat the fires. There have also been numerous images of cars, roads and homes being covered by a pink powder – and many have been left wondering what it is being used for.
But what exactly is it? Here, we explain everything you need to know about this substance, including how and when it is used, and how it helps firefighters.
The eye-catching powder is a flame-retardant product called Phos-Chek, which has been used to fight fires in the US since the 1960s. It is commonly used by the California Department of Forestry and Fire Protection. It is said to be the most-used fire retardant in the world.
The product is sold by a company called Perimeter Solutions. While the exact formula of Phos-Check is not officially known publicly, it is said to contains 80 per cent water, 14 per cent fertiliser-type salts and six per cent colouring agents and corrosion inhibitors.
In a 2023 NBC Los Angeles article, Oscar Sanchez, who has worked at Perimeter Solutions for over 25 years, said the company is “always on alert, always on call 24/7” and can ship orders within hours of receiving them. Once sacks full of Phos-Check are delivered to air attack bases, the powder is mixed with water and loaded into firefighting aircraft.
Mr Sanchez added: “So all the aircraft you see dropping retardant, this is what they’re dropping. It does give us a sense of pride because it was a lot of hard work to get there.”
Phos-Check’s pink colour serves as “a visual aid for pilots and firefighters alike” as it helps them easily identify where it has been sprayed and where it hasn’t, the company said. The high visibility of the colour also allows ground crews to strategically build lines around the treated areas, which can help them protect lives and property.
After being exposed to sunlight for a few days, the colour fades to earth tones, Perimeter added. Melissa Kim, vice president of research and development at Perimeter Solutions, was quoted as saying: “We tested every colour in the rainbow, and the pink was by far the most visible. And, it’s pretty.”
She added: “If you can’t see it, then it’s essentially not effective. The purpose is they’re flying in high smoke, low visibility with winds. The pilots have to get it right the first time. This job doesn’t offer many second chances.”
Phos-Check is typically sprayed on land and vegetation surrounding wildfires to stop the flames spreading to that area. The US Forest Service said retardants “slow the rate of spread by cooling and coating fuels, depleting the fire of oxygen, and slowing the rate of fuel combustion as the retardant’s inorganic salts change how fuels burn.”
Perimeter has previously advised cleaning the powder off as soon as it is safe to do so, because if it dries for too long, removing it becomes more difficult. To clean the substance from small surfaces, warm water and mild detergent are effective. However, for larger areas Perimeter recommends using pressure washers.
In 2022, the Forest Service Employees for Environmental Ethics, which is made up of current and former employees of the US Forest Service, launched a lawsuit accusing the federal agency of violating clean water laws by dumping fire retardant from planes onto forests. The lawsuit argued the chemical kills fish and is not effective.
The following year, a US District judge agreed with the employees but said in her ruling that the Forest Service would still be allowed to use the retardant as when doing so, it asks for a permit from the US Environmental Protection Agency (EPA). This year, the Forest Service told NPR said it phased out the use of one type of Phos-Chek formula, Phos-Chek LC95, in favour of another, MVP-Fx, which they say is less toxic to wildlife.
It is not allowed to drop flame retardant on sensitive environmental areas such as waterways and where endangered species live. However, there are exceptions to his ban “when human life or public safety are threatened.”
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