Is Phos-Chek Fire Retardant Safe? Experts Weigh In as Wildfires Burn in U.S.

As wildfires burn across Arizona and Minnesota, and with fire season ramping up nationwide, questions are once again being raised about the bright red fire retardant seen falling from planes—Phos-Chek.

Manufactured by Perimeter Solutions, Phos-Chek is a staple in wildfire suppression, coating homes, hillsides, and vegetation in a deep red hue to slow the spread of flames. Jeff Emery, President of Global Fire Safety at Perimeter Solutions, says the vivid color is intentional.

“The reason that the color is so critical for a pilot is all about visibility,” Emery explains. “It was more usage than we've ever seen in a January.”

But concerns about safety have resurfaced. A 2024 University of California study found that one earlier version of the product—Phos-Chek LC-95-W—contained enough heavy metals to qualify as hazardous waste under federal and state guidelines.

Daniel McCurry, an associate professor of civil and environmental engineering at the University of Southern California, says there’s good news. “The Forest Service phased out Phos-Chek LC-95 nationwide as of the end of last year,” he confirmed.

Today, the U.S. Forest Service uses a different version—Phos-Chek MVP-FX—which Emery says is primarily composed of water, ammonium phosphate (the same compound used in many fertilizers), a thickening agent, and red coloring.

Preliminary research on the new formula is encouraging. “This product is supposed to be cleaner,” McCurry says, “and that seems to be the case from what we can tell.”

Perimeter Solutions says it's committed to ensuring the safety of its products. “We feel very good about the safety of Phos-Chek MVP-FX,” the company said in a statement.

The U.S. Forest Service also clarified that the older LC-95 version was never used or loaded at airtanker bases in California and emphasized that their safety standards are constantly evolving.

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