Summit County deals with pink fire retardant left after Buffalo Mountain Fire |

Summit County deals with pink fire retardant left after Buffalo Mountain Fire

An air tanker drops Phos-Chek fire retardant on the Tenderfoot 2 Fire, September 18, 2017 in Dillon. Phos-Chek remains in Mesa Cortina after the Buffalo Mountain Fire last week.
Hugh Carey /

“Better a pink house than no house,” quipped Summit Fire & EMS Chief Jeff Berino at a community meeting last week. Berino was referring to complaints about fire retardant dropped by air tankers on the first day of the Buffalo Mountain Fire that turned some homes and streets in Mesa Cortina a rusty, bubblegummy hue.

While Berino didn’t wind up receiving many gripes about the pink “slurry” in the days since evacuation orders were lifted, he understands why residents might be concerned about its health, environmental and aesthetic impacts. To that end, the county has been trying to let residents know what it is and how to get rid of it.

The chemical fire retardant used on the fire last week goes by the brand name “Phos-Chek,” manufactured by St. Louis-based Perimeter Solutions. The product, a liquid concentrate mixed with water, is approved for use in the wildland by the U.S. Forest Service. Phos-Chek is dropped ahead of fires, not on them, to stop their progress toward homes and structures.

The distinctive coloring is intentionally added to make it easier for pilots to spot for targeting purposes. Other trade-secret performance additives make Phos-Chek easier to disperse from aircraft while making it heavy enough to land with precision. The largest air tankers used last week, geared-up DC-10s known as Very Large Air Tankers, or VLATS, were dropping over 8,000 gallons of the Phos-Chek mix on each pass. The exact amount of material dropped during the fire won’t be known until accounting is done for the county’s after-action report.

According to a Phos-Chek fact sheet, its main fire-retarding ingredient is ammonium polyphosphate, an organic salt that also sees industrial use as a fertilizer.

When it lands, Phos-Check reacts with wood or other organic cellulose material. The reaction disperses the oxygen fires need to keep burning. As the treated wood gets hotter, instead of combusting, the wood develops a black charred shell that keeps oxygen from coming in or out.

If a large enough area is Phos-Chek-ed, the treated zone becomes a barrier between the wildfire and whatever it is protecting. The wildfire, with nothing to burn and nowhere else to go, suffocates, weakens and becomes much easier for firefighters to control.

Once the fire is out, Phos-Chek remains in the wildlands until it is washed off naturally by rain. The runoff dissipates into the ground and actually becomes a kind of fertilizer that helps forest regeneration later by boosting nitrogen and phosphates in soil. The color fades away over time, too.

As far as how to get it off houses, cars and streets, Chief Berino said all it needs is a good washing from a regular garden hose, and sooner rather than later as the material can bake onto surfaces. However, both Berino and Perimeter Solutions advise that residents not try to power wash the clay-like material off homes. Power washing will just push Phos-Chek deeper into porous surfaces, like wood and concrete, and may never come out, permanently pinking exteriors.

Dillon District ranger Bill Jackson assures the community that the material is safe for the environment and not toxic, but just like organic chemical fertilizers, it’s not something people or animals should consume. Runoff should not be allowed to collect in pools, as pets and other animals might try to drink it. For any further questions about the fire retardant, its safety and removal, contact the Summit County Department of Environmental Health at 970-668-4073.

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