wildfire magazine




In May of this year, USDA Forest Service Chief Randy Moore put a 90-day moratorium on all prescribed burns on lands administered by the forest service, following the Calf Canyon/Hermits Peak fire in New Mexico that started after prescribed burn operations. With this moratorium came a hard internal look at new tools and procedures that could help to make prescribed burns safer and with less risk of escape. One of the not-so-new tools is the use of phosphatebased long-term fire retardants, a technology that has been safely used for decades by forest service and fire professionals, but that is gaining significant attention for expanded use as part of prescribed burn plans.

As the U.S. government and communities look to reintroduce the beneficial use of wildfire into the landscape, long-term retardants are helping to make the burns safer while protecting critical assets. Fire management agencies are incorporating the use of long-term retardants to reinforce control lines by applying it on both sides of the lines to reduce the chance of escape. Long-term retardant is also being used around homes and outbuildings to create a firebreak in the fuels leading up to each structure, and on vegetation to maintain a habitat for wildlife after the prescribed fire.


The USDA Forest Service established what was called the 10 a.m. policy in 1935, which required that every fire should be suppressed by 10 a.m. the day following its initial report. Other federal land-management agencies quickly followed suit and joined the campaign to eliminate fire from the landscape. According to the website foresthistory.org, these strong measures to suppress fires have resulted in ecosystems that have developed, primarily, through a dominant influence of fire exclusion. These ecosystems are characterized by longer “fire return intervals” and long-term changes in forest structure and composition. These changes have resulted in significantly larger numbers of trees per acre, more biomass in brush species, more dead and down vegetation, and a dominance of fuel ladders. All of this has contributed to larger, more intense fires resulting in much greater resource damage and unacceptable permanent ecological changes.

In 2021, Pheasants International, in collaboration with a Midwest power company, used long-term retardant to treat around high voltage power lines in advance of a prescribed burn. Individual polygons of vegetation were treated or left untreated to allow for diversity in existing pheasant habitat. Photo by Perimeter Solutions.

Fire suppression efforts were later aided, in the 1960s, by the development of new technologies, such as fire suppression chemicals. It was much later that fire managers started to realize the positive role fire played in forest ecosystems. This change in attitude led to advancements in USDA Forest Service policy in the 1970s. Prescribed burns became more prevalent and land management plans began to include both prescribed burns and “managed wildland fire” as strategic objectives. The use of long-term retardant as a tool in prescribed burning also became more prevalent.

Examples of this use are plentiful. The Shasta Trinity National Forest, as well as many other land management agencies, starting in early 1980s, carried out a widescale program of “block broadcast burning” as a silvacultural tool after timber harvest to prepare sites for planting. Long-term retardant was applied on log decks, wildlife trees and slash piles to keep them from igniting and creating subsequent containment concerns.

In addition, in 2007, prescribed burns were conducted in Hawaii to eliminate the invasive species of Gorse (Ulex europaeus). To protect the sensitive soil profile and the viewshed from residual visual effects, long-term retardant was used for control lines; this eliminated the need for either bulldozer lines or handlines resulting in less impacts to soils.

Starting around the beginning of the 1990s, firesuppression efforts had to account for the growing wildland-urban interface (WUI), the area where developed land occupied by homes and businesses intersects with the natural environment. The use of long-term retardant, in a preventative manner, can assist in preventing escapes and reduce potential impacts.

According to the College of Natural Resources at North Carolina State University, between 2011 and 2019, the use of retardant in forests and rangeland areas around the country increased by 28 per cent, and in 2019 prescribed burns were used to treat more than 10 million acres in the United States.

The USDA Forest Service conducts an average of 4,500 prescribed burns every year, and, according to its website, plans to increase that number over the next 10 years; this will include an additional 20 million acres on National Forest System lands, and up to an additional 30 million acres of other federal, state, tribal, and private lands.


Recent advancements in long-term, ground-applied retardants complement the introduction of prescribed fire back onto the landscape. Retardants can be applied days or even weeks ahead of the prescribed burn on cellulosic material, including utility poles or railroad infrastructure, live fuels, as well as dead and down flammable vegetation. After the retardant dries on the vegetation, it is effective until it is physically removed by up to a quarter of an inch or more of rain. Due to the durability of long-term fire retardant, it can be applied well in advance of the initiation of the prescribed burn project; this becomes especially important when weather and smoke dispersion issues postpone the prescribed burn ignition. As weather conditions are prone to change in the days and weeks leading up to an actual burn, application of the longterm retardant helps to reduce risk of fire escapingcontrol lines. In addition, long-term retardant assists in keeping the prescribed burn within containment lines during post burn conditions, when low humidity, high temperatures and unexpected winds return to the prescribed-burn site

Long-term fire retardants are available in colored and uncolored form. Uncolored retardant is nearly clear, while the colored product is bright red and fades to earth tones after exposure to sunlight; this allows prescribed-fire managers to select the product that best meets the visual requirements of the project.

In 2021, Pheasants International, in collaboration with a Midwest power company, used long-term retardant to treat around high voltage power lines in advance of a prescribed burn. Individual polygons of vegetation were treated or left untreated to allow for diversity in pheasant habitat. The retardant also protected the cellulosic poles, while fireproofing most of the flammable vegetation under the lines. This application proved to be very effective and demonstrated the environmental and ecological benefits of using longterm retardants to help maintain the wildlife habitat.

In addition to the ecological and environmental benefits of using long-term retardants as part of prescribed burns, there is a significant element of risk reduction that can be provided to communities, homes, and valuable assets that are within or near the intended burn area. As the prescribed fire location is being prepared, 20- to 100-foot defensible barriers can be placed around homes, buildings, communication towers and other valuable infrastructure. Retardant may also be used to keep the burn away from sensitive or threatened habitat, important trees (relic stands such as Sequoias) and other ecologically important landscapes. Old-growth trees can be protected by applying retardant on top of their root structure and at a certain distance up the bole of the tree. Application of retardant to the surrounding vegetation will help maintain soil productivity by protecting microbial life and enhancing nutrient cycling necessary for the health of retention trees..

Long-term fire retardants are a proven successful solution that helps to establish or reinforce control lines, prevent fire escape, and
protect critical assets within or outside the burn area, improving the safety of firefighters and the public. Photo by Perimeter Solutions.

Environmental organizations have been major proponents of reintroducing fire into the landscape, and have used ground-applied, long-term fire retardants in some prescribed burns to protect ground cover around trees. Discussions are ongoing with environmental leaders about how to safely and effectively apply retardant around many groves of trees as part of future burns. The use of phosphate-based retardants is better for the environment than other solutions, as the residual phosphate that is left after the burn will provide nutrients for soil health and plant uptake. Targeted application of retardant on native vegetation, and avoiding application in and around invasive plants, will favor native species over invasives; this helps to provide sustainability in favor of desirable endemic species.

The retardant lines that are applied from the ground and placed in advance of the prescribed burns work the same as the red fire retardants dropped from air tankers on an active fire. The products can be surgically applied by use of ground equipment such as water tenders, type 3/6 engines, hydroseeders and spray equipment that is in the back of vehicles or in spray trailers. In many cases, aerially applied fire retardant is applied just ahead of the active fire to help render the vegetation non-flammable and give firefighters on the ground time to establish adequate firelines on the other side of the fuel. In a prescribed-burn scenario, once the firelines have been constructed, retardant can be applied on the fuels located on both sides of the firelines; this serves to provide an additional layer of fire safety to the burn by preventing short range spotting and slopovers (burning over established lines) and reducing the probability of escapes. Critical assets can be further protected by applying retardant around their perimeter.

In July, long-term fire retardant was used in a prescribed burn by Atascadero Fire and Emergency Services in California. The burn was close to housing, utility infrastructure, and roads, which the municipal fire department wanted to protect. Battalion Chief Dave Van Son said after the burn, “The application of PHOS-CHEK® FORTIFY® long-term fire retardant ahead of the burn gave us an added layer of confidence that the burn would be conducted safely, while at the same time demonstrating that the preventative and proactive application of the product could be valuable in helping to prevent roadside ignitions as well as under utility infrastructure.”

We believe the preventative application of longterm retardants will become standard procedure for prescribed burns, agency administrators, and prescribed fire managers, and that burn bosses will be encouraged to incorporate this affordable tactic prior to or during many prescribed burns, as the cost of failure – in even one per cent of burns – will be measured by the societal cost of loss of life, property, and resources.

In both prescribed burns and in wildfire suppression activities, long-term retardants can be used to establish and enhance safety zones. The establishment of safety zones is an important part of firefighter safety. The size of safety zones and deployment zones has been a continual discussion point in the fire service; in many fuel types, a tremendous amount of ground must be cleared to mineral soil. The use of retardant can serve to increase the size and survivability of these zones.

The resource damage from wildland fire is well understood. A recent example of such negative impacts was seen on the McKinney fire on the Klamath National Forest in northern California, where tens of thousands of fish were killed from sediment and ash loading in the streams. Prescribed fire has potential to also cause significant impacts to valuable aquatic resources. Retardant can help to mitigate such impacts by careful application near waterways. A significant advantage of these treatments is realized by precision application with ground resources. Unlike aerial assets, the buffer zones for ground application are far less and governed by local jurisdictions’ statutes and county ordinances; this can create a situation in which the treated fuels and organic litter are left intact on the soil to assist in filtering ash and sediment.

Having the ability to use the best fire retardants in the industry from any ground-based equipment is a tremendous advantage to fire agencies. Things don’t always go according to plan, and prescribed fires always present an inherent level of risk. Experience has demonstrated that escapes will occur. Agencies conducting prescribed burn programs should readily have, and use, all tools available to them to adequately mitigate risk. Long-term fire retardant is one of those tools that should be in the box to help reduce and, in many cases, eliminate bad outcomes.

The tragic events surrounding Calf Canyon/ Hermit’s Peak fire brought national attention to prescribed burn programs, and it has led the USDA Forest Service to reexamine how it conducts prescribed burns. While the agency pauses and considers options, and reviews new technologies, it is important that it take advantage of a solution it has relied on for nearly 60 years. Long-term fire retardants are a proven successful solution that helps to establish or reinforce control lines, prevent fire escape, and protect critical assets within or outside the burn area, improving the safety of firefighters and the public.


Ron Raley serves as agency liaison for Perimeter Solutions and has worked in wildland fire management for 53 years, spending 35 years with the United States Forest Service. He finished his career as the deputy director of fire and aviation management for the Pacific Southwest Region. While with the USFS he held numerous positions on incident management teams, including service as a type I incident commander dealing with complex incidents across the country