Decades of Committed Research
In 2021, a new magnesium chloride-based fire retardant was granted conditional qualification on the USFS Qualified Products List. The makers of the product touted their solutions as “new” and “innovative”, but the reality is that the use of magnesium chloride as a fire retardant has been researched for more than 80 years, and this research has determined that ammonium phosphate and numerous other chemicals (including boric acid) are more effective than magnesium chloride as a fire retardant.
1940: University of Idaho Study
In 1940, research was conducted at the University of Idaho on the “effectiveness of certain chemicals in decreasing the combustibility of sawdust.” They published their findings, basing their results on the loss in weight of the sample during testing. The decreasing order of effectiveness of the chemicals studied proved to be as follows:
- Diammonium phosphate
- Monoammonium phosphate
- Zinc chloride
- Ammonium sulphate
- Ammonium chloride
- Magnesium chloride
The researchers went further, stating, “The first four of these were effective in moderately small amounts (8-10 percent), and may be used to fire-proof sawdust. Larger amounts of ammonium sulphate and ammonium chloride are required, while magnesium chloride is not suitable as a fire retardant.”
1954: Operation Firestop
In 1954, the USFS created Operation Firestop – the first major study to look at firefighting effectiveness. Taking place at Camp Pendleton Marine Corps Base Camp, it was designed as a one-year feasibility study. Its purpose was to explore the behavior and build-up of mass fires and to develop and demonstrate on actual wildfires some new attack methods that arose from science and technology that evolved during World War II.
One phase of Operation Firestop tested the effect of fire-retardant chemicals on the ignition time of wood, on the fire intensity of burning wood, and the ability to suppress flaming wood. The study covered many chemicals that had been in use over the previous decades in firefighting products. The table below summarizes these chemicals relative to overall performance in this study.
Several important revelations resulted from this study. (Table 1) First, it was apparent that phosphate chemistry was the most effective in reducing the impact of fires. At the same time, it was evident that chemicals, such as magnesium chloride, boric acid and polyvinyl acetate were not effective. As a result, phosphate chemistry was on its way to becoming the standard for fire retardants.
Table 1 - Effect of Various Chemicals on Fire Intensity - 50 Percent of Fuel Treated*
*The intensity and peak ratios are determined by dividing the total heat output or peak heat output of treated fuel fires by comparable data from untreated fires.
1970: The Blakely Report
In 1970, University of Montana Scientist Aylmer D. Blakely presented a paper entitled A Laboratory Method for Evaluating Forest Fire Retardant Chemicals. This time, 14 chemicals were selected for use in this study – many of which had been the subject of the previous retardant studies referenced above. (Table 2)
Blakely developed a new system for evaluating the fire retarding ability of chemicals to give reliable and easily interpretable information. Blakely based his analysis on (1) fuel weight loss, (2) the amount of radiation emitted, and (3) the amount of residue after all combustion had ended as the fuel burned. Based on these three measurements, Blakely developed what he coined the Superiority Factor Method to measure and rank effectiveness.
TABLE 2: Chemicals Tested in 1970 Blakely Study
- Ammonium chloride
- Ammonium phosphate (dibasic)
- Ammonium phosphate (monobasic)
- Ammonium sulfate
- Boric acid
- Calcium chloride
- Magnesium chloride
- Magnesium sulfate
- Phosphoric acid
- Potassium carbonate
- Potassium chloride
- Sodium tetraborate
- Sodium silicate
The overall ranking of chemicals (Table 3) showed that diammonium phosphate, monoammonium phosphate, phosphoric acid, and potassium carbonate consistently ranked higher than any of the other chemicals in all three parameters – with diammonium and monoammonium phosphate ranked at the top overall.
This study confirmed the results from Operation Firestop that phosphate chemistry offered the highest effectiveness for fire retardancy and positioned these as the chemistry of choice for the industry in the years ahead.