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What Is Fire Retardant & How Does It Work?

Updated: Jan 25, 2021

Here at 10 Tanker, we’re constantly seeing our fleet on nightly news stories across the nation. Needless to say, the demand for video footage of our tankers dropping red substance over an area engulfed in fire has not decreased. However, for some the age-old question "what is this red stuff?" remains.

First, it's important to understand how wildfires are caused. A typical combustion reaction requires some kind of spark, fuel, and oxygen. A spark can come from something in nature like a bolt of lightning, but more likely it'll come from humans. With dried wood, moss, and plants everywhere fuel and oxygen are no scarce resource for a fire to get started.

When it comes to extinguishing these fires, dumping an enormous amount of water is an effective approach in several ways. First, water interferes with a combustion reaction, because as it evaporates, it creates a layer of water vapor that separates the fires fuel from the atmospheric oxygen that keeps it going. Second, the water cools the fuel which slows and ultimately extinguishes the reaction.

A major component to forest firefighting are Aerial assets dumping water from the sky, and firefighters working on the ground to create " firebreaks''. Which is exactly what it sounds like a break between the fire and its fuel. Crews cut out a border of vegetation between the fire and surrounding land helping to contain the fire and prevent it from spreading.

Unfortunately, aerial water drops, and firebreaks aren’t enough when combating large scale fires. So, here's where that "red stuff" comes in. Fire retardant we use is called PHOSCHEK, and it is made up of primarily ammonium polyphosphate, water, fertilizer type salts, a coloring agent, corrosion inhibitors, and flow conditioners. It's a long-term fire retardant which means it can be sprayed on an area and unless it gets washed away by a rainstorm it'll stick around for months.

How does fire retardant work?

Another thing to understand is that the fire retardant isn't dropped directly on the fire, in reality it's dropped just outside of it to create a containment perimeter. PHOS-CHEK retardants work in three ways removing heat, coating the surface (so the fuel can't find oxygen), or by diluting the air near the fire. The retardants react with wildland fuels altering their route of decomposition in a fire so that they do not support flaming or glowing combustion. The rate of flame spread is reduced and can be dramatically decreased while a slow burning is allowed. The reddish color serves as a visual aid for pilots and firefighters on the ground. After a few days of exposure to direct sunlight, the color will fade and eventually disappear.

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