Engine Company, Firefighter Training, Firefighting

Comparing Apples to Apples: Gps vs. Jps

Issue 5 and Volume 169.

For years, we’ve all heard the mantra of gpm (gallons per minute) vs. Btus (British thermal units). We’ve heard and seen this so many times that it must be true, right? Although this axiom has served us well, and I couldn’t agree more with the tenet that sufficient water puts out fire, the truth is that it’s not entirely accurate. Comparing Apples to Oranges So why am I throwing stones at this long-held adage? Because it’s inaccurate and the math is wrong. When we compare gpm to Btus, we’re comparing apples to oranges. A simple change in our terminology can both enhance our understanding of fire behavior and reinforce the importance of speed on the fireground. To clarify, Btu measures the energy produced by the fire, whereas gpm refers to our fire flow, or the power absorbed by the water. Power (P) equals the amount of heat energy (E) per…

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