For our brave men and women in the fire service, there are a few sudden hazards that can arise with little to no warning. Backdrafts, flashovers, BLEVEs, and brush fire wind shifts can either ruin a day, maim, or even kill with ease. But a hidden danger is potentially lurking at even the most basic and routine automotive fire calls: major magnesium parts on our cars.
Most of you don’t know that I, before going into finance, was a firefighter for five years. The VERY FIRST car fire I went on as a cadet involved an old VW Bug in the parking lot of a Circle K convenient store. And boy, was it burning! “Fully involved”, as we might say. My Lieutenant threw on his gear WITHOUT a mask/SCBA (air tank), grabbed a hose, and marched confidently/haphazardly/moronically up to the fiery back of the Beetle. As soon as he opened the nozzle up on the inferno, the following basically happened (someone else’s video of someone else’s nonchalant death-defying screw up, same principle):
BOOM went the magnesium engine block! It sent the LT running away, unscathed only by the grace of God, and embarrassed that he didn’t know better. Witnessing that incident was a better learning event than any class or training activity I’ve ever gone to since. For the record, I’ve also seen the same thing happen with magnesium wheels (but with a better firefighting approach/no moronic attack).
The chemists reading this will know exactly why this happened, but for everyone else, let’s break this down to a very simple explanation as to WHY squirting water on a magnesium fire can be a bad thing: when magnesium (and all materials, really) gets hot enough, it releases flammable vapors that obviously combust at the proper temperature and mix of gases. When magnesium burns, however, it does so at temperatures as high as 4,000 degrees Fahrenheit. When water hits the magnesium at this temperature, it splits the hydrogen and oxygen apart. Hydrogen’s ignition point is 932º; combined with a fresh batch of newly-available oxygen, we get said BOOM.
So if water makes it explode, how would a fire department put out a fire like this? With ALL THE WATER. Literally, I mean. In order to put out any fire, you must lower the temperature and/or take away the oxygen. Emptying a fire truck’s tanks onto an engine block-sized magnesium fire will eventually lower the temperature of the fire and drown the fire out. From experience, it’s also the most entertaining fire to put out, considering we got a fireworks show to go along with the excitement of a car fire.
Magnesium is lighter than aluminum, which makes it still a favorite of auto manufacturers desperate to either increase the performance or efficiency of their vehicles by taking out every pound from curb weights that they can. From Chrysler Pacificas to Aston Martin Valkyries, F-150s to Mercedes AMG-GTs, magnesium is still being incorporated into both bodies and drivetrains. And that’s a net positive for us all, too!! The lighter the vehicle, the better!
Just be sure to keep back if it catches fire.