Dowse that Fire with Carbon Dioxide!
Written by Dr Klaus L E Kaiser
Firefighting used to be simple. In the olden days, water was all that was needed and (hopefully) available as required. Once structures came with charged electrical wires, water was no longer the material of choice. You might extinguish a small fire and electrocute yourself in the process.
As of late, with high voltage (~700 V) electric vehicles that problem has been catapulted to new heights. For example, a recent report on the entire set of 18 competition e-bikes having burnt to ashes is just an inkling of the problems with that technology.
You Ain’t Seen Nothing Yet
The point at hand, however, concerns the ability to extinguish fires, of nearly all kinds, in the most efficient way and the newly proposed regulations by European Union bureaucrats. I find it even difficult to believe that anyone would intend to ban CO2-type fire extinguishers “to save the climate.” What a crazy idea. In my humble opinion, that idea really borders on criminal insanity!
When water was no longer the ideal choice, science came up with a simple substitute for water. That material was highly effective and could be used to fight fires of nearly all kinds of flammable materials, except for some very special fire problems, such as ignited metal shavings.
That new material was widely available, is constantly produced in million ton quantities all around the world and was much more effective than water as well. It works well on burning liquids and solids, can safely be used on electric systems, and is self-pressurized.
Furthermore, this material not only extinguishes flames in a great hurry, it provides a strong cooling effect on the burning substance(s), which is an important part of extinguishing a burning substance. That is because this liquid in the extinguisher, upon release to the atmosphere undergoes adiabatic expansion.
That process volatilizes a part of the material to gas (which suffocates flames) and cools the other part to a solid white snow. The snow has a temperature of -70 C and provides a strong cooling effect to any burning liquid or solid.
As a consequence of both flame-smothering and cooling effects, that fire-fighting material does “the trick” in a hurry. That great firefighting material is called carbon dioxide (CO2).
But that’s not all, CO2 as fire extinguishing material has other great advantages over other systems.
CO2-Type Fire Extinguishers
Carbon dioxide based extinguishers are common in places were a quick and effective response may be required. For example, when I was a student in a chemical lab, another student and the supervisor were working behind me on a glass apparatus with hot flammable liquid. For some reason, the glass broke and the liquid caught fire with an audible whoosh.
I did not need to see what had happened behind me, I could hear it. As I was working on a similar experiment myself, I had already placed the lab’s fire extinguisher right beside me. When I heard the sound of breaking glass and burning liquid, I simply grabbed it, turned around and dowsed my colleagues who had fallen or tripped over each other and were lying on the floor in burning liquid with a short blast of CO2-snow.
It saved both from any lasting effect. That event happened more than 50 years ago and is still “burnt” into my memory.
I couldn’t imagine a chemical laboratory without such a fire-fighting device on hand.
So, let me just briefly review the main advantages of CO2-based extinguishers:
- They are always “on”, that is they do not need a separate pressurizing gas and are refillable
- Their readiness can quickly be ascertained from just lifting and/or shaking it; the weight or feel of the liquid inside will tell you if there is still much fluid present
- Even upon use (even repeatedly), there is no danger of the valve seal (as in the “modern” sodium bicarbonate powder extinguishers) clogging with a solid that tends to lead to complete loss of the pressure after one use
- As already mentioned, the very cold CO2 not only smothers flames (by displacing the air and replacing it with non-combustible CO2 ) but also strongly cools the burning substance
- Their use does not leave behind any (chemically aggressive) powder and, therefore, does not affect the continued use of electronic gadgets.
Modern Dry Chemical Fire Extinguishers
Most modern dry chemical extinguishers are suited for A, B, C type fires. If not all, most of such dry chemical extinguishers use sodium bicarbonate powder which is dispensed by pressurized nitrogen or air. That’s why such extinguishers have pressure indicating gauges that are to show if the extinguishers are (more accurately, are thought to be) still good to use and, generally come with an “expiry date.”
That doesn’t mean that they couldn’t expire earlier by loss of the compressed gas or, if the gauge were to become corroded and failing, still indicating a (no longer factual) good performance and having become useless instead.
The EU bureaucrats’ idea of “saving the climate” by doing away with small handheld CO2-base fire extinguishers is worse than asinine — I can only think of it as a kind of eco-terrorism that will surely backfire.
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