A fire extinguisher is one of those household items considered an absolute necessity but also one which you hope never to have to use. While it may remain in a corner, forgotten for years, this fire fighting device could end up one day, saving your property and even potentially, your life.
In order to understand how fire extinguishers operate, it’s essential to have a look at the basics of fire itself. Resulting from a chemical combustion reaction, fire normally occurs from a reaction between oxygen and a fuel, such as wood. This combustion reaction only happens when the fuel is heated to its ignition temperature, so this means the three factors that interact are oxygen, fuel and extreme heat. This is where fire extinguishers step in − playing the role of removing at least one of these factors so that a fire is suppressed.
So what exactly do fire extinguishers consist of?
They are robust metal cylinders containing water or a smothering material which, when you press on a lever at the top, is released under high pressure. Inside there are several mechanisms at work. For starters, in some extinguishers, a plastic siphon tube runs from the bottom of the extinguisher to the top, while a spring-mounted valve blocks the passageway from the siphon to the nozzle. At the top of the extinguisher lives a small cylinders of compressed gas and a release valve prevents the gas from escaping.
In the case of a fire, pull out the safety pin and press on the operating lever. This causes the lever to push down on a rod, which then pushes the spring-mounted valve down to open up the passage to the nozzle. The compressed gas escapes, thus asserting downward pressure on the fire-suppressant material, which will drive the material out of the nozzle with a great force.
Remember these steps:
- Pull the lockpin out;
- Aim the nozzle at the base of the flames;
- Squeeze the handles together; and
- Sweep from side-to-side at the base of the flames.
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