How do fire extinguishers work
Extinguishing agent - pressure generation - triggering
The extinguishing agent contained in the fire extinguisher is expelled by overpressure and released directly into the fire. A distinction is made here between permanent pressure extinguishers, which generate pressure using a propellant gas in the extinguishing agent container, and charging extinguishers, where the pressure comes from a separate external or internal propellant gas bottle, and gas extinguishers (mostly CO2), where the extinguishing agent is also a propellant gas.
The effectiveness of a fire extinguisher depends crucially on correct handling. In principle, only incipient fires (for example in the case of waste paper bins, televisions, computers, etc.) can be fought successfully. As soon as the fire has spread within a room, it develops so high temperatures and poisonous smoke gases that fighting with a fire extinguisher is no longer possible.
Simple symbols on each fire extinguisher describe how it is put into operation. Every fire extinguisher has a secured release device. In most cases, it is a yellow safety tab fastened with sealing wire, which prevents the fire extinguisher from being switched on unintentionally. After pulling off the tab, a push button may have to be pressed on rechargeable extinguishers. When the operating lever on the hose or directly on the housing is triggered, the extinguishing agent flows out. The extinguishing beam must be aimed at the source of the fire.
Extinguishing agents have the task of extinguishing burning substances, taking into account their fire class and the prevailing environmental conditions (e.g. danger to people or room size).
Every extinguishing agent has a main extinguishing effect and possibly secondary effects. The wrong choice of extinguishing agent can have fatal consequences. For example, extinguishing a fat fire with water can cause a fat explosion. Since burning fat or oil is already several hundred ° C hot when it ignites, added water evaporates suddenly. Due to the explosive evaporation, the burning fat is torn out of the container with the water vapor, with mostly devastating effects for the extinguishing agent and the environment.
Permanent pressure extinguisher
Permanent pressure extinguishers are devices whose extinguishing agent is under permanent propellant pressure.
The propellant exerts constant pressure (so-called permanent pressure) on the extinguishing agent. If the triggering device is actuated, the extinguishing agent is expelled via the riser pipe and the injection nozzle.
In the case of charging extinguishers, the extinguishing agent is only pressurized when it is put into operation.
The charging extinguisher consists of 2 containers, namely the extinguishing agent and propellant gas container. If a connection is established between the two containers, for example by opening the valve, the propellant gas flows from the propellant gas container into the extinguishing agent container, which is thus "charged".
It is the most reliable way of securing the propellant gas pressure because the propellant gas containers can be checked for leaks for a long enough time before they are installed. You can also replace them during inspections without any problems. The propellant that can be stored in an internal propellant cartridge or external propellant bottle is carbon dioxide (CO2).
A gas extinguisher is a fire extinguisher that consists of a container. The extinguishing agent is both a propellant and a pressurized gas in terms of the Pressure Vessel Ordinance.
The release devices on fire extinguishers must be secured and sealed. If the seal is defective or the fuse is missing, it must be assumed that the fire extinguisher is no longer ready for use.
Duration of function
The duration of the function is determined by the time the extinguishing agent is released in seconds, in which the extinguishing agent is expelled when the outlet cross-section is fully open. The duration of the extinguishing agent delivery depends on the filling quantity. Usually the duration of the extinguishing agent delivery is overestimated. A standard extinguisher with a supply of 6 kg of extinguishing agent is empty after about 10 seconds.
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