How does a fire nozzle work?
Our previous article gave a brief overview of the Halligan bar, the tools of firefighters trade for forcible entry. Now we will take a quick look at an indispensable gear used after the doors are breached — the fire nozzle.
Firefighters will typically have to carry approximately 45 kg of equipment — particularly the fire hose — to commence firefighting operations from a doorway, which may be several floors above ground level. But let’s not forget that it’s the nozzle at the end of each fire hose making it possible for firefighters to complete their mission safely and efficiently.
As important as hoses, fire nozzles by design have the characteristics such as handiness, durability, and suitability. In consideration of all these elements, we’ll talk about the basic types of nozzles and provide a general overview of their reliability, utility, and functionality.
Before touching upon a fire nozzle’s suitability based on certain circumstances, it is important for us to understand how fire does the job. To ignite a fire, three requirements need to be met: fuel, heat, and oxygen. The fuel can be defined as any flammable agents or materials, ranging from wood to gasoline.
Heat energizes the fuel and vibrates the atoms of which it is composed. As the vibrations grow intensified, atomic bonds break apart so that the fuel is vaporized. Fire is created by such a chemical reaction between these vapors and nearby oxygen.
The reason why water is widely used to put out the fire is that it takes time for water to boil, which means water tend not to be changed as the temperature changes. In other words, water molecules vibrate only when the hydrogen bonds (H2 in H2O) break apart, which consumes a considerable amount of energy. Therefore, spraying water on a fire (non-greasy) can take the fuel’s heat away tremendously by interrupting the chemical reaction on which it depends.
Firefighting, however, is more than just spraying as much water on a fire as quickly as possible. Qualified firefighters need to ask themselves the following questions based on different situations:
How far can water travel?
How well can the stream go through materials on fire?
Can water take away heat and smoke from the fire scene by air currents it creates?
Is desired water pressure available?
Is the fire scene cool and safe enough for forcible entry?
Will the stream harm people trapped inside the building on fire?
Taking all these elements into consideration helps firefighters to choose the right nozzles and then avoid mistakes caused by improper tools.
To master the nozzle as a firefighting gear, a firefighter has to know its output, which varies in three major ways as follows:
discharge/gallonage rate (gallon per minute)
Water pressure determines not only how far and how fast water can be sprayed from the nozzle outlet, but also how deep it can be injected into burning materials. For anyone fighting fires, the more gallons of water he can get, the more likely he can extinguish the fire by cooling its fuel.
All this hinges on the type of nozzle he uses, which has a desired, or rated, gallonage at a rated pressure (60 GPM at 100 PSI or 50 GPM at 110 PSI).
A nozzle can produce different stream patterns, depending on the situations on the fire ground. For example, fog nozzles can produce a cone-shaped stream formed by tiny water droplets, which can be conveniently converted into streams to take away heat from the surrounding air or hot air out of an enclosed area.
Straight streams are produced for long reach and deep penetration, but not a good choice for protection and ventilation.