Last week we discussed the combination fog nozzle and how it broke the stream of water into little droplets, thus using steam conversion to cool and extinguish the fire. This week will look at an older style nozzle that is still popular in many departments -- the smooth bore.

Last week we talked about the science of fire, why the application of water extinguishes fire, and one of the more common nozzles utilized to apply water to the fire.

Before we get into a second popular nozzle used in the fire service I need to make the “purist” happy and clarify something from that article.

Since we were talking about how water is used to extinguish a fire I used this older model of how fire burned — the Fire Triangle: Fuel, heat and oxygen.

There is, however, a more recent model taught — the Fire Tetrahedron, adding a fourth item needed, Chemical Chain Reaction. So now you know and all the fire instructors in the world are happy!

Last week we discussed the combination fog nozzle and how it broke the stream of water into little droplets, thus using steam conversion to cool and extinguish the fire. This week will look at an older style nozzle that is still popular in many departments -- the smooth bore.

The smooth bore nozzle has been around since water has been pumped through hose to fight fires. Where the combination nozzle broke that stream of water into small droplets, the smooth bore leaves that stream in place, undisturbed until it reaches its destination then breaks into large droplets of water.

One of the more popular arguments for the use of this type of nozzle is the reach and penetration of the stream. As a solid stream it carries more force allowing the stream to reach the seat of the fire with larger volumes of water. However, since the water pattern is not broken it will not absorb as much heat as its counterpart, the fog nozzle.

One of the benefits of this style nozzle is that it takes much less engine pressure to move the water from the truck to the end of the hose.

This reduction in pressure offers several advantages to the equipment and the firefighters. First it makes it easier for the hose to be handled by the firefighters at the nozzle.

Going back to science class think about Newton’s Third Law of Motion, for every action there is an equal and opposite reaction. So if it takes more force to push water from a fog nozzle than a smooth bore nozzle that also means there would be more back force on that hose line, back force that the firefighters on the end of the line would have to manage.

More force equals harder work thus making a hard job and fatiguing your firefighters quicker. Additionally more pressure being produced by your truck means that truck also must work harder to produce water at the nozzle at the correct pressure.

It is hard to define the differences between these two nozzles in a couple small articles, books have been written on the advantages and disadvantages of each of these. You can say now that you do have a basic understanding fire, how water extinguishes fires and how we get the water onto the fire.