Are fog nozzles not the ans
The Efficiency and Effectiveness of Fire Combat
Why are fog nozzles so much more efficient and effective than smooth bore nozzles? There are two reasons. First, Liquid water must be projected with sufficient velocity near the burning fuels to be vaporized. This is extremely difficult to do with a smooth bore nozzle that projects a solid slug of water with a stream far too great for any size room. Water will travel through the fire at high velocity, hit a wall or ceiling, and splatter back. This creates a lot of turbulence (thermal imbalance) with a mix of hot and cold areas in the room. The water is completely out of control.
The fog nozzle, on the other hand, is highly efficient in distribution. The reach of the fog stream can be adjusted to the width of the room (no splattering). Moving the nozzle in a systematic way (clockwise rotation) distributes the water throughout the room evenly. The result is that all the water is turned to steam in a few seconds. The sudden appearance of white condensing steam expanding out of the room signals a cooling below 212°F. The fire is under control. Efficient distribution is the first key to the superiority of fog nozzles.
This means that if the surface area is doubled, then the ability of water to absorb heat is also doubled.The second key is the little drops of water. The ability of water to absorb heat is directly related to the surface area of the water applied into the fire. The correct math term is “directly correlated”. This means that if the surface area is doubled, then the ability of water to absorb heat is also doubled. In other words, the ability of water to absorb heat increases just like the surface area. The smallest drops of water produced by a fog nozzle are 0.01 inch in diameter. If the drops were all 0.01 inch in diameter, then the surface area of the little drops from a fog nozzle would be 1,400 times greater than the surface area of the solid slug of water from a smooth bore nozzle! That is truly amazing.
As far as efficiency is concerned, the little drops of water increase the efficiency by a ratio of 10 to 1.The diameter of some of the drops is somewhat bigger, but they are still little drops of water. Let’s take an average to account for the bigger drops, say 1,000 to 1. This ratio is still difficult to comprehend, but it is true! About the only thing you can say is that the little drops of water far exceed the ability of a solid slug of water from a smooth bore nozzle to fight a fire. As far as efficiency is concerned, the little drops of water increase the efficiency by a ratio of 10 to 1. That is, the amount of water needed is reduced from 100 gallons to 10.
Also a 10 to 1 ratio is probably correct for effectiveness. In other words, the fire is controlled in seconds rather than minutes. If a fog attack can be completed in 10 seconds, then ten times is 100 seconds, or one and 2/3 minutes. This latter time is for a smooth bore nozzle.
No one type of nozzle, or tactic, will be able to solve all of your fire fighting problems.In view of all these facts, it is difficult for me to understand why the use of a fog nozzle should not be preferred over the use of smooth bore nozzle for confined structure fire fighting. Remember the 1,000 to 1 ratio. That fact alone should be sufficient to make a choice. There is one warning, however, to keep in mind. “There is no magic pill”. Those are the words of Keith Royer that I have heard stated many times. No one type of nozzle, or tactic, will be able to solve all of your fire fighting problems.
