Are fog nozzles not the answer?
What we are talking about is a simple fact (no matter what name is used). When liquid water undergoes a physical change at 212°F from liquid water to a gas (steam), this process absorbs 941 btus/pound of water. This amount of heat must be retained by the steam to remain a gas. Now we come to the critical fact about the vaporization of water. This process, this change of state, does not increase the temperature of the steam above 212°F. I don’t believe that Fredericks realizes the extreme importance of this fact. In other words, if the right amount of water is applied to a fire, then this water will absorb all the excessive heat being produced by the fire, and the temperature of the steam remains at 212°F. It is not superheated.
To be sure this saturated steam at 212°F is dangerous enough to fire fighters. However, as Bill Nelson states on page 109 in the section on EFFECT OF EXPANDING STEAM
However, if proper size lines are used and handled in the proper manner, the products of combustion and steam forced into remote areas will be cooler than those originally being forced there by the fire.”
This leads to Nelson’s conclusion that was previously quoted. It should be obvious to anyone that the use of fog nozzles rests upon a solid scientific foundation.
There is one final issue discussed in Part One. Fredericks states:
Misapplication of Royer and Nelson’s methods began almost immediately .For example, the concept of managing heat—using the thermal balance within the fire area to advantage—was quickly lost on many practitioners of the combination attack.”
Fredericks then begins to speculate on the reasons why this misuse happened. He also enlists the help of David Fornell in this speculation. However, none of this speculation comes close to the real reason why fog nozzles were widely misused.
Bill Nelson in QUALITATIVE FIRE BEHAVIOR has perhaps the best statement on this issue. (See p. 100).
“…Tests were run and discussion and arguments were heated during the 1950s. About 1960, the pendulum swung. Fog became fashionable for all fires in most fire departments and the fire service was plunged into a dark decade of thermal imbalance. Buildings continued to burn while fog streams flowed. Slowly fire fighters learned that fog was a useful tool, but needed to be carefully used if it was to save more buildings than it lost. Certain stubborn individuals continued to point out that straight streams used properly were just as effective as fog and usually did not cause thermal imbalance problems.”
How true. So how have fog nozzles been misused to produce thermal imbalance problems?
The answer is very simple and very basic .Bill Nelson has made the following statement (page 102) that is perhaps the most profound statement ever made about the use of fog nozzles.
“In principle, fire fighting is very simple. All one needs to do is put the right amount of water in the right place and the fire is controlled.”
Thus to use a fog nozzle properly, or carefully, you must use the right amount of water. How do you misuse a fog nozzle? Use too little or too much water. It is as simple as that. While it should be no surprise that using too little water is a weak attack that has little effect upon a fire, what may be surprising is that using too much water is counterproductive. Common sense might tell you that using more than enough water will simply gain control of the fire quicker, but not so.
