Are fog nozzles not the answer?
These facts give the proper perspective to judge Fredericks recommendation. A minimum flow of 150 gpm is far too excessive for control of a 2,000 cubic foot fire. The inevitable result is a massive disruption of the thermal balance that exists in a fire. It should be obvious that Fredericks recommendation is not the answer.
The only answer is the proper use of fog nozzles. Such use does not cause any thermal imbalance problems. Only improper use of fog nozzles causes these problems by using too much water. In other words, I dispute Fredericks claim that “violent disruption of the thermal balance is characteristic of the indirect and combination methods.” This is not true. Fog nozzles used properly with the right amount of water do not cause thermal imbalance problems.
What constitutes the proper use of fog nozzles: There are four tactical requirements.
- Adjust the reach of the stream so that it just reaches across the room
- Adjust the flow to provide a rate-of-flow near the ideal rate.
- Distribute the little drops of water evenly throughout the fire area (clockwise rotation)
- Shut the nozzle off when the flames disappear and white condensing steam appears.
By contrast the solid stream nozzle can do only one of these tactical requirements.
- The reach is fixed, cannot be adjusted, and extends too far for most rooms.
- The flow rate is fixed with a ball type shut-off valve that must be opened fully.
- With a narrow slug of water it is extremely difficult to distribute the water evenly.
There is another huge difference between a solid stream nozzle and a fog nozzle. The rate of absorption of heat by water is directly proportional to the surface area of the water. At a droplet size of 0.01 inch diameter, the little drops of water have a surface area 1,4000 times greater than a solid slug of water of the same volume. Thus a fog nozzle is more than 1,000 times more efficient than a solid stream nozzle in absorbing heat.
