THE VOLUNTEERS CORNER
EXCEPT for a five-bagger, probably the hottest thing in the fire service today is high-expansion foam. Although the list is growing, relatively few departments today are using this foam, and we do not have wide experience in using this new medium on the fireground.
It is this lack of experience on the application and behavior of high-expansion foam that makes it difficult to decide how to enter this new field of fire fighting. Perhaps a review of the available equipment and some suggested standards for judging its usefulness will help you reach a decision.
There are several foam generators on the market that look somewhat like a smoke ejector. The mixture of foam liquid and water is pumped to the generator, where it is sprayed in front of a fan. It is then blown by the fan through a coneshaped piece of mesh cloth. The fan is operated by an electric motor, so in addition to getting hose lines in place, you have to hook up a power line—either to a portable generator or to a truck with a 110-volt outlet.
The other type of foam generator is entirely hydraulic. The foam liquid and water mixture enters the center of the generator in a multitude of closely spaced, fine jet streams. The force of the jet action thrusts the resultant spray through a mesh cloth to create high-expansion foam. In the all-hydraulic models, you can get a unit that is known as a “foam nozzle” and is as portable as a nozzle with an applicator attached. Or you can get models that are like the electricmotor foam generators in size.
Once in use, the larger foam generators cannot be moved until they are shut down. Then it is a two-man job to move them on the fireground. However, the volume of 1000 to 1 high-expansion foam generated runs as high as 3500 cfm, according to the manufacturers.
The foam nozzle, on the other hand, has a rated 55-gpm maximum capacity with over 100 to 1 expansion rate. It provides some 700 cfm of high-expansion foam.
This is one of the points at which you have to stop to make a decision. I’m a strong advocate of the precept that every fire department must make equipment decisions within the framework of its own territory characteristics and fireground experience. What is likely to burn in your area? What has burned in your area in the past? What would have helped you do a better job? These are the questions that must be answered before you can reach a useful decision on equipment for your department.
Will it probably be more important for you to have portability in high-expansion foam equipment, or will it be more sensible to provide for the highest possible volume of application per minute? Within the range of high-volume application, will the need for electricity to operate some generators have an important effect on the time required for extinguishment?
These are questions that you should give a lot of thought to before making a decision. In some cases, you might wish to carry a couple of types of equipment to cover all situations. Regardless of how you decide, there will be times when you’ll probably wish you had more equipment.
However, high-expansion foam offers one great advantage to the volunteer fire departments, which usually are not large enough to carry sufficient supplies of protein foam. High-expansion foam can buy you a great deal of time.
Using 3 percent protein foam with a 50 or 60-gpm nozzle, a 5-gallon can of foam liquid last no more than 1 2/3 minutes. If you carry a maximum of four 5-gallon cans on a pumper, you must extinguish the fire in less than 7 minutes. If there is a lick of flame left, the fire will regain its intensity and leave you helpless.
Now, 6 or 7 minutes do not give you much time for calling in an adequate supply of foam to handle a large foam job. You may have to load cans on a truck or you may have to ask another fire department to send foam liquid. This takes time.
Let us, then, take a look at high-expansion foam which, incidentally, has a detergent base. This is educted into the hose line at a 1 percent rate. At a water flow of 50 gpm, this means that a 5-gallon can of high-expansion foam liquid will last 10 minutes. If you carry four cans, your firstdue pumper can maintain one foam line for 40 minutes—or two lines for 20 minutes. This gives you a comfortable margin of time for getting more foam from outside sources.
One of the characteristics of the highexpansion, detergent-base foam is that it is less stable than protein foam. And this is one reason why you may want to call on outside sources for additional foam. You may have a large flammable liquid spill that should be kept covered with foam for many hours after extinguishment to provide sufficient time for proper disposal of the flammable liquid.
Here is something else to think about: Would you be likely to have situations that require a final foaming with a longstability blanket of protein foam? If you might, then find out if the high-expansion foam you choose is compatible with protein foam. This can be a definite problem. You might wind up watching incompatible detergent and protein foams tearing themselves down to a lost promise. Take time to try out foams before you load up with something you can’t use.
Another field for high-expansion foam is structural fires. We’ve hardly explored this area on the fire ground, but we are learning.
One of the questions you have to answer is how large a volume of foam per minute will be satisfactory for most jobs.
The answer is going to depend on the types of structures in which you will fight fires. To give you some guides for reaching a decision, let’s look at the problem of volume and space.
Let’s suppose that you have a fire in a cellar that is 8 feet high, 25 feet wide and 100 feet long. That’s a total of 20,000 cubic feet. How quickly do you think you ought to fill this area with foam? If you generate 3000 cfm of foam, it will take 6 2/3 minutes from the moment you make foam at the 3000-cfm rate.
Apply this system of comparing foam generation volume per minute to the average volume of areas that might bum in your territory and you’ll get a pretty good idea of what foam capacity to shoot at. You may wish to start off with a couple of generators.
I’ve seen many demonstrations of applying foam in buildings, but I haven’t heard much about some of the pitfalls. First of all, there is no guarantee that the place w’here the foam enters will give a free passageway for the foam to flow throughout the fire area. You may be putting foam into a partitioned area with closed doors that will keep the foam from flowing to other burning rooms.
If the fire gets into walls, false ceilings and other concealed spaces, the foam has no way to chase after the fire and fill these places. Your fire could travel up a wall unless you take the usual steps to get to the burning materials.
You can walk through high-expansion foam, but you can’t see anything. You can breathe without any extra difficulty as far as the foam is concerned. However, it is recommended that self-contained breathing apparatus be used for more comfort and protection against dangerous gases. Without breathing apparatus, if you cup your hand in front of your nose, you will prevent the foam bubbles from getting into your nostrils and you’ll find it easy to breathe.
What makes high-expansion foam so interesting is the fact that it offers unexplored possibilities for firemen. I’m sure that you will see foam equipment improved in the years ahead, and we will find more and better ways of using it.