By Lou DeRosa for Fire Chief

The Madison (N.J.) Fire Department has employed compressed-air foam systems since 1998, and they are used on every fire the department responds to today, replacing the plain water used in prior years. But though CAFS is being used in all aspects of the fireground, it is not a magic potion. Rather, it simply is a powerful, efficient and effective tool that, when used properly, offers tremendous extinguishing advantages and increases the safety of the firefighters who use it.

Why would a fire department choose not to invest in CAFS? Perhaps the additional cost is the discouraging factor. Perhaps it is because CAFS is not fully understood. Or maybe the reason stems from fear of change or the unknown. Based on experience, it seems that the reasons most departments do not invest in CAFS extend beyond just dollars and cents. The most likely cause of such reticence is that many fire departments do not fully comprehend the tremendous advantages and options available to them with such systems. Many fire service personnel simply do not understand the inherent inefficiency of using plain water. Firefighters work so hard to get water onto the fire only to realize that only a very small fraction of what flows is effective in extinguishing the fire.

Let’s examine the inefficiency of plain water as an extinguishing agent and compare it to foam solution. Does water work as an extinguishing agent? Yes, eventually it does, provided that the flow is sufficient to meet or exceed the critical application rate and that it flows for an ample amount of time. However, water has a distinct disadvantage — high surface tension. High surface tension signifies that the water does not readily absorb into the surface on which it is applied, i.e., most of the water that is applied beads up and runs off the surface.

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