The following is designed to assist you in making a CAFS (Compressed Air Foam System) purchase. The information contains key points to consider and is not an all-encompassing guide.

Why Purchase CAFS?

Convincing the folks who control the purse strings of the need for a CAF (Compressed Air Foam) apparatus purchase is sometimes a daunting task. If CAFS is in the apparatus replacement plan, it may simplify things, however, be prepared to do your homework if you need to justify a CAFS purchase. The importance of all parties buying into CAF before purchase cannot be overemphasized. Compressed Air Foam is an effective tool that makes plain water up to five times more effective and improves fire fighter safety. Simply put, CAF makes extinguishment happen quicker and safer. With those two points, one can build a number of convincing strategies for CAF. Additional CAF benefits include: Increased stream reach, less fatigue (lighter hose), faster fire knockdown, reduces heat rapidly, reduces property damage, reduced overhaul, fewer rekindles, protection of exposures, evidence preserved, faster cleanup, and reduction of fire companies on scene time.

Define The Mission

What will be the mission of the apparatus: Brush Fire, Quick Attack, Extrication, Haz. Mat, Structure Attack or other? Does the apparatus have a single mission, or must it perform multiple missions? An apparatus that must perform several missions may require a compromise between mission.

CAFS Basics

Back to basics: What is a CAFS? When Class-A concentrate is added to water, the result is an improved water for fire fighting. This mixture lowers surface tension, allowing water to penetrate and wet class-A fuels. The mixture is also attracted to carbon, attaching onto the products of combustion, instead of running off as with plain water. Simply adding a foam concentrate proportioner to an apparatus will increase the units fire fighting capabilities.

There are three items needed to produce CAF: Water, foam concentrate and compressed air. CAF is high-energy foam. The compressed air is injected into the water and foam concentrate solution super charging the foam at the nozzle discharge. CAF produces foam with a superior bubble structure. In contrast, aspirated foams are low energy foams that introduce air into the water and foam concentrate mixture at the nozzle. Some of the water energy is used to generate the foam. Less available energy produces foam with a shorter reach with a less durable bubble structure.

Water pumps are the foundation of today's fire fighting apparatus. Be sure the pump is fire service rated and meets the needed flow requirements. The pump should be sized for anticipated water only attack. Water still puts out the fire. The cooling of the water stream must exceed the BTUS produced by the fire.

The rotary screw air is the standard for most of today's CAFS. Rotary Screw Compressors have a track record of proven reliability with low maintenance requirements. Generally one cubic foot of air is required for each gallon of water; however, this can vary depending on the user needs. A one cubic foot of air to two gallons of water will make wetter foam, and foams with airflow ratios higher than water flow will be dryer. Wet foams are better for fire attack. Dry foams, in certain situations, may be better for structure protection.

The foam concentrate porportioner is a critical component! The foam proportioner must accurately meter from 0.3 to 1.0 percent of class A concentrate at all water flows. A proportioner that cannot do this will not produce good CAF. The FoamPro Series Models 1600, 2000 and Darley Fast Foam meter accurately at all water flows. The FoamPro units are electronic direct injection systems calibrated to the gpm water flow of the discharge. The 1600 model will handle water flows at 0.5 percent up to 340 GPM of water. The 2002 Model will handle water flows at 0.5 percent up to 1000 GPM. The Darley Fast Foam is a balanced pressure venture proportioner. This simple reliable unit is ideal for portable pump applications such as "skid units" or "drop in" units, but is also good for jump line applications on pumpers. The 1600, 2000 series and Fast Foam are more than adequate for most wild fire and structural apparatus applications. FoamPro also builds higher flow proportioners for larger water flows. Class B foams can also be proportioned with these units.

If A and B foams are used on the same apparatus, a system to keep the two concentrates separated is a must. Some A and B concentrates are not compatible when mixed, and will produce a grungy mess that will clog the foam system. FoamPro makes an A-B foam system that water flushes between foam uses.

Powering The CAFS

How the pump and water compressor are powered may depend on how the apparatus is used. Pump and roll units generally work best with a separate engine driven power source, and stationary pumping units work well powered by the main drive engine. Stationary pumping units CAFS can be powered through the PTO or main drive transmission. Some units are even powered under the hood linked to the engine through belts or other methods. A CAFS required to do pump and roll, with the main drive engine, is sometimes difficult to operate. The CAFS water pump and air compressor will usually have a minimum and maximum rpm requirement. These engine rpm requirements may lead to a ground speed too fast, for hand-line crews to walk, or limit the ground speed of the apparatus when pumping. The separate drive engine allows the CAFS to operate independent of the drive engine. Structure engines are probably the best application for CAFS powered by the main drive engine.

Points To Ponder

The Gross Vehicle Weight, GVW, of the apparatus must take into account the weight of the combined water, equipment and hose carried. Emergency response vehicles operating at maximum Gross Vehicle Weight Rating, GVWR, will not perform and handle as well as one slightly under the upper GVWR rating.

Is the apparatus required to meet a standard such as NFPA 1901? Vehicles meeting standards such as NFPA will add to the total cost. Be careful of a manufacturer with low prices that do not meet any required standards. An example of an apparatus bid catch all may be written: "Must meet or exceed the Standard (IE NFPA 1901) unless otherwise specified." The "meet or exceed" allows the manufacturer some flexibility, and the "otherwise specified" allows some flexibility for the purchaser, if he decides to exempt an item from the Standard. Keep in mind some Standards like NFPA are drawn up by a committee in which compromises are made, and some parts of an article may hinder rather than help your specific situation. The manufacturer may require the purchaser to sign a liability release for each exception. Be careful if exceptions are made, as you could be held liable in the event of an injury or death. Don't compromise safety!

Talk to Departments who have CAF Units. Find out what they like and what they would do differently with their apparatus. Ask manufacturers about references of trucks they have sold. Do they have demo a truck you can operate? Look for ease of operation. Getting CAF out the nozzle should be a simple operation. Before purchasing the apparatus, be sure the manufacturer will provide operation and maintenance training at your department.

Retro-Fitting An Existing Apparatus

Odin Foam specializes in retro fitting existing apparatus to CAF. This can save considerable money over purchasing a new CAF apparatus. By adding an air compressor and a foam proportioner, most fire apparatus can be upgraded to produce CAF. Odin Foam can evaluate your apparatus for feasibility of a CAFS conversion.

If You Have Questions

Darley/Odin builds Compressed Air Foam Apparatus ranging from light-weight skid units to Type 1 Class A Pumpers. All units undergo rigorous testing before leaving the factory. We are committed to building quality user friendly Compressed Air Foam Systems and would be happy to answer your questions concerning CAFS. Odin Foam can be contacted at odinfoam.com or 877-634-6223