1. CAFS On-Line Orientation
Montgomery County
Fire & Rescue Service
Class A Foam Theory

2. Class A Foam Theory
 MCFRTA 2008

3. Objectives
The user will be able to utilize the proper terminology when refering to finished foam and its ingredients
The user will be able to list the ingredients of Class A Foam
The user will be able to list the benefits of Class A Foam for use in suppressing Class A Fires
The user will have a very basic understanding of how CAFS is made
The user will be able to state the benefits of Class A CAFS for use in suppressing Class A Fires
 MCFRTA 2008

4. Foam Terminology General Terms Foam Concentrate
Foam Concentrate Injection Rate (Proportioning Rate)
Foam Solution
Finished Foam
Foam Types

5. Practical Foam Terminology
Foam Concentrate
(As Purchased From The Manufacturer)
+ Water =
Foam Solution
+ Air & Mechanical Agitation =
Finished Foam
(Air Aspirated Foam Solution)
 MCFRTA 2008

6. Foam Terminology
Mixing & Finishing - where is the air added and where does the agitation occur?
At Nozzle = Nozzle Aspirated Foam System (NAFS)
At Pump = Compressed Air Foam System (CAFS)
 MCFRTA 2008

7. Foam Types Foams are typed by the fires they are designed to put out.
Class A Fires need Class A Foam
Class B Fires need Class B Foam
For CAFS MCFRS will be using Class A Foam only.
You will learn about Class B foam later; for now we will concentrate on Class A foam.
 MCFRTA 2008

8. Class A Foams Ingredients: Foaming Agent (Creates Bubble Structure)
Wetting Agent or Surfactant (Decreases Surface Tension of Water) - this means that the water will soak into the material.
Emulsifying Agent (Breaks down Molecules containing Carbon (example - Charred wood) “oleophillic” - this means that the finished foam wants to bind with the burnt materials.

9. Class A Foams
Class A Foams have different proportioning rates depending upon the application the agent is being used for :
Normal Range - 0.1% (one-tenth of 1 percent) up to 1.0%
This means that using a 0.5% (five-tenths of 1 percent) Class A foam concentrate proportioning rate will use 5 gallons of concentrate for every 995 gallons of water.
Nozzle Aspirated Foam
0.3% - low expansion, 1.0% high expansion
Compressed Air Foam
0.3% - “Wet”, 1.0% - “Dry”

10. How do I Make CAFS
There are a variety of ways to power the components, but all CAFS systems have three basic systems which must work together.
 MCFRTA 2008

11. CAFS Triangle
These are the components that work together to make CAFS.
Air Compressor
Foam Pump
Water Pump
 MCFRTA 2008

12. Advantages of CAFS
Because of the addition of compressed air, fire streams have increased reach & penetration (high energy).
The finished foam has increased “soaking” ability.
The finished foam clings to vertical surfaces increasing contact time of the water.
Because of the addition of air hose lines are lighter.
More efficiently uses water
 MCFRTA 2008

13. Wet CAFS vs. Dry CAFS Refers to the proportioning of air to water
The more air, the dryer it is
Can also be affected by “richness” of foam mixture
If you add more foam concentrate, the finished foam will be dryer. At full dryness, the foam concentrate proportion automatically gets kicked up to 1%.
 MCFRTA 2008

14. The more air - the “dryer” the foam
Wet to Dry - Controlled by amount of air
“Wet”
“Fluid”
“Dry”
The more air - the “dryer” the foam
 MCFRTA 2008

15. Review Questions
List what the following ingredients of Class A Foam do and explain why they help us put out Class A fires:
Surfactants
Emulsifiers
Foaming Agents
List the three parts of the CAFS triangle:
List the components of finished foam:
How does CAFS differ from NAFS?
 MCFRTA 2008