WHAT IS CAF (Compressed Air Foam)?
Basically a combination of water (commonly used in firefighting), soap (referred to as foam concentrate) and compressed air – all mixed together and designed to make water a more efficient and effective firefighting agent.
Why the Soap?
The soap, most commonly referred to as Class A Foam Concentrate, has one main function in CAF and several other benefits when mixed with water. The main need for the concentrate in CAF is to allow the air and the water to mix. Without the concentrate, air and water cannot mix together.
The other benefits of mixing the concentrate with water:
For more information, click on Class A Foam!
Why the compressed air?
Water has the ability to absorb a lot of heat (9300 btu’s/lb). However, as water is applied to a fire in drops, only the outer portion of each drop absorbs the heat. A large amount of the water passes by or through the fire, resulting in water damage. By pumping air into the water, each drop is blown up to a bubble forcing the entire drop to the exposed surface. This expanded “surface-to-mass ratio” (SMR) allows the entire drop to instantly absorb its full capacity of heat. No excess water passes through the fire – the fire goes out much faster and water damage is virtually eliminated.
What is the actual affect?
By fighting fire with CAF, fully involved house fires have actually been extinguished in as little as 30 seconds using as little as 40 gallons of water. Most fires could actually be extinguished with small total amounts of water if the water could be applied effective enough for all of the initially applied drops to absorb the heat. Since water by itself is not applied effective enough form, large volumes are required, resulting in high run off and water damage. CAF application is effective enough to result in immediate heat absorption, thus resulting in the lower total water usage and damage.
Does it actually work?
Unequivocally – YES!
How
does it work?
As mentioned above, CAF knocks out fire faster due mainly
to the increased Surface-to-Mass Ratio (SMR). Expanding water drops into bubbles
increases the SMR. Bubble expansion can be low, medium or high. Aspirating
nozzles will expand water into higher SMR bubbles. The benefit to using CAF over
aspirating nozzles is the long distant, high energy stream for reach; combined
with the expansion into small uniform bubbles that provide a stronger, longer
lasting bubble than can be produced by aspirated bubbles.
Foam solution is liquid drops; the SMR is the same as
water. The benefit to Foam Solution over water is the decreased surface tension
and it will adhere to carbon better than water. Most fog nozzles will break the
Foam Solution in to smaller drops, increasing the SMR some what above water,
however, Foam Solution is still in drop form and can pass through the fire
wasting the water and causing damage. Foam solution also does not have the
vertical holding capability to coat walls. Foal Solution will immediately run
off of vertical surfaces. CAF is superior to Foam Solution in that the
compressed air expands the water to its maximum SMR, allowing it to immediately
absorb heat and practically eliminate water damage. With the strong uniform
bubbles, CAF can also cling to vertical surfaces.
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