what (chemical )gas is used in the production of fire fighting foam?

Answer 1

Easy answer, none. Foam is created by the use of a foam concentrate and a air aspirating foam nozzle, not a gas. The nozzle has a feed tube that pulls foam concentrate into the nozzle where it is mixed with the water supplied from a hose.

If you have a special fixed system such as used in an aircraft hanger or petrochemical tank, the foam is stored in a large bladder tank. The foam concentrate is mixed into the water before hitting foam nozzles or sprinklers.

Concentrate is most commonly 1% or 3%. It can be high expansion or low expansion. The percent is the amount of foam to water mix you will design the system to deliver. The proportioners and nozzles should be designed for that percent or foam. Most all foams these days are chemical foams. But in the early days of foam systems we used a lot of protein foam. Most commonly made from rendered animal parts mixed with other chemicals.

Answer 2

Do you have a waste-basket handy? My ex was a fire-fighter for a while, and he told me that the first foams were made of pureed fish guts. They effectively block air from feeding the fire. (He wasn't kidding at the time.)

Answer 3

There are many compositions some of them patented.

Here is one MSDS sheet that lists the composition of one of them:

http://www.fs.fed.us/rm/fire/wfcs/products/msds/foam/forexpan.pdf

Answer 4

Carbon(iv)oxide