Halon 1301 and Halon 1211 are/were wonderful fire fighting agents. They are among the banned gasses per the EPA Jan. 1 1994 except for use in Aircraft firefighting systems.
Both worked great with some differences. The flood systems use 1301 as it is self discharging from its own pressure and is lighter and works better inside an enclosed space.
1211 is heaver so it carriers further and is more persistent in an outdoor fire such as may be found in a aircraft engine on the flight deck, it does require a propellant to give it some throw distance from the extinguisher so some of the weight is not agent but a propellant. This is the gas used in handheld extinguishers.
Halon is NOT corrosive and not a hazard to human life even in an enclosed space, it is used in computer and electronic facility's to prevent unnecessary damage to millions of dollars worth of equipment when discharged.
They work by disrupting the chemical chain reaction of the fire and are the reason that the old fire triangle is now a tetrahedron.
Halon 1211 and 1301 is no longer available and systems can only be serviced using the existing gas inside them. No refilling as they are considered a ozone depleting gas. they have been replaced with a less effective gas requiring more agent and a much greater cost. The only 1:1 replacement gas I know of is AF11E there is another product called Halotron 1 that is somewhat of a replacement but not using the same systems you have now.
Halon is still used in aircraft extinguishers.
Keep your FireBoy halon systems protected, replacement cost is a shocker.
Regards,