Supression is not life safety, Its main intent is property protection.
I've seen water mist work very effectivly. Very popular in the power industry for the gas turbines. It must be very well calibrated, (air/water mix).
The new data rms, paper is not protected, rather the electronics. This is the reason behind the gasses.
Halon is still out there. the systems can still be recharged, (if you can find and afford it). The systems can not be modified, no athaurity will honor the calculations.
Fm-200 ( AKA FE-227) Is the replacement. All new calcs and modifications are needed so basicaly a new system.
Halon takes 13 million yrs to break down, FM takes only 9 million.
A nice product out there is "Inergen", The draw back is it takes up a lot of space.
This is an inert gas combo. @ 2500 psi it must be throttled down on discharge.
It operates by displacing the room air with the gas (+- 80%)
It drops the oxogyn level to +- 12% and raises the co2 level to +- 8%, This will susstain life (no PI) but not support flame.
Due to the percentage pres. releif must be present (like dropping an ice cube in a glass, the excess (rm. air) has to be moved out. Hence the need for space, all those tanks.
dis claimer: I've been out of this end for 3 yrs, some things are newer, and my % may not be exact.
I may be going back to it soon coz it's one exiting feild.
