What agent to use? That´s quite a question, just type "FM200 vs inergen" on the Google to figure out thousands of diverse comments and information (but of course, following the respective Murphy´s law you´ll only see information that is not specifically the one you are looking for).
Our experience, after reading lots of literature and vendor comments, tells me that, to have a real answer, if possible, ask for a quotation of the system and a preliminary design of each type of agent, also read impartial information like the related chapter of the SFPE handbook, the NFPA 2001, etc, before you read the vendors information.
I can add some personal comments:
-If considering FM 200 also consider Ecaro 25 FE25 (check Fike) and similars that are in the market.
-Inergen in some cases require a design concentration that in certain conditions can be dangerous (so be careful when you hear that inergen is much safer than FM200 for example).
-If life in atmosphere is an important issue, be very cautious when reading the environmental information of each agent.
-FM 200 and others are low pressure tanks, Inergen and others are high pressure tanks.
-Manufacturers make the refilling process a delicate issue that may need special tools, knowledge of the control system, and some kit (o rings, rupture disks, etc.)so be careful when they say that refilling the tank is easy. For example, vendors say that inergen tanks can be refilled everywhere, but be careful and confirm with quotations of the complete service, of course that depends a lot of the place where you live, etc. (specially check costs when the system requires a detecting rupture disk).
-Some companies offer agent "banking" services, so refilling and maintenance can be cheaper.
-Some vendors say that direct discharge on delicate equiptment is dangerous or that the residues are corrosive, etc., be careful with that comments.
-CO2 still is a good option for many applications, don´t exclude it easily.
-The control system is very important, a very expensive gas system needs a good initiating and control system.
-Somebody mentioned me that, in average, a systems suffers an accidental discharge every 3 years, I haven´t checked if this is true but think what would happen if that come true for you.
-Ask first what would happen if you install a first class detection and anunciating system instead of a gas system. So only install a gas system when really needed.
-Water sprinklers are still loved by fire authorities and insurers, so sometimes water mess costs can be "tolerated".
-There are agents designed specifically to overhaul old Hallon instalations (like FE 25).
-Avoid confussion with the comercial names of the different agents, vendors always try to make the difference, FM200, Inergen, Ecaro, etc. are commercial names that have other brand equivalents or similars.
-There are aerosole systems (fine powder based) that can work as well as gas systems for some conditions and for some applications are much better. They state that they are safe for electronic delicate systems, but I haven´t seen a strong documentation to support this (if somebody finds one please post it).
Hope this helps.
ps. A little real experience: We have an installation (little control room of a power plant in Costa Rica) with FM 200, they had an accidental discharge with 8 guys inside, while programing the control panel. Only two suffered little reactions as light head aches, other noted some eye dryness, all liked the "mint" scent as they discribed it. Thank God, they hadn´t previously talked with an Inergen vendor, or they would have surely died!.
The plant operators realized that the insurance company does not have an specific requirement for the gas system, so after checking the cost of the refilling of the system, it was not in their priorities and unfortunately the system is still empty until it can be included in the budget.
