All total flooding systems that are internationally approved for use in occupied spaces are safe for use if the systems are both designed properly and then installed correctly strictly according to the hydraulic calculations and iso designs.
In terms of which extinguishing agent to select; inert gas systems and clean agent (FM-200 and Novec-1230) systems are all acceptable for use in server room environments. (Of course I exclude CO2 total flooding - as CO2 really should not be used for occupiable spaces on safety grounds).
According to industry data:
The extinguishing agent with the widest safety margin between design concentration and LOAEL is Novec1230. Safety Margin in excess of 50%
Next is FM-200. FM-200 is a propellant used in inhalers used by asthma sufferers. Safety Margin is approximately 10%
Last are the inert gases which have a safety margin below 10%.
However, Unlike Chemical Agents, Inert Gases will not create breakdown products on exposure to a surface in excess of 500 deg C - but if the Clean Agent systems are installed and designed correctly this becomes a non-issue.
Inert Gas systems are high pressure discharges that displace up to 40% of ambient atmosphere to reduce oxygen levels sufficiently. The displaced atmosphere needs to be vented through wall vents to avoid over pressurization and damage to people and property. If the server room is an internal room then the venting needs to be cascaded wall to wall until the pressure can be vented to outside the building.
Inert Gas systems typically require 6 - 8 times more storage space than a clean agent system (needs more 4-6 times the cylinder capacity than clean agent) and also requires high pressure discharge pipe and fittings.
Clean Agent systems require schedule 40 pipe and fittings.
Inert Gas systems are low cost to refill as the extinguishing gas "per kilo" is low cost.
Clean Agent systems are higher cost to refill as the extinguishing gas is significantly more expensive.
Inert Gas systems being high pressure can be installed further away from the hazard area as they have enough pressure to "push" the gas over a longer distance.
Clean Agent systems (the cylinders) being smaller and lower pressure tend to be installed in the hazard area or in an adjoining room ie nearer by.
All Total flooding systems should be released following a pre-alarm which permits occupants to vacate the area prior to discharge. This is normally a 30 second delay following "2nd knock".
Apart form total flooding systems there are also "in-cabinet" solutions available that detect and suppress fires inside/on the particular fire hazards. These systems use the same clean extinguishing agents as the total flooding systems but instead of total flooding rooms the systems are much smaller and are designed to protect the individual server racks, cable ducts, switch gear etc rather than the entire room. AS such these present a smaller or no impact on any occupants.
Hope this is useful.
