For data center fire suppression, this can be a tricky issue. Which is more dangerous? Which might hurt my IT equipment?
Having either system is not dangerous, and is much more desireable than no protection. In this comparison, both are assumed to be ‘dry’ pipe systems, and therefore not a threat to IT equipment due to the most prevalent IT risk – human error. Upon activation, a gaseous system will not damage equipment, and some owners will choose gas based on this factor alone. A water mist system is not a threat unless the mist system is activated for a prolonged period, at which the micro drops of water begin to collect and become actual water droplets. Actually, the larger water droplets aren’t much of a threat either, unless you happen to have your equipment exposed instead of within typical server or blade cases. These days, tinkering with equipment like that is just not done as much, let alone running with it out of the case for a prolonged period. In a water mist system, the micro drops are about 25-200 microns, and due to the behavior of water at this small level it will not be conductive to make a short circuit on computer equipment as readily.
One of the big factors is also cost. FM200 and similar systems definitely have an advantage in cost for data centers with less volume, perhaps up to about 2,000 square feet. But at about 4,000 square feet, the cost advantage begins to weigh much more in favor of a water mist system. This is because the mist system typically has a pump, no matter the size of the data center, that is included in the cost. As the size of the data center increases the gaseous suppression system just balloons to match the volume needed.