ModuSec panels have a steel skin with an almost 100% closed cell core and tongue and groove joints that are sealed with a silicon mastic. The doors have the same structure with 4 sided double rebated frames fitted with 2 smoke/water seals. Service entry points are also protected from water ingress. These features provide protection against fire fighting water and leaks. Additional sealing measures can be taken in areas that are in danger of extensive flooding. For external rooms, a pitched roof is provided with gutters and downpipes (the walls need no further protection).
The virtually closed cell core prevents moisture or water spreading within the panels, with no significant drop in strength, insulation and fire protection over time and no risk of structural damage from water.
Note that plasterboard is porous and can allow the transmission of water in a leak or flood situation with possible ceiling collapse to follow or replacement of partition walls being required. Mineral wool is also porous - the level being dependant on density.
Brick, block, concrete and plasterboard will give off steam when heated during a fire, producing harmful humidity levels for IT hardware and media.