In some environments, an area with a high humidity will require a tile designed to withstand this. Please note that no tile is actually waterproof, although there are tiles that are designed to withstand a high level of humidity and as such are best suited to shower areas, swimming pools, salons & kitchens etc.
Many ceiling tiles that are not designed to withstand a high humidity can be adversely affected by the moisture in the air, causing a distortion of their shape. In extreme cases, tiles may visibly sag and may even fall out of the gridwork.
For use in humid areas we recommend products with at least 90% humidity resistance, though there are a range of affordable products with up to 100% humidity resistance. In aggressive environments like swimming pools, it is also preferable to utilise a non-corrosive grid.