Is the gas reactive? Or is it located within a corrosive environment?
Reactive Gases: Nitric Oxide (NO), Nitrogen Dioxide (NO2), Ammonia (NH3), Hydrogen Sulphide (H2S), Sulphur Dioxide (SO2), Hydrogen Chloride (HCl), Chlorine (Cl2) or semi conductor gases such as Silane, Diborane, Phosphine, Phosgene, Arsine etc.