In harsh environments involving high temperatures, heavy particulates, oil, or chemicals
capable of damaging components, ambient air must be kept out of the enclosure. Sealed
enclosures are generally used, with closed-loop cooling consisting of two separate
circulation systems in a single unit. One system, sealed against the ambient air,
cools and recirculates the clean cool air throughout the enclosure. The second system
uses ambient air or water to remove and discharge the heat.