Many enclosures have an air supply for cooling; this supply should be filtered. Some enclosures do not have an air supply but should. If the interior is much warmer than ambient and the cabinet contains electronics, then the cabinet should probably have air or other cooling.
The air exchange might be passive, relying on convection from heat generated in the enclosure. Or it might be achieved with forced ventilation.
Sometimes forced ventilation is achieved with plant air, which is an expensive resource. If using plant air, you need something to remove the oil before air enters the enclosure; during a repair, this device should be checked. It is generally better to use an intake fan, exhaust fan, or both; the supply air might be ducted from another space or it might be picked up near the enclosure. Typically, the intake is near the bottom, and the exhaust vent is near the top.
Most airflow cooling systems have an intake air filter. This should be checked during any repair and replaced or cleaned, as necessary.
