Electrical equipment mounted on the exterior of a pressurised enclosure must be explosion protected in accordance with the Zone (or EPL requirement) in which the enclosure is situated. Typical examples are pressure/flow rate sensors or switches which may use Ex I equipment, and junction boxes using Ex d, Ex e or Ex n methods of protection. This requirement also applies to the motor and starter of the fan which provides the flow of air, unless they are situated in a non-hazardous area (which is preferable).
