Axial Axial type fans cause gas to flow through in an axial direction which is parallel to the shaft where the blades rotate, making the flow axial at exit and entry. Axial fans are designed to create a pressure difference and force which produces a flow through the fan. 21 ltr/s extraction rate Building regulations stipulate that extractor fans need to be able to extract at least 15 litres of air per second. It's needed to ensure a minimal build-up of moisture in the room, reducing mould and grime in damp areas. This fan will extract a crazy 21 litres per second! That's 1.5x what's recommended! Zone 2 Rated IP rating stands for 'Ingress Protection rating' and this helps us determine what bathroom electricals can go in particular bathroom zones. An IP (Ingress Protection) number.