Accessory for a fan

1. A combination of an external accessory and a portable fan, the portable fan comprising a base having an air inlet located in an external side wall of the base, the air inlet comprising an array of apertures extending about the base, and a nozzle detachably connectable to the base, the nozzle comprising an annular inner casing section, an outer casing extending about the inner casing section, an interior passage located between the inner casing section and the outer casing section for receiving a primary air flow from the base, and a mouth for emitting the primary air flow, the inner casing section defining an opening extending through the nozzle and through which a secondary air flow from outside the fan is drawn by the primary air flow emitted from the mouth, the accessory comprising a high energy particle arrester filter and at least one connector for detachably connecting the accessory to the fan through rotation of the accessory relative to the base, the external accessory being in the form of a sleeve locatable about the external side wall of the base so that the filter is located upstream from the air inlet of the fan, wherein said at least one connector comprises a first connector for connecting the accessory to the base, and a second connector for connecting the accessory to the nozzle, wherein the nozzle comprises a connector for connecting the nozzle to the base, and wherein the first connector for connecting the accessory to the base is substantially the same as the connector for connecting the nozzle to the base.

2. The combination of claim 1 , wherein the accessory comprises at least one seal for engaging an outer surface of the fan.

3. The combination of claim 1 , wherein the accessory comprises two annular discs between which the filter is located.

4. The combination of claim 3 , wherein each disc comprises a raised rim extending towards the other disc for retaining the filter between the discs.

5. The combination of claim 3 , wherein the filter is adhered to the discs.

6. The combination of claim 1 , wherein the accessory comprises an outer cover extending about the filter, the cover comprising a plurality of apertures.

7. The combination of claim 1 , wherein the base is substantially cylindrical in shape.

8. The combination of claim 1 , wherein the base houses a system for generating the primary air flow.

9. The combination of claim 8 , wherein the system for generating the primary air flow is arranged to generate an air flow having a static pressure of at least 150 Pa.

10. The combination of claim 8 , wherein the system for generating the primary air flow is arranged to generate an air flow having a static pressure in the range from 250 to 1 kPa.

11. The combination of claim 1 , wherein the accessory is attachable to the portable fan between the base and the nozzle.

12. The combination of claim 11 , wherein the accessory comprises a first seal for engaging the base of the fan, and a second seal for engaging the nozzle of the fan.

13. The combination of claim 1 , wherein the base comprises a connector for connecting the base to the nozzle, and the second connector for connecting the accessory to the nozzle is substantially the same as the connector for connecting the base to the nozzle.

14. The combination of claim 1 , wherein the fan is one of a desk fan, a tower fan and a pedestal fan.

15. A combination of an external accessory and a portable fan, the portable fan comprising a base having an air inlet located in an external side wall of the base, the air inlet comprising an array of apertures extending about the base, and a nozzle detachably connectable to the base, the nozzle comprising an annular inner casing section, an outer casing extending about the inner casing section, an interior passage located between the inner casing section and the outer casing section for receiving a primary air flow from the base, and a mouth for emitting the primary air flow, the inner casing section defining an opening extending through the nozzle and through which a secondary air flow from outside the fan is drawn by the primary air flow emitted from the mouth, the accessory comprising a high energy particle arrester filter and at least one connector for detachably connecting the accessory to the fan through rotation of the accessory relative to the base, the external accessory being in the form of a sleeve locatable about the external side wall of the base so that the filter is located upstream from the air inlet of the fan, wherein said at least one connector comprises a first connector for connecting the accessory to the base, and a second connector for connecting the accessory to the nozzle, wherein the base comprises a connector for connecting the base to the nozzle, and wherein the second connector for connecting the accessory to the nozzle is substantially the same as the connector for connecting the base to the nozzle.