A fan assembly includes a motor-driven impeller for creating an air flow, at least one heater for heating a first portion of the air flow, and a casing comprising at least one air outlet for emitting the first portion of the air flow, and first channel for conveying the first portion of the air flow to the at least one air outlet. To cool part of the casing, the casing diverts a second portion of the air flow away from the at least one heater, and comprises a second channel for conveying the second portion of the air flow along an internal surface of the casing. This second portion of the air flow may merge with the first portion within the casing, or it may be emitted through at least one second air outlet of the casing.