The fan unit includes a tubular collecting wall mounted on the circuit-mounting frame and disposed above the carrier
. The tubular collecting wall has upper and lower wall portions. The upper wall portion has a front side formed with a radial air flow outlet that is registered with the air outlet of the front housing part. The lower wall portion has a fan device mounted therein and connected electrically to the control circuit. Aromatherapy diffuser is controlled by the control circuit so as to be adapted to draw aroma of the aromatic preparation on the carrier into the tubular collecting wall and so as to be adapted to blow the aroma inside the tubular collecting wall out of the air outlet of the housing via the radial air flow outlet of the tubular collecting wall.