The present document describes a wind box used in the air supply of a chemical recovery furnace, the wind box comprising a frame (1) having at least one air inlet opening (2) and at least one air supply opening (3) through which air is led from an air channel via the wind box to the recovery furnace. The wind box further comprises at least one combined actuator (25) for regulating the air flow through the wind box and for cleaning each air supply opening (3) as well as means (19, 21) for moving each actuator (25). The invention is based on using a cleaning head (15) smaller than the air supply opening (3) when cleaning the air supply opening (3), whereby its path instead of a longitudinal motion is determined to be curved such that one to and from motion of the cleaning head will rub of all deposit from both the upper and the lower edge of the air supply opening (3) and also from the area between these.