Abstract: An air flow regulating apparatus comprising a regulator housing having an air inlet and an air outlet and an air passage extending from the inlet to the outlet. In the passage there is provided at least one movable damper blade attached to a shaft extending transversely to the flow direction in the air passage and having its ends pivotally journalled in the air passage side walls. One of the shaft ends extends through an opening in one of said side walls and has the form of a counterweight neck on the outside of the housing, there being attached to said neck an adjustable mass body system. The damper blade is angular in cross section and has a plane forward blade portion and a plane rear blade portion enclosing an obtuse angle with said forward blade portion.