Flow control devices for convector heaters are provided. Such devices may include a casing in the shape of a cylindrical tube having in a first portion thereof, facing in a mounted condition towards the intake conduit of a convector heater, a plurality of first openings and in a second portion thereof, facing in the mounted condition towards the opposite side of the intake conduit, a plurality of second openings, the casing being arranged to be mounted onto the ceiling (S) in such a manner that the first and second openings allow the inside of the casing to be placed into communication with a first space (A1) beneath the ceiling (S) and with a second space (A2) above the ceiling (S), respectively; a closure member in the shape of a cylindrical tube which is mounted within the casing and is axially slidable relative to the latter between a first position, in which it leaves the first openings open and closes the second openings, and a second position, in which it closes the first openings and leaves the second openings open; and actuation elements for controlling the axial sliding movement of the closure member relative to the casing between the first and second position.