Abstract: A ventilation appliance for rooms having a box-like housing which can be used either as a ventilator with a radial fan or a pressure differential ventilator without such a fan. The configuration of the applicance insures a good sound damping action even when only short flow path are available in the housing or when, for functional reasons, the housing cannot be lined with sound damping material. For this purpose and enveloping spiral 21 for the blower wheel of the radial fan is formed directly from a block-like insert body of sound damping material such a plastic foam or foam rubber, the enveloping spiral having formed thereon an approximately tangential and/or radially connecting air connecting conduit. A replaceable filter for such a ventilation device is disclosed. A possible explanation is indicated for an unexpectedly effective mixing of entering air with room air upon installation of such a ventilating appliance.

Abstract: Safety control unit using a self-starting single-phase synchronous a.c. motor with a register closure.

Abstract: Ventilating device for rooms having air passage apertures and closure means movable by an electric drive between an open position and a closed position, a noxious gas sensor and electrical control means responsive to the gas sensor for operating the electric drive so that the closure means is moved to the open position when the gas sensor senses noxious gas concentration in the room above a predetermined level.

Abstract: Sound-absorbing air vent for rooms having openings that are selectively opened or closed by an electrical motor which is controlled by a sound-sensitive element.

Abstract: Air vent consisting of a fixed, gridlike apertured front panel and a stop plate disposed behind it, which plate is movable by a control mechanism in the direction of its plane and to the plane of the front panel and which plate in a position resting against the back of the front panel closes the grid apertures, but which in a separated position opens the grid apertures of the front panel for the passage of air.

Abstract: An air vent having a detachable front plate provided with apertures, a closure plate behind the front plate, an operating device for moving the closure plate toward and away from the front plate for blocking and unblocking and apertures, the operating device being connected to the closure plate by means of a slot and pin connection which allows the closure plate to be removed independently of the operating means.

Abstract: Baffle formed with a plurality of molded elastomeric plates within a housing for lining the interior of sound-absorbing ventilators, each plate having a central aperture and grooves in the broad sides of the plates which extend from the aperture to the edge of the plate; the apertures form a channel when the plates are stacked within the housing and the grooves form canals from the channel to the outside of the stacked plates.