Abstract: A respirator has a filter that is located in an air duct. A blower has an air conduction housing and an impeller wheel located in said air conduction housing, with an impeller wheel that is rotationally mounted inside said housing. The blower is controlled by a sensor. The output of the blower is controlled by means of an electronic control circuit. The sensor is a volume flow or mass flow sensor located in the air duct, and is independent of the blower and controls the blower by means of the control circuit so that the flow of respiratory air remains essentially constant.

Abstract: A machine frame with two side members at its ends comprises support arms, which are pivotably mounted in semi-circular cut-out bearing supports. The bearing supports may be arranged on differently high pedestals, which may result in different inclined positions for the machine frame with respect to a machine room floor. The inclined position may provide for a variable looping angle .beta. at the drive pulley and variable cable spacing between the cage cables and the counterweight cables. Furthermore, the deflecting roller may be mounted in laterally displaceable bearing plates. The deflecting roller may be inserted above or below a pair of side members. The position of the deflecting roller with respect to the side members may also have an effect on the looping angle .beta. and the cable spacing. The combination of these adjustment possibilities enables the substantially universally adaptability of the machine frame to different elevator systems and applications.