Abstract: A system for redundantly detecting a gas is provided. The system includes first and second series-connected gas sensors and a signaling module. If both gas sensors are functioning normally, the signaling module provides an alert when both gas sensors detect a predetermined gas concentration. If however any one of the gas sensors is experiencing a fault condition, the faulty gas sensor's alarm is shunted by operation of a fault relay, and the signaling module provides an alert when the non-faulty gas sensor detects a predetermined gas concentration. If both gas sensors are experiencing a fault condition, both gas sensors' alarms are shunted by fault relays, and an audible and/or visual alert is generated by the signaling module. Embodiments of the present invention are well suited for industrial facilities, manufacturing facilities, research and development laboratories, and other locations where unsafe gas concentrations may become present.

Abstract: A generator rotor part for carrying at least one row of blower blades, each blade having a blade root. The rotor part has the form of a cylinder having a longitudinal axis and composed of at least one first portion having a first outer diameter and at least one second portion axially spaced from, and adjacent to, the first portion, the second portion having a second outer diameter which is less than the first diameter so that the first portion protrudes radially outwardly of the second portion and has a radially extending surface constituting a boundary between the first and second portions. The first portion is provided with a plurality of slots each extending from the radially extending surface and at a given angle of less than 90.degree. relative to the longitudinal axis of the rotor part for receiving and holding the root of a respective blower blade.