Abstract: A monitor is disclosed for monitoring an atmosphere for the presence of a target gas. The monitor includes an electrical gas sensor having a working (sensing) electrode and a counter electrode, an operational amplifier connected between the sensor electrodes, a detector, and a circuit. The sensor provides a current between the electrodes that is indicative of the amount of a target gas in the atmosphere. The operational amplifier generates an output signal according to the current flowing between the terminals where the output signal is indicative of the amount of target gas in the atmosphere. The detector detects when the current flowing between the sensor electrodes exceeds a predetermined threshold. The circuit restricts the potential difference between the sensor electrodes when the current between the terminals exceeds the predetermined threshold by supplying additional current or removing current from the working sensor electrode.

Abstract: A portable detector is described for monitoring a gas in an atmosphere. The detector comprises a housing, at least one gas sensor carried by the housing, and electrical connectors carried by the housing for establishing electrical connections to a calibration apparatus and a microprocessor carried by the housing. The microprocessor controls the calibration apparatus via signals provided to microprocessor through the connectors to initiate the supply of calibration gas to the detector at a predetermined rate.

Abstract: A single-piece adapter (10) is disclosed for supplying gas to a gas detector (32) that contains at least one gas sensor (34) and that has a gas inlet (30) for allowing gas at the inlet to come into contact with the at least one sensor (34), which adapter comprises: a chamber (24) having an opening formed by a rim (22) for fitting over the gas inlet of a gas detector (32), the chamber having an inner surface (18), an inlet duct (14) for feeding gas into the chamber in a direction transverse to the opening, and an outlet (16) to vent gases from within the chamber. The inner surface (18) of the chamber is formed by a first moulding (12) of a rigid, non-absorbent material and a second moulding (20) of resilient material. The second moulding forms the rim (22) for providing a gas-tight seal between the adapter (10) and the detector (32).

Abstract: An apparatus is described for calibrating at least one sensor within a gas detector (22), which detector has a gas inlet in fluid communication with the or each sensor, the apparatus comprising a housing (10) that contains: a) a surface (24) for abutting against the detector (22); b) a holder (14) for holding the gas detector (22) with respect to the housing (10) in such a manner that a region of the detector containing the gas inlet abuts against the surface (24) of the housing to form a sealed gas interface between the surface (24) and the detector (22); c) a connector for connecting a source of pressurised calibration gas (12) to the apparatus, d) a conduit (32) for delivering a calibration gas from the connector (34) to the interface between the detector and the apparatus housing, e) electrical connections (40) within the holder for forming electrical connections between the apparatus and a detector held within the holder, and e) a flow controller (34, 36) within the conduit for providing calibration gas