Abstract: A process is described for manufacturing gas diffusion electrodes, which process comprises: (a) treating an area of a pre-shrunk porous hydrophobic substrate so as to restrict the slurry deposited in step b) to the said area, preferably by forming a well in the area and/or treating the substrate in the area to render it less hydrophobic, e.g. by plasma treating the area; (b) dispensing a slurry of catalyst onto the said area, (c) removing liquid from the dispensed slurry, (d) treating the dried slurry to remove organic materials and e) cutting the catalyst and the underlying portion of substrate from the rest of the substrate.

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

Abstract: A method and apparatus for gas detection uses a sensor such as an electrochemical (EC) cell and includes a feedback control loop to control a pump to establish a first predetermined gas flow rate to the EC cell. The concentration of the gas at the first predetermined flow rate is measured. If the detected concentration exceeds a predetermined Alert value at the first flow rate an Initial Warning without remedial action is generated, and, the system then changes the gas flow rate before an Alarm is indicated. An Alarm is signaled only if the system verifies the first measurement. Preferably the first flow rate is set to optimize the measurement accuracy of the EC cell being used, and the second flow rate is lower than the first. Verification of an Alarm at the first flow rate may be conducted quickly by a quick-reaction process. The controller may periodically cycle the flow rates between the first and second rates for better accuracy and faster verification times.