Gas Detection Dictionary
aIt: Auto-Ignition Temperature.
Analogue/analog output: Standard mA output from a sensor or transmitter. Normally described as 4-20mA. The alternative is a mV bridge output from a catalytic type sensor.
Apparatus group: The classification of flammable gases into groups that are associated with required apparatus design standards.
Asphyxiation: Death resulting from lack of Oxygen.
ATEX: European Explosive Atmospheres Directives (ATmosphere EXplosives).
Baseefa: British Approvals Service for Electrical Equipment in Flammable Atmospheres – UK Safety Certification.
BMs: Building Management System.
Binary mixture of gas: A mixture of two gases only.
Breathing zone: 10 In/25cm radius from the nose and mouth.
Bridge circuit: Wheatstone Bridge circuit used in catalytic detector design.
CAS number: Chemical Abstracts Service. CAS registry number used to identify substances without the ambiguity of chemical nomenclature.
Calibration: The process of adjusting the output of the detector to give an accurate reading of gas concentration over its measuring range.
Catalytic sensor: For detection of combustible gases. These are made of an electrically heated Platinum wire coil, covered first with a ceramic base such as alumina and then with a final outer coating of Palladium or Rhodium catalyst dispersed in a substrate of Thoria.
CE: Indicates compliance to all relevant European directives.
Cell: An individual sensor.
Cenelec: Comité Européen de Normalisation Électrotechnique.
CESI: Centro Elettrotecnico Sperimentale Italiano – Italian Safety Certification.
Channel: One line or point of gas detection.
Conduit: Metal tubing mainly used in the US for installation of wires in hazardous areas.
COSHH: Control of Substances Hazardous to Health.
dBA: Decibels, relative to the A weighting scale (as affected by the human ear).
DCS: Distributed Control System.
Domestic: gas detector Gas detector designed specifically for use in domestic or residential properties.
Division: North American area classification of a hazardous area (Division 1 or 2) that defines the length of time a hazard is present.
Electrochemical cell sensor: Electrochemical sensors are essentially fuel cells composed of noble metal electrodes in an electrolyte.
Ex d: Hazardous Area Design Standard “Flameproof”.