BS IEC 62990-1:2019 pdf download.Workplace atmospheres
4.2.1 General
For Type HM equipment the upper limit of measurement shall be equal to or greater than 2 times the reference value. (See Table A.1.) The requirement for the lower limit of measurement is in 6.4.2.
The equipment shall be constructed in such a manner that regular functional checks can be easily undertaken by the user and that it can be equipped with suitable devices for application of test gas (field calibration kit).
Toxic gas detection equipment or parts thereof (e.g. remote sensors) shall be constructed of materials known to be resistant to degradation by the environment in which they are intended to be used. Equipment specifically intended for use in the presence of corrosive vapours or gases, or which can produce corrosive by-products as a result of the detection process (e.g. catalytic oxidation or other chemical process) shall be constructed of materials known to be resistant to corrosion by such substances.
Materials and components used in the construction of the equipment which are relevant to performance of the equipment shall be used within the material and component manufacturer's ratings or limitations unless otherwise specified by appropriate safety standards. If such material and component ratings are not available, demonstrated functionality of the equipment may be used. All materials along the gas path shall not cause an inaccurate reading due to adsorption and absorption effects of materials in contact with the toxic gas.
For aspirated equipment, inlet and outlet ports shall be unambiguously marked to ensure the correct connection of any sample and exhaust lines.
Any failure of functions of the gas detection equipment not relevant to safety or health shall not adversely affect the functions of the equipment related to safety.
EXAMPLE: Equipment with 4 to 20 mA and Highway Addressable Remote Transducer (HART) Protocol communication where HART communication is defined in the instruction manual as not related to salety. The loss of HART communication is not related to safety.
4.2.2.1 Indicators
Readily distinguishable indicators shall be provided to show that the equipment is energized,in alarm or in a special state.
Portable equipment shall provide visual and audible indicators for both fault and alarm states.The special state“warm-up" shall be indicated by a visual and/or audible signal. The special states“calibration mode" and "parameterization mode" shall be indicated by a visual signal.
Transportable or fixed equipment shall provide visual indicators for power, special states and alarm states. It is permitted for fixed equipment that the indications related to gas detection transmitters and remote sensors are shown only at the (separate) gas detection control unit.BS IEC 62990-1 pdf download.