AS NZS 4641:2018 pdf free.Electrical equipment for detection of oxygen and other gases and vapours at toxic levels- General requirements and test methods.
1.3 DEFINITIONS
For the purpose of this Standard the definitions below apply.
NOTE: For other definitions, AS/NZS 60079.0 and AS/NZS 60079.29.1 may be taken for guidance.
1.3.1 Gas properties
1.3.1.1 Ambient temperature
Temperature of the normal atmosphere surrounding the equipment.
1.3.1.2 Clean air
Air that is free of flammable or toxic gases, and interfering or contaminating substances.
1 .3.1.3 Concentration
The amount of the gas or vapour of interest in a specified amount of the background gas or air, expressed in suitable units.
NOTE: Typical units include volume fraction (v/v) (see Clause 1.3.1.14); molar (moles per mole — rn/rn); percentage of the lower flammable limit (LFL) of a particular substance; parts per million by volume (ppm); parts per billion by volume (ppb).
1.3.1.4 Explosive gas atmosphere
Mixture of flammable gases or vapours, with air, which after ignition in normal atmospheric conditions, permits self-sustaining flame propagation.
NOTES:
I This definition specifically excludes dusts and fibres in suspension in air. Mists are not covered by this Standard.
2 Although a mixture that has concentration above upper flammable limit is not an explosive atmosphere, in certain cases it is advisable to consider it as an explosive gas atmosphere.
3 Normal atmospheric conditions include variations above and below the reference levels of
101.3 kPa and 20°C provided that the variations have a negligible effect on the explosive properties of the flammable materials.
1.3.1.5 Flammable gas
Gas or vapour which, when mixed with air in a certain proportion, will form an explosive atmosphere.
NOTE: For the purpose of this Standard the term ‘flammable gas’ includes flammable vapours.
1.3.1.6 Functional check
Application of test gas to the monitor to check the response signal or the generation of an
alarm, without adjustments of zero, sensitivity, or alarm level.
1 .3. 1.7 Lower flammable limit (LFL)
Volume fraction of flammable gas or vapour in air below which an explosive gas atmosphere does not form, expressed as a percentage (refer to AS/NZS 60079.20.1).
NOTE: This is also known as lower explosive limit (LEL).AS NZS 4641 pdf download.