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ANSI/ISA 12.21.02-2013
Explosive Atmospheres - Part 28: Protection of equipment and transmission systems using optical radiation
This standard explains the potential ignition hazard from equipment using optical radiation intended for use in explosive gas and combustible dust atmospheres. It covers EPLs Ma, Mb, Ga, Gb, Gc, Da, Db and Dc. It also covers equipment, which itself is located outside but its emitted optical radiation enters such atmospheres. It describes precautions and requirements to be taken when using optical radiation transmitting equipment in explosive gas and combustible dust atmospheres. It also outlines a test method, which can be used to verify a beam is not ignition capable under selected test conditions, if the optical limit values cannot be guaranteed by assessment or beam strength measurement.
The International Society of Automation [isa]