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Why is light blue for intrinsically safe ? Where does it come from ?
It comes from IEC 60079-11 Explosive atmospheres - Part 11: Equipment protection by intrinsic safety "i"
IEC 60079-11 (https://webstore.iec.ch/publication/626)
12.2 Marking of connection facilities
Connection facilities, terminal boxes, plugs and sockets of intrinsically safe apparatus and associated apparatus shall be clearly marked and shall be clearly identifiable. Where a colour is used for this purpose, it shall be light blue.
Where parts of an apparatus or different pieces of apparatus are interconnected using plugs and sockets, these plugs and sockets shall be identified as containing only intrinsically safecircuits. Where a colour is used for this purpose, it shall be light blue.
In addition, sufficient and adequate marking shall be provided to ensure correct connection for Mthe continued intrinsic safety of the whole. NOTE It may he necessary to include additional labels, for example on or adjacent to plugs and sockets, toachieve this If clarity of Intention is maintained, the apparatus label may suffice.
Virgolino De Freitas