A protection or communication device like thermal relay or zener barriere installed outside of Ex but wired to an Ex device how you do marking there?
In case of ATEX and wired to Zone 1 but installation located outside of Ex the correct marking is II(2)G.
Note: Parentheses indicate that a safety device can be used to protect products with equipment categories 2 and 3, but the safety device itself and the connected Ex asset where it is integrated must be installed in a safe area.
What about IECEx? Is there any other option? Any national deviation?
Note: few more there are, E.g see ECASEX in UAE.
Keep up good work!