Do you know where to install intrinsically safe equipment?
Where can you install intrinsically safe equipment? Suppose you bought intrinsically safe equipment for a Class II, Division 1 location. That project turned out so well that you want to buy more of that same equipment for use in a Class I, Division 2 location. Is anything stopping you?
Probably not. Most likely, that equipment is identified for use in both locations. However, it might not be so identified. You’ll need to check that. Make sure any intrinsically safe equipment is identified for the hazardous location in which you intend to use it [504.10(B)].
Do you also need an intrinsically safe enclosure for your intrinsically safe I/O modules (and wiring, etc.)? No, you can use a general-purpose enclosure [504.10(C)]. Because all the apparatus is incapable of igniting a flammable gas or vapor, further protection (via enclosure) is unnecessary.
However, make sure you properly bond that enclosure. For example, don’t rely on a concentric knockout for a bonding connection. And don’t try to make a connection through paint; that will introduce a resistance and thus create differences in potential.