What are the requirements for intrinsically safe instrumentation?

Intrinsically safe (IS) systems limit energy to below ignition thresholds in hazardous areas. Requirements include: certified IS barriers/isolators (limit voltage, current, power), IS-rated devices (certified under IECEx, ATEX, FM, CSA), proper wiring (blue cables, separation from non-IS), grounding per entity parameters, documentation of entity parameter calculations (Voc, Isc, Ca, La vs device requirements), and installation per area classification (Zone 0/1/2 or Division 1/2). Entity concept requires checking voltage/current limits and cable capacitance/inductance. Barrier types: Zener (simple, requires good ground) and galvanic isolators (no special ground required).