Safety, Codes, and Standards
What the exam tests
Safety and code questions mix regulation recall with field judgment. Know the OSHA basics: 29 CFR 1910.147 lockout/tagout (identify all energy sources, notify, shut down, isolate, apply lock and tag, release stored energy, verify by test), 1910.146 permit-required confined spaces, and the hot work permit system. NFPA 70 (NEC) Articles 500-505 cover hazardous locations: Class I gas/vapor, Class II dust, Class III fibers; Division 1 vs. Division 2 for normal vs. abnormal release; and the Zone system 0/1/2 for gas and 20/21/22 for dust. Zone 0 has no Division equivalent, and Division 1 roughly matches Zone 1. Protection techniques include explosion-proof enclosures with conduit seals, purged and pressurized systems, and intrinsic safety, which relies on entity parameters (Voc, Isc, Ca, La) matched across barrier, field wiring, and field device. NFPA 70E governs arc flash and energized work permits.
Traps
Explosion-proof does not mean safe to open while energized. Intrinsically safe equipment must be approved as a system, not as individual parts. Verification of zero energy is done with a meter rated for the circuit, not by pressing the start button. Expect questions on SDS access, PPE selection, and ISA-5.1 symbol identification.
Rule of thumb
Use the live-dead-live check: prove the meter on a known live source, test the de-energized conductor, then prove the meter again.
Worked example
A transmitter in a Class I, Division 2 area is replaced. The replacement must be listed for the same class and division (or the area zone), and the conduit seal and any IS barrier must be reinstalled exactly as before.