How to read NFPA 70E approach boundaries

Three lines around every exposed energized part

Look up Tables 130.4(E)(a) and (b) in the free NFPA viewer. NFPA offers read-only access to the current edition of NFPA 70E at no cost. This page explains how to use the tables; it does not reproduce them.

Picture circles drawn around an exposed energized part. The limited approach boundary is the outer shock line — inside it, a person could get close enough to contact something energized. The restricted approach boundary is the inner shock line, where accidental movement could put a body part or tool in contact. Both distances come from the voltage tables, with separate tables for AC and DC. The limited approach boundary has two columns: a large distance for movable conductors (overhead lines, conductors that can sway) and a smaller one for fixed circuit parts like bus and terminals.

The arc flash boundary is a different animal: it is the distance at which the incident energy from an arc drops to the level that causes a second-degree burn on bare skin. It depends on available fault current and clearing time, not just voltage, so it comes from the equipment label (incident energy analysis) or from the PPE category method. See our guide to NFPA 70E PPE categories for how that works.

Worked example. A qualified electrician is troubleshooting a 480Y/277 V panel with the dead front off. Enter the AC table at 480 V (the system voltage, not 277 V). The limited approach boundary to the fixed bus is 3 ft 6 in and the restricted approach boundary is 1 ft 0 in. The arc flash boundary comes off the panel’s label. The helper stays outside the larger of the two unless escorted — and never crosses the restricted line.

Qualified vs unqualified. A qualified person has the training to recognize and avoid the hazards of that specific equipment and task — it is task-specific, not a job title. Put the boundaries, the energized work permit, and the job briefing on your electrical JSA template. For overhead lines near cranes and equipment, the OSHA rules apply too — see the crane power line clearance chart. Field PM keeps JSAs, permits, and toolbox talks with the job so the record is there when it is needed.