Limited & Restricted Approach Boundaries

Two boundaries, one hazard

Both approach boundaries protect against shock. They exist because the risk of electric shock does not begin at the moment of contact — it begins at the distance where contact, or an arc jumping the gap, becomes credible.

The two boundaries mark two different levels of that risk, and the practical difference between them is not distance. It is permission: who is allowed to be there, and under what conditions.

The limited approach boundary

The limited approach boundary is the distance from an exposed energized conductor or circuit part within which a shock hazard exists.

It is the outer line, and it is the line that matters most for people who are not electrical workers. An unqualified person may not cross it while the parts are energized and exposed. Anyone working inside it must be a qualified person, and qualification here is specific: a person working within the limited approach boundary must additionally be trained to distinguish exposed energized parts from other equipment, to determine the nominal voltage of those parts, to know the approach distances that correspond to that voltage, and to make the decisions that job planning, hazard identification, risk assessment and PPE selection require.

The restricted approach boundary

The restricted approach boundary sits closer in. It marks the distance within which there is an increased likelihood of shock caused by arc-over, combined with inadvertent movement — a hand drifting, a tool slipping, a body shifting balance in a cramped space.

Crossing it raises the bar again. Work inside the restricted approach boundary is one of the conditions that requires a documented energized electrical work permit. Insulated tools are required within this boundary, and under the 2027 edition also wherever an electrical contact hazard is present, even outside it.

How these differ from the arc flash boundary

This is the most common point of confusion, and it is worth being precise about.

• Approach boundaries guard against shock. They come from a table, keyed to system voltage, and they govern who may approach.
• The arc flash boundary guards against thermal energy. It is the distance at which incident energy equals 1.2 cal/cm², it is calculated for the specific equipment, and it governs what arc-rated protection is required.

The arc flash boundary tool covers the thermal side; this page covers the shock side.

They are independent numbers. On the same piece of equipment, the arc flash boundary may sit well outside the limited approach boundary, or well inside it. Neither one substitutes for the other, and a full shock risk assessment records both approach boundaries alongside the voltage exposure and the required PPE.

Approach distances for AC systems

The distances are not calculated per installation the way an arc flash boundary is. They are read from a table in NFPA 70E — Table 130.4(E)(a) for AC systems — against the nominal system voltage. The values below cover exposed fixed circuit parts on AC systems through 36 kV.

Nominal system voltage (AC)	Limited approach boundary	Restricted approach boundary
50 V – 150 V	3 ft 6 in	Avoid contact
151 V – 750 V	3 ft 6 in	1 ft 0 in
751 V – 5 kV	3 ft 6 in	2 ft 1 in
5.1 kV – 15 kV	5 ft 0 in	2 ft 2 in
15.1 kV – 36 kV	6 ft 0 in	2 ft 7 in

Two notes that are easy to miss. The 50–150 V row applies to line-to-ground voltages up to 240 V, so a common 120/240 V single-phase service falls in that first row rather than the second. And above 900 m (3,000 ft), the restricted approach boundary needs a correction, because air is a weaker insulator at altitude — the standard points to references for those correction factors rather than printing corrected distances in the table itself.

Systems above 36 kV, and DC systems — which use a separate table, 130.4(E)(b) — are outside the scope of this page.

Fixed parts vs. movable conductors

The table distinguishes exposed fixed circuit parts from exposed movable conductors, and the difference is substantial. For movable conductors, the limited approach boundary is 10 ft 0 in at every voltage through 36 kV.

The reasoning is straightforward once stated: a fixed busbar stays where it is, while an overhead line or a suspended conductor can swing, sag or be displaced. The boundary accounts for the conductor moving toward the worker, not just the worker moving toward the conductor.

The boundary that no longer exists

Older training material, older labels and a great deal of internet content still refer to a prohibited approach boundary as though it were current. It is not. It was removed in the 2015 edition, and there are only two shock approach boundaries today: limited and restricted.

This matters more than a terminology quibble. If a written safety program, a work permit form or a training deck still lists three approach boundaries, that document has not been reviewed against the standard in over a decade — which usually means other things in it are stale too.

This guide is reference material on the shock approach boundaries in NFPA 70E. Distances are from Table 130.4(E)(a) of the standard; consult the current edition for the complete table, including systems above 36 kV and DC systems. Back to the NFPA 70E guide

Getting a team current on the 2027 edition? Live, instructor-led NFPA 70E classes run every week. See the schedule.