1910.306(k)(4): Portable Distribution and Termination Boxes
Employers may only use portable distribution and termination boxes that meet set requirements. Boxes must have no live parts exposed to accidental contact, outdoor boxes must be weatherproof with the bottom at least 152 mm (6 in.) above the ground, busbars and receptacle overcurrent protection must be properly rated, and single-pole connectors must meet locking and interlocking rules.
Key takeaways
- 1910.306(k)(4) is part of OSHA's general industry standards (29 CFR Part 1910, Subpart S).
- OSHA cited it 1 times in the last 3 years, in 1 inspections, with $2,800 in current penalties.
- 1 death is linked to inspections that cited this rule.
- Related part: 1910.306(k) Carnivals, circuses, fairs, and similar events (2 citations).
- Free 5-minute toolbox talk for your crew below.
In this article
What this rule covers
29 CFR 1910.306(k)(4) ("Portable distribution and termination boxes") is one requirement inside 1910.306 Specific purpose equipment and installations, an OSHA general industry standard (Part 1910, Subpart S). It includes 11 sub-paragraphs. The official text below is copied word for word from the Electronic Code of Federal Regulations (eCFR). The numbers, injury cases and training on this page show how OSHA enforces it on real job sites.
Official text
(4) Portable distribution and termination boxes. Employers may only use portable distribution and termination boxes that meet the following requirements: 1 citations
(i) Boxes shall be designed so that no live parts are exposed to accidental contact. Where installed outdoors, the box shall be of weatherproof construction and mounted so that the bottom of the enclosure is not less than 152 mm (6 in.) above the ground;
(ii) Busbars shall have an ampere rating not less than the overcurrent device supplying the feeder supplying the box. Busbar connectors shall be provided where conductors terminate directly on busbars;
(iii) Receptacles shall have overcurrent protection installed within the box. The overcurrent protection may not exceed the ampere rating of the receptacle, except as permitted in § 1910.305(j)(4) for motor loads;
(iv) Where single-pole connectors are used, they shall comply with the following:
(A) Where ac single-pole portable cable connectors are used, they shall be listed and of the locking type. Where paralleled sets of current-carrying single-pole separable connectors are provided as input devices, they shall be prominently labeled with a warning indicating the presence of internal parallel connections. The use of single-pole separable connectors shall comply with at least one of the following conditions:
(1) Connection and disconnection of connectors are only possible where the supply connectors are interlocked to the source and it is not possible to connect or disconnect connectors when the supply is energized; or
(2) Line connectors are of the listed sequential-interlocking type so that load connectors are connected in the following sequence:
(i) Equipment grounding conductor connection;
(ii) Grounded circuit-conductor connection, if provided; and
(iii) Ungrounded conductor connection; and so that disconnection is in the reverse order; or
(3) A caution notice is provided adjacent to the line connectors indicating that plug connection must be in the following sequence:
(i) Equipment grounding conductor connection;
(ii) Grounded circuit-conductor connection, if provided; and
(iii) Ungrounded conductor connection; and indicating that disconnection is in the reverse order; and
(B) Single-pole separable connectors used in portable professional motion picture and television equipment may be interchangeable for ac or dc use or for different current ratings on the same premises only if they are listed for ac/dc use and marked to identify the system to which they are connected;
(v) Overcurrent protection of equipment and conductors shall be provided; and
(vi) The following equipment connected to the same source shall be bonded: Open (k)(4)(vi) 1 citations
(A) Metal raceways and metal sheathed cable;
(B) Metal enclosures of electrical equipment; and
(C) Metal frames and metal parts of rides, concessions, trailers, trucks, or other equipment that contain or support electrical equipment. Open (k)(4)(vi)(c) 1 citations
Source: eCFR, text current as of 2026-10-15. Read all of 1910.306.
Injuries linked to this rule
1 death is linked to inspections where OSHA cited 1910.306(k)(4).
At 11:18 p.m. on July 6, 2024, Employee #1 was leaning against a structural truss that secured one corner of a vinyl canopy over the customer waiting area while talking to coworkers. The structural truss became energized, and Employee #1 received a fatal electrical shock.…
Where and how often it was cited
Free toolbox talk
A 5-minute crew talk on 1910.306(k)(4), plus alerts when this rule changes. Free.
OSHA interpretation letters
None exist. OSHA has not published a letter of interpretation for 1910.306(k)(4).
Related parts of this rule
- 1910.306(k) Carnivals, circuses, fairs, and similar events 2 citations
- 1910.306(k)(4)(vi) 1 citations
- 1910.306(k)(4)(vi)(C) 1 citations
Get your crew competent
Trainers on Black Belt Safety: Marc Harvey, Dana Reyes
Trainers and suppliers: feature your business on this rule for $25/month.
Frequently asked questions
How high must an outdoor box be mounted?
So the bottom of the enclosure is not less than 152 mm (6 in.) above the ground.
Can live parts be exposed?
No, boxes must be designed so no live parts are exposed to accidental contact.
What rules apply to ac single-pole portable cable connectors?
They must be listed and of the locking type.
About this page
Sources
- 29 CFR 1910.306 (eCFR), text current as of 2026-10-15
- U.S. Department of Labor enforcement data: OSHA inspections, citations and accident records, copied nightly; data as of 2026-10-20
3-year window. Federal OSHA only; state-plan rules are not counted. Plain-language text is a summary, not legal advice; the official text controls. Black Belt Safety is not part of OSHA or the Department of Labor.