30 CFR § 18.42 - Explosion-proof distribution boxes.

---
identifier: "/us/cfr/t30/s18.42"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "30 CFR § 18.42 - Explosion-proof distribution boxes."
title_number: 30
title_name: "Mineral Resources"
section_number: "18.42"
section_name: "Explosion-proof distribution boxes."
chapter_name: "MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR"
subchapter_number: "B"
subchapter_name: "TESTING, EVALUATION, AND APPROVAL OF MINING PRODUCTS"
part_number: "18"
part_name: "ELECTRIC MOTOR-DRIVEN MINE EQUIPMENT AND ACCESSORIES"
positive_law: false
currency: "2026-04-05"
last_updated: "2026-04-05"
format_version: "1.1.0"
generator: "[email protected]"
authority: "30 U.S.C. 957, 961."
regulatory_source: "33 FR 4660, Mar. 19, 1968, unless otherwise noted."
cfr_part: "18"
---


# 18.42 Explosion-proof distribution boxes.

(a) A cable passing through an outside wall(s) of a distribution box shall be conducted either through a packing gland or an interlocked plug and receptacle.

(b) Short-circuit protection shall be provided for each branch circuit connected to a distribution box. The current-carrying capacity of the specified connector shall be compatible with the automatic circuit-interrupting device.

(c) Each branch receptacle shall be plainly and permanently marked to indicate its current-carrying capacity and each receptacle shall be such that it will accommodate only an appropriate plug.

(d) Provision shall be made to relieve mechanical strain on all connectors to distribution boxes.