30 CFR § 56.6406 - Duration of current flow.

---
identifier: "/us/cfr/t30/s56.6406"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "30 CFR § 56.6406 - Duration of current flow."
title_number: 30
title_name: "Mineral Resources"
section_number: "56.6406"
section_name: "Duration of current flow."
chapter_name: "MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR"
subchapter_number: "K"
subchapter_name: "METAL AND NONMETAL MINE SAFETY AND HEALTH"
part_number: "56"
part_name: "SAFETY AND HEALTH STANDARDS—SURFACE METAL AND NONMETAL MINES"
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. 811."
regulatory_source: "50 FR 4054, Jan. 29, 1985, unless otherwise noted."
cfr_part: "56"
---


# 56.6406 Duration of current flow.

If any part of a blast is connected in parallel and is to be initiated from powerlines or lighting circuits, the time of current flow shall be limited to a maximum of 25 milliseconds. This can be accomplished by incorporating an arcing control device in the blasting circuit or by interrupting the circuit with an explosive device attached to one or both lead lines and initiated by a 25-millisecond delay electric detonator.