30 CFR § 27.34 - Test for intrinsic safety.

---
identifier: "/us/cfr/t30/s27.34"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "30 CFR § 27.34 - Test for intrinsic safety."
title_number: 30
title_name: "Mineral Resources"
section_number: "27.34"
section_name: "Test for intrinsic safety."
chapter_name: "MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR"
subchapter_number: "B"
subchapter_name: "TESTING, EVALUATION, AND APPROVAL OF MINING PRODUCTS"
part_number: "27"
part_name: "METHANE-MONITORING SYSTEMS"
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: "31 FR 10607, Aug. 9, 1966, unless otherwise noted."
cfr_part: "27"
---


# 27.34 Test for intrinsic safety.

Assemblies, subassemblies, or components that are designed for intrinsic safety shall be tested by introducing into the circuit(s) thereof a circuit-interrupting device which produces an electric spark from the current in the circuit. The circuit-interrupting device shall be placed in a gallery containing various flammable natural gas-air mixtures. To meet the requirements of this test, the spark shall not ignite the flammable mixture. For this test the circuit-interrupting device shall be operated not less than 100 times at 125 percent of the normal operating voltage of the particular circuit.