30 CFR § 57.4000 - Definitions.

---
identifier: "/us/cfr/t30/s57.4000"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "30 CFR § 57.4000 - Definitions."
title_number: 30
title_name: "Mineral Resources"
section_number: "57.4000"
section_name: "Definitions."
chapter_name: "MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR"
subchapter_number: "K"
subchapter_name: "METAL AND NONMETAL MINE SAFETY AND HEALTH"
part_number: "57"
part_name: "SAFETY AND HEALTH STANDARDS—UNDERGROUND METAL AND NONMETAL MINES"
positive_law: false
currency: "2026-03-24"
last_updated: "2026-03-24"
format_version: "1.1.0"
generator: "[email protected]"
authority: "30 U.S.C. 811."
regulatory_source: "50 FR 4082, Jan. 29, 1985, unless otherwise noted."
cfr_part: "57"
---


# 57.4000 Definitions.

The following definitions apply in this subpart.

*Combustible liquids.* Liquids having a flash point at or above 100 °F (37.8 °C). They are divided into the following classes:

Class II liquids—those having flash points at or above 100 °F (37.8 °C) and below 140 °F (60 °C).

Class IIIA liquids—those having flash points at or above 140 °F (60 °C) and below 200 °F (93.4 °C).

Class IIIB liquids—those having flash points at or above 200 °F (93.4 °C).

*Escapeway.* A designated passageway by which persons can leave an underground mine.

*Flash point.* The minimum temperature at which sufficient vapor is released by a liquid to form a flammable vapor-air mixture near the surface of the liquid.

*Main fan.* A fan that controls the entire airflow of an underground mine or the airflow of one of the major air circuits of the mine.

*Mine opening.* Any opening or entrance from the surface into an underground mine.

*Safety can.* A container of not over five gallons capacity that is designed to safely relieve internal pressure when exposed to heat and has a spring-closing lid and spout cover.

[50 FR 4082, Jan. 29, 1985, as amended at 68 FR 32361, May 30, 2003; 69 FR 38842, June 29, 2004]