30 CFR § 7.502 - Definitions.

---
identifier: "/us/cfr/t30/s7.502"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "30 CFR § 7.502 - Definitions."
title_number: 30
title_name: "Mineral Resources"
section_number: "7.502"
section_name: "Definitions."
chapter_name: "MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR"
subchapter_number: "B"
subchapter_name: "TESTING, EVALUATION, AND APPROVAL OF MINING PRODUCTS"
part_number: "7"
part_name: "TESTING BY APPLICANT OR THIRD PARTY"
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."
regulatory_source: "53 FR 23500, June 22, 1988, unless otherwise noted."
cfr_part: "7"
---


# 7.502 Definitions.

The following definitions apply in this subpart:

*Apparent temperature.* A measure of relative discomfort due to the combined effects of air movement, heat, and humidity on the human body.

*Breathable oxygen.* Oxygen that is at least 99 percent pure with no harmful contaminants.

*Flash fire.* A fire that rapidly spreads through a diffuse fuel, such as airborne coal dust or methane, without producing damaging pressure.

*Noncombustible material.* Material, such as concrete or steel, that will not ignite, burn, support combustion, or release flammable vapors when subjected to fire or heat.

*Overpressure.* The highest pressure over the background atmospheric pressure that could result from an explosion, which includes the impact of the pressure wave on an object.

*Refuge alternative.* A protected, secure space with an isolated atmosphere and integrated components that create a life-sustaining environment for persons trapped in an underground coal mine.