42 CFR § 37.91 - Definitions.

---
identifier: "/us/cfr/t42/s37.91"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "42 CFR § 37.91 - Definitions."
title_number: 42
title_name: "Public Health"
section_number: "37.91"
section_name: "Definitions."
chapter_name: "PUBLIC HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES"
subchapter_number: "C"
subchapter_name: "MEDICAL CARE AND EXAMINATIONS"
part_number: "37"
part_name: "SPECIFICATIONS FOR MEDICAL EXAMINATIONS OF COAL MINERS"
positive_law: false
currency: "2026-04-05"
last_updated: "2026-04-05"
format_version: "1.1.0"
generator: "[email protected]"
authority: "Sec. 203, 83 Stat. 763; 30 U.S.C. 843, unless otherwise noted."
regulatory_source: "43 FR 33715, Aug. 1, 1978, unless otherwise noted."
cfr_part: "37"
---


# 37.91 Definitions.

Definitions provided in § 37.2 will have the same meaning in this subpart. Any term defined in the Federal Mine Safety and Health Act of 1977 (Pub. L. 95-164, as amended) and not defined in § 37.2 or this section will have the meaning given it in the Act. As used in this subpart:

*ATS* means American Thoracic Society.

*ERS* means European Respiratory Society.

*FET* means forced expiratory time, which is the time from the beginning of a forced exhalation (the back-extrapolated “time zero”) maneuver to the end of expiration.

*FEV1* means forced expiratory volume in one second, which is the greatest volume of air that can be forcibly blown out within the first second, after full inspiration.

*FEV1/FVC* means the ratio between the largest acceptable FEV1 and the largest acceptable FVC following the forced vital capacity maneuver. It is usually reported as a percentage.

*FEV6* means forced expiratory volume in six seconds, which is the greatest volume of air that can forcibly be blown out in six seconds, after full inspiration.

*FVC* means forced vital capacity, which is the greatest volume of air that can forcibly be blown out after full inspiration.

*PEF* means peak expiratory flow, which is the maximal airflow generated during a forced vital capacity maneuver.

*Spirometry test* means a pulmonary function test that measures expiratory volume and airflow rates and may determine the presence and severity of lung function impairments, if such are present.

[81 FR 73286, Oct. 24, 2016]