40 CFR § 97.203 - Measurements, abbreviations, and acronyms.

---
identifier: "/us/cfr/t40/s97.203"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "40 CFR § 97.203 - Measurements, abbreviations, and acronyms."
title_number: 40
title_name: "Protection of Environment"
section_number: "97.203"
section_name: "Measurements, abbreviations, and acronyms."
chapter_name: "ENVIRONMENTAL PROTECTION AGENCY"
subchapter_number: "C"
subchapter_name: "AIR PROGRAMS"
part_number: "97"
part_name: "FEDERAL NOX BUDGET TRADING PROGRAM, CAIR NOX AND SO2 TRADING PROGRAMS, CSAPR NOX AND SO2 TRADING PROGRAMS, AND TEXAS SO2 TRADING PROGRAM"
positive_law: false
currency: "2026-04-05"
last_updated: "2026-04-05"
format_version: "1.1.0"
generator: "[email protected]"
authority: "42 U.S.C. 7401, 7403, 7410, 7426, 7491, 7601, and 7651,"
regulatory_source: "65 FR 2727, Jan. 18, 2000, unless otherwise noted. 71 FR 25396, 25422, and 25443, Apr. 28, 2006"
cfr_part: "97"
---


# 97.203 Measurements, abbreviations, and acronyms.

Measurements, abbreviations, and acronyms used in this subpart and subparts BBB through III are defined as follows:

Btu—British thermal unit.

CO<sub>2</sub>—carbon dioxide.

H<sub>2</sub>O—water.

Hg—mercury.

hr—hour.

kW—kilowatt electrical.

kWh—kilowatt hour.

lb—pound.

mmBtu—million Btu.

MWe—megawatt electrical.

MWh—megawatt hour.

NO<sub>X</sub>—nitrogen oxides.

O<sub>2</sub>—oxygen.

ppm—parts per million.

scfh—standard cubic feet per hour.

SO<sub>2</sub>—sulfur dioxide.

yr—year.