40 CFR § 1051.805 - What symbols, acronyms, and abbreviations does this part use?

---
identifier: "/us/cfr/t40/s1051.805"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "40 CFR § 1051.805 - What symbols, acronyms, and abbreviations does this part use?"
title_number: 40
title_name: "Protection of Environment"
section_number: "1051.805"
section_name: "What symbols, acronyms, and abbreviations does this part use?"
chapter_name: "ENVIRONMENTAL PROTECTION AGENCY"
subchapter_number: "U"
subchapter_name: "AIR POLLUTION CONTROLS"
part_number: "1051"
part_name: "CONTROL OF EMISSIONS FROM RECREATIONAL ENGINES AND VEHICLES"
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. 7401-7671q."
regulatory_source: "67 FR 68347, Nov. 8, 2002, unless otherwise noted."
cfr_part: "1051"
---


# 1051.805 What symbols, acronyms, and abbreviations does this part use?

The following symbols, acronyms, and abbreviations apply to this part:

°—degrees.

ASTM—American Society for Testing and Materials.

ATV—all-terrain vehicle.

cc—cubic centimeters.

CFR—Code of Federal Regulations.

CH<sub>4</sub> methane.

cm—centimeter.

C—Celsius.

CO—carbon monoxide.

CO<sub>2</sub>—carbon dioxide.

EPA—Environmental Protection Agency.

F—Fahrenheit.

g—grams.

g/gal/day—grams per gallon per test day.

g/m
<sup>2</sup>/day—grams per meter-square per test day.

HC—hydrocarbon.

Hg—mercury.

hr—hours.

km—kilometer.

kW—kilowatt.

LPG—liquefied petroleum gas.

m—meters.

mm—millimeters.

mW—milliwatts.

N<sub>2</sub>O nitrous oxide.

NARA—National Archives and Records Administration.

NMHC—nonmethane hydrocarbons.

NO<sub>X</sub>—oxides of nitrogen (NO and NO<sub>X</sub>).

psig—pounds per square inches of gauge pressure.

rpm—revolutions per minute.

SAE—Society of Automotive Engineers.

SI—spark-ignition.

THC—total hydrocarbon.

THCE—total hydrocarbon equivalent.

U.S.C.—United States Code.

[67 FR 68347, Nov. 8, 2002, as amended at 70 FR 40510, July 13, 2005; 74 FR 56511, Oct. 30, 2009]