# 40 CFR § 61.03: Units and abbreviations

> Federal · Regulations · In force

URL: https://www.frixlaw.com/law-library/statutes/ecfr-40-61.03

## Section

- **Citation:** 40 CFR § 61.03
- **Heading:** Units and abbreviations
- **Jurisdiction:** Federal
- **Kind:** Regulations
- **Status:** In force
- **Text as of:** September 22, 2026
- **Source:** Publisher's official text
- **Location:** Title 40—Protection of Environment > CHAPTER I—ENVIRONMENTAL PROTECTION AGENCY > SUBCHAPTER C—AIR PROGRAMS > PART 61—NATIONAL EMISSION STANDARDS FOR HAZARDOUS AIR POLLUTANTS > Subpart A—General Provisions

## Text

Used in this part are abbreviations and symbols of units of measure. These are defined as follows:
(a) System International (SI) units of measure:
A = ampere
g = gram
Hz = hertz
J = joule
K = degree Kelvin
kg = kilogram
m = meter
m
2 = square meter
m
3 = cubic meter
mg = milligram = 10−3gram
mm = millimeter = 10−3meter
Mg = megagram = 10
6gram
mol = mole
N = newton
ng = nanogram = 10−9gram
nm = nanometer = 10−9meter
Pa = pascal
s = second
V = volt
W = watt
Ω = ohm
µg = microgram = 10−6gram
(b) Other units of measure:
°C = degree Celsius (centigrade)
cfm = cubic feet per minute
cc = cubic centimeter
Ci = curie
d = day
°F = degree Fahrenheit
ft
2 = square feet
ft
3 = cubic feet
gal = gallon
in = inch
in Hg = inches of mercury
in H2O = inches of water
l = liter
lb = pound
lpm = liter per minute
min = minute
ml = milliliter = 10−3liter
mrem = millirem = 10−3 rem
oz = ounces
pCi = picocurie = 10−12 curie
psig = pounds per square inch gage
°R = degree Rankine
µl = microliter = 10−6liter
v/v = volume per volume
yd
2 = square yards
yr = year
(c) Chemical nomenclature:
Be = beryllium
Hg = mercury
H2O = water
(d) Miscellaneous:
act = actual
avg = average
I.D. = inside diameter
M = molar
N = normal
O.D. = outside diameter
% = percent
std = standard
[42 FR 51574, Sept. 29, 1977, as amended at 54 FR 51704, Dec. 15, 1989]

## Nearby sections

- [40 CFR § 61.01 § 61.01 Lists of pollutants and applicability of part 61.](https://www.frixlaw.com/law-library/statutes/ecfr-40-61.01.md)
- [40 CFR § 61.02 § 61.02 Definitions.](https://www.frixlaw.com/law-library/statutes/ecfr-40-61.02.md)
- [40 CFR § 61.03 § 61.03 Units and abbreviations.](https://www.frixlaw.com/law-library/statutes/ecfr-40-61.03.md)
- [40 CFR § 61.04 § 61.04 Address.](https://www.frixlaw.com/law-library/statutes/ecfr-40-61.04.md)
- [40 CFR § 61.05 § 61.05 Prohibited activities.](https://www.frixlaw.com/law-library/statutes/ecfr-40-61.05.md)
- [40 CFR § 61.06 § 61.06 Determination of construction or modification.](https://www.frixlaw.com/law-library/statutes/ecfr-40-61.06.md)
- [40 CFR § 61.07 § 61.07 Application for approval of construction or modification.](https://www.frixlaw.com/law-library/statutes/ecfr-40-61.07.md)
- [40 CFR § 61.08 § 61.08 Approval of construction or modification.](https://www.frixlaw.com/law-library/statutes/ecfr-40-61.08.md)
- [40 CFR § 61.09 § 61.09 Notification of startup.](https://www.frixlaw.com/law-library/statutes/ecfr-40-61.09.md)
- [40 CFR § 61.10 § 61.10 Source reporting and waiver request.](https://www.frixlaw.com/law-library/statutes/ecfr-40-61.10.md)
- [40 CFR § 61.11 § 61.11 Waiver of compliance.](https://www.frixlaw.com/law-library/statutes/ecfr-40-61.11.md)
- [40 CFR § 61.12 § 61.12 Compliance with standards and maintenance requirements.](https://www.frixlaw.com/law-library/statutes/ecfr-40-61.12.md)
- [40 CFR § 61.13 § 61.13 Emission tests and waiver of emission tests.](https://www.frixlaw.com/law-library/statutes/ecfr-40-61.13.md)
- [40 CFR § 61.14 § 61.14 Monitoring requirements.](https://www.frixlaw.com/law-library/statutes/ecfr-40-61.14.md)

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Source: Frix Law Library, https://www.frixlaw.com/law-library/statutes/ecfr-40-61.03. Check the current official text before relying on it. Not legal advice.