§1065.1005 Symbols, abbreviations, acronyms, and units of measure.

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The procedures in this part generally follow the International System of Units (SI), as detailed in NIST Special Publication 811, which we incorporate by reference in §1065.1010. See §1065.20 for specific provisions related to these conventions. This section summarizes the way we use symbols, units of measure, and other abbreviations.

(a) Symbols for quantities. This part uses the following symbols and units of measure for various quantities:

Symbol	Quantity	Unit	Unit symbol	Units in terms of SI base units
α	atomic hydrogen-to-carbon ratio	mole per mole	mol/mol	1.
A	area	square meter	m	m.
a₀	intercept of least squares regression
a₁	slope of least squares regression
a_g	acceleration of Earth's gravity	meter per square second	m/s	m· s⁻ .
β	ratio of diameters	meter per meter	m/m	1.
β	atomic oxygen-to-carbon ratio	mole per mole	mol/mol	1.
C	number of carbon atoms in a molecule
c	power-specific carbon mass error coefficient	gram per kilowatt-hour	g/(kW·hr)	3.6⁻ · 10⁻ · m⁻ · s.
C_d	discharge coefficient
C_f	flow coefficient
δ	atomic nitrogen-to-carbon ratio	mole per mole	mol/mol	1.
d	diameter	meter	m	m.
d	power-specific carbon mass rate absolute error coefficent	gram per kilowatt-hour	g/(kW·hr)	3.6⁻ · 10⁻ · m⁻ · s.
DR	dilution ratio	mole per mole	mol/mol	1.
ε	error between a quantity and its reference
∈	difference or error quantity
e	brake-specific emission or fuel consumption	gram per kilowatt hour	g/(kW·hr)	3.6⁻ · 10⁻ · m⁻ · s.
F	F-test statistic
ƒ	frequency	hertz	Hz	s⁻ .
κ	opacity
ƒ_n	angular speed (shaft)	revolutions per minute	r/min	π · 30⁻ · s⁻ .
γ	ratio of specific heats	(joule per kilogram kelvin) per (joule per kilogram kelvin)	(J/(kg·K))/(J/(kg·K))	1.
γ	atomic sulfur-to-carbon ratio	mole per mole	mol/mol	1.
K	correction factor			1.
K_v	calibration coefficient		m · s · K/kg	m · kg⁻ · s · K.
l	length	meter	m	m.
L	limit
μ	viscosity, dynamic	pascal second	Pa·s	m⁻ · kg · s⁻ .
M	molar mass	gram per mole	g/mol	10⁻ · kg · mol⁻ .
m	mass	kilogram	kg	kg.
m	mass rate	kilogram per second	kg/s	kg · s⁻ .
v	viscosity, kinematic	meter squared per second	m/s	m · s⁻ .
N	total number in series
n	amount of substance	mole	mol	mol.
n	amount of substance rate	mole per second	mol/s	mol · s⁻ .
P	power	kilowatt	kW	10 · m · kg · s⁻ .
PF	penetration fraction
p	pressure	pascal	Pa	m⁻ · kg · s⁻ .
ρ	mass density	kilogram per cubic meter	kg/m	m⁻ · kg.
Δ p	differential static pressure	pascal	Pa	m⁻ · kg · s⁻ .
r	ratio of pressures	pascal per pascal	Pa/Pa	1.
r	coefficient of determination
Ra	average surface roughness	micrometer	μm	10⁻ · m.
Re^#	Reynolds number
RF	response factor
RH	relative humidity
σ	non-biased standard deviation
S	Sutherland constant	kelvin	K	K.
SEE	standard error of the estimate
T	absolute temperature	kelvin	K	K.
T	Celsius temperature	degree Celsius	°C	K−273.15.
T	torque (moment of force)	newton meter	N·m	m · kg · s⁻ .
θ	plane angle	degrees	°	rad.
t	time	second	s	s.
Δ t	time interval, period, 1/frequency	second	s	s.
V	volume	cubic meter	m	m.
V	volume rate	cubic meter per second	m/s	m · s⁻ .
W	work	kilowatt-hour	kW·hr	3.6 · 10 · m · kg · s⁻ .
w_C	carbon mass fraction	gram per gram	g/g	1.
x	amount of substance mole fraction.	mole per mole	mol/mol	1.
X	flow-weighted mean concentration	mole per mole	mol/mol	1.
y	generic variable
Z	compressibility factor
See paragraph (f)(2) of this section for the values to use for molar masses. Note that in the cases of NO_X and HC, the regulations specify effective molar masses based on assumed speciation rather than actual speciation.
Note that mole fractions for THC, THCE, NMHC, NMHCE, and NOTHC are expressed on a C₁-equivalent basis.

Symbol	Species
Ar	argon.
C	carbon.
CH ₂ O	formaldehyde.
CH ₂ O ₂	formic acid.
CH ₃ OH	methanol.
CH ₄	methane.
C ₂ H ₄ O	acetaldehyde.
C ₂ H ₅ OH	ethanol.
C ₂ H ₆	ethane.
C ₃ H ₇ OH	propanol.
C ₃ H ₈	propane.
C ₄ H ₁₀	butane.
C ₅ H ₁₂	pentane.
CO	carbon monoxide.
CO ₂	carbon dioxide.
H	atomic hydrogen.
H ₂	molecular hydrogen.
H ₂ O	water.
H ₂ SO ₄	sulfuric acid.
HC	hydrocarbon.
He	helium.
⁸⁵ Kr	krypton 85.
N ₂	molecular nitrogen.
NH ₃	ammonia.
NMHC	nonmethane hydrocarbon.
NMHCE	nonmethane hydrocarbon equivalent.
NMNEHC	nonmethane-nonethane hydrocarbon.
NO	nitric oxide.
NO ₂	nitrogen dioxide.
NO _X	oxides of nitrogen.
N ₂ O	nitrous oxide.
NMOG	nonmethane organic gases.
NONMHC	non-oxygenated nonmethane hydrocarbon.
NOTHC	non-oxygenated total hydrocarbon.
O ₂	molecular oxygen.
OHC	oxygenated hydrocarbon.
²¹⁰ Po	polonium 210.
PM	particulate matter.
S	sulfur.
SVOC	semi-volatile organic compound.
THC	total hydrocarbon.
THCE	total hydrocarbon equivalent.
ZrO ₂	zirconium dioxide.

Symbol	Quantity	Value
μ	micro	10⁻
m	milli	10⁻
c	centi	10⁻
k	kilo	10
M	mega	10

Superscript	Meaning
overbar (such as y )	arithmetic mean.
overdot (such as y )	quantity per unit time.

Subscript	Meaning
a	absolute (e.g., absolute difference or error).
abs	absolute quantity.
act	actual condition.
air	air, dry.
amb	ambient.
atmos	atmospheric.
bkgnd	background.
C	carbon mass.
cal	calibration quantity.
CFV	critical flow venturi.
comb	combined.
comp	composite value.
cor	corrected quantity.
dil	dilution air.
dew	dewpoint.
dexh	diluted exhaust.
dry	dry condition.
dutycycle	duty cycle.
∈	related to a difference or error quantity.
exh	raw exhaust.
exp	expected quantity.
fluid	fluid stream.
fn	feedback speed.
frict	friction.
fuel	fuel consumption.
hi,idle	condition at high-idle.
i	an individual of a series.
idle	condition at idle.
in	quantity in.
init	initial quantity, typically before an emission test.
int	intake air.
j	an individual of a series.
mapped	conditions over which an engine can operate.
max	the maximum (i.e., peak) value expected at the standard over a test interval; not the maximum of an instrument range.
meas	measured quantity.
media	PM sample media.
mix	mixture of diluted exhaust and air.
norm	normalized.
out	quantity out.
P	power.
part	partial quantity.
PDP	positive-displacement pump.
post	after the test interval.
pre	before the test interval.
prod	stoichiometric product.
r	relative (e.g., relative difference or error).
rate	rate (divided by time).
record	record rate.
ref	reference quantity.
rev	revolution.
sat	saturated condition.
s	slip.
span	span quantity.
SSV	subsonic venturi.
std	standard condition.
stroke	engine strokes per power stroke.
T	torque.
test	test quantity.
test,alt	alternate test quantity.
uncor	uncorrected quantity.
vac	vacuum side of the sampling system.
weight	calibration weight.
zero	zero quantity

Symbol	Quantity	mol/mol
γ_Arair	amount of argon in dry air	0.00934
γ_CO2air	amount of carbon dioxide in dry air	0.000375
γ_N2air	amount of nitrogen in dry air	0.78084
γ_O2air	amount of oxygen in dry air	0.209445

Symbol	Quantity	g/mol (10·kg·mol)
M_air	molar mass of dry air	28.96559
M_Ar	molar mass of argon	39.948
M_C	molar mass of carbon	12.0107
M_CH3OH	molar mass of methanol	32.04186
M_C2H5OH	molar mass of ethanol	46.06844
M_C2H4O	molar mass of acetaldehyde	44.05256
M_CH4N2O	molar mass of urea	60.05526
M_C2H6	molar mass of ethane	30.06904
M_C3H8	molar mass of propane	44.09562
M_C3H7OH	molar mass of propanol	60.09502
M_CO	molar mass of carbon monoxide	28.0101
M_CH4	molar mass of methane	16.0425
M_CO2	molar mass of carbon dioxide	44.0095
M_H	molar mass of atomic hydrogen	1.00794
M_H2	molar mass of molecular hydrogen	2.01588
M_H2O	molar mass of water	18.01528
M_CH2O	molar mass of formaldehyde	30.02598
M_He	molar mass of helium	4.002602
M_N	molar mass of atomic nitrogen	14.0067
M_N2	molar mass of molecular nitrogen	28.0134
M_NH3	molar mass of ammonia	17.03052
M_NMHC	effective C1 molar mass of nonmethane hydrocarbon	13.875389
M_NMHCE	effective C1 molar mass of nonmethane hydrocarbon equivalent	13.875389
M_NMNEHC	effective C1 molar mass of nonmethane-nonethane hydrocarbon	13.875389
M_NOx	effective molar mass of oxides of nitrogen	46.0055
M_N2O	molar mass of nitrous oxide	44.0128
M_O	molar mass of atomic oxygen	15.9994
M_O2	molar mass of molecular oxygen	31.9988
M_S	molar mass of sulfur	32.065
M_THC	effective C₁ molar mass of total hydrocarbon	13.875389
M_THCE	effective C₁ molar mass of total hydrocarbon equivalent	13.875389
See paragraph (f)(1) of this section for the composition of dry air.
The effective molar masses of THC, THCE, NMHC, NMHCE, and NMNEHC are defined on a C₁ basis and are based on an atomic hydrogen-to-carbon ratio, α, of 1.85 (with β, γ, and δ equal to zero).
The effective molar mass of NO_X is defined by the molar mass of nitrogen dioxide, NO₂.

Symbol	Quantity	[J/(kg·K)]/[J/(kg·K)]
γ_air	ratio of specific heats for intake air or dilution air	1.399
γ_dil	ratio of specific heats for diluted exhaust	1.399
γ_exh	ratio of specific heats for raw exhaust	1.385

Acronym	Meaning
ABS	acrylonitrile-butadiene-styrene.
ASTM	ASTM International.
BMD	bag mini-diluter.
BSFC	brake-specific fuel consumption.
CARB	California Air Resources Board.
CFR	Code of Federal Regulations.
CFV	critical-flow venturi.
CI	compression-ignition.
CITT	Curb Idle Transmission Torque.
CLD	chemiluminescent detector.
CVS	constant-volume sampler.
DEF	diesel exhaust fluid.
DF	deterioration factor.
ECM	electronic control module.
EFC	electronic flow control.
e.g.	exempli gratia, for example.
EGR	exhaust gas recirculation.
EPA	Environmental Protection Agency.
FEL	Family Emission Limit.
FID	flame-ionization detector.
FTIR	Fourier transform infrared.
GC	gas chromatograph.
GC-ECD	gas chromatograph with an electron-capture detector.
GC-FID	gas chromatograph with a flame ionization detector.
HEPA	high-efficiency particulate air.
IBP	initial boiling point.
IBR	incorporated by reference.
i.e.	id est, in other words.
ISO	International Organization for Standardization.
LPG	liquefied petroleum gas.
MPD	magnetopneumatic detection.
NDIR	nondispersive infrared.
NDUV	nondispersive ultraviolet.
NIST	National Institute for Standards and Technology.
NMC	nonmethane cutter.
PDP	positive-displacement pump.
PEMS	portable emission measurement system.
PFD	partial-flow dilution.
PLOT	porous layer open tubular.
PMD	paramagnetic detection.
PMP	Polymethylpentene.
pt.	a single point at the mean value expected at the standard.
psi	pounds per square inch.
PTFE	polytetrafluoroethylene (commonly known as Teflon^TM).
RE	rounding error.
RESS	rechargeable energy storage system.
RFPF	response factor penetration fraction.
RMC	ramped-modal cycle.
rms	root-mean square.
RTD	resistive temperature detector.
SAW	surface acoustic wave.
SEE	standard error of the estimate.
SSV	subsonic venturi.
SI	spark-ignition.
THC-FID	total hydrocarbon flame ionization detector.
TINV	inverse student t-test function in Microsoft Excel.
UCL	upper confidence limit.
UFM	ultrasonic flow meter.
U.S.C.	United States Code