Technical Report
EPA-AA-SDS8-85-6
Refueling Emissions from Uncontrolled Vehicles
By
Dal© Rothman
and
Robert Johnson
NOTICE
Technical Reports do not necessarily represent final EPA
decisions or positions. They are intended to present
technical analysis of issues using data which are
currently available. The purpose in the release of such
reports is to facilitate the exchange of technical
information and to inform the public of technical
developments which may form the basis for a final EPA
decision, position or regulatory action.
Standards Development and Support Branch
Emission Control Technology Division
Office of Mobile Sources
Office of Air and Radiation
U. S. Environmental Protection Agency

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Table of Contents
Page No.
I,	Background	1
II.	Parameters Affecting Refueling Emissions	1
A.	Differences Between Vehicle Tank
Temperature and Dispensed Fuel Temperature
B.	Dispensed Fuel Temperature
C.	Fuel Volatility (Reid Vapor Pressure)
D.	Vehicle Differences
I, Other Factors
III.	Baseline Refueling Test Program	8
A.	Vehicles and Test Conditions
B.	Test Procedure
1.	Overview
2.	Effects of Vehicle Preconditioning
C.	Test Results
1.	Summary
2.	Parameter Effects
a.	Differences Between Vehicle
Tank Temperature and Dispensed
Fuel Temperature
b.	Dispensed Fuel Temperature
c.	Fuel Volatility (Reid Vapor
Pressure)
d.	Other Parameters
3.	Differences in Vehicles and Vehicle
Configuration
4.	Prediction Equation
a.	Fitted Model
1.	Coefficients
2.	Variabilty
b.	Comparisons to Results from
Other Studies
IV,	Calculation of Nationwide Emission Factors	38
A.	Introduction
B.	Description of Refueling Emission Factors
C.	Calculation of Displacement Emission Factors
1.	Methodology
2.	Sources of Data
3.	Air Quality and Health Effects Scenarios
4.	Consumption Weighting Calculation
5.	Emission Rates
6.	Effects of Fuel Weathering
D.	Conclusions

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I. Background
The Environmental Protection Agency is currently in the
process of developing and evaluating a Federal test procedure
for the measurement of vehicle refueling emissions. Refueling
emissions are of direct concern due to their benzene content
and the potential health effects of exposure to gasoline vapors
in general. Also, they contribute to ozone formation, and are
of particular concern in areas which currently do not meet the
national Ambient Air Quality Standards (NAAQS) for ozone.
This report describes EPA's baseline program to measure
refueling emissions from uncontrolled vehicles, and to
investigate the sensitivity of these emissions to various
parameters. An emission factor equation based upon the various
parameters will be developed that will be used in making
comparisons with the results of other refueling emissions
studies. It will then be used to estimate emission factors
under a range of conditions.
II. Parameters Affecting Refueling Emissions
As was described by Hochhauser and Campion, the generation
of refueling emissions . is a complex process "involving
non-equilibrium, unsteady state interphase heat and mass
transfer in a system where the mode of contact between gas and
liquid cannot be easily defined or modeled."[1] It has been
shown, however, that fairly good estimates of refueling
emissions can be obtained from empirical equations based upon a
few, easy to determine parameters.[1,2,3] Those parameters
that appear to explain the most variability are: 1) the
difference between the temperature of the dispensed fuel and
the tank fuel, 2) the temperature of the dispensed fuel, and 3)
the fuel volatility. Differences in the physical configuration
of vehicles' fuel tanks and fill necks can also affect
refueling emissions, but this is a variable that can not be
easily quantified. A more complete description of each of
these and other parameters considered is given in the following
sections.
A. Differences Between Vehicle Tank Temperature and
Dispensed Fuel Temperature
A major factor in determining the level of refueling
emissions is AT, the difference between the temperature of
the fuel in the vehicle tank and the dispensed fuel
temperature.. The addition of fuel that is warmer than the fuel
in the vehicle tank in turn warms the tank fuel and vapor
space, resulting in the vaporization of additional gasoline and
expansion of the vapor mixture. This condition is known as

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-2-
vapor growth. On the other hand, addition of colder fuel to a
warmer tank cools the fuel in the tank and some of the vapor
present is condensed into liquid. This condition is known as
vapor shrinkage. When both fuels are at the same temperature
(AT » 0) neither vapor growth no vapor shrinkage occurs and
the volumetric refueling losses are almost identical to the
amount of vapor displaced by the incoming gasoline.
Nearly every previous study dealing with vehicle refueling
emissions has recognized the importance of the relationship
between AT and total refueling emissions.[1,2,4,5,6,7,8,9,10,
11,12] This effect is generally expressed as changes in the
ratio of either the volume of vapor displaced, or grams of HC
emitted, to the gallons of fuel dispensed. In all cases, an
inverse relationship between AT and volumetric refueling
emissions has been seen as is illustrated in Figure 1 taken
from a study by the Stanford Research Institute. In general,
the same result holds for the mass of refueling emissions.
However, due to the changing constituents of the vapor, at
larger negative values of AT a positive relationship between
AT and mass emissions results.[1,2,3,6,9] This "turning
over" effect is shown in Figure 2, also taken from the SRI
study.
B. Dispensed Fuel Temperature
The temperature of the dispensed fuel (T0) can exert a
distinct impact upon refueling emissions, separate from its use
in the determination of AT. It has long been known that the
amount of vaporization of gasoline varies directly with
temperature. This is the reason that mixture enrichment
devices are required for cold starting. All other factors
being equal, emissions would therefore be lower at colder
dispensed temperatures, since less fuel would be vaporized.*
Several of the previous studies have considered the effect
of dispensed temperature upon refueling emissions.[1,2,3,4,6]
In several of these, the value of AT is not separately
computed and controlled, so it is difficult to separate the
distinct effects that the dispensed fuel temperature has on
refueling emissions from its role in vapor growth or
shrinkage. Figures 3 and 4, however, show the effect of
dispensed fuel temperature, when AT is also accounted for, as
seen in two of the previous studies.[1,6]
*It is interesting to note that this will not be the case
for the temperature of the tank fuel (Tt). Lowering
Tt at a constant T0 will create lower values of AT,
resulting in vapor growth and increased emissions.

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P.6
-3-
Q JO
IMY1AU MIL: ' OALLOMS
a to ocTonn 12 oatai
I3X
5&•
a«
0.2
-0.2
PUEL TEM«BATUB6 —
-0.8
•20
NlTIAL TANIt
TEMPERATURE MINUS OlSPENSEO
-30
6BSUS INITIAL
Institute (9)
VOLUME RATIO V
FIGURE 1 VAPOR-LIQUID
Stanford Research
Source •.

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-4-
0MKN9C0 PVtt
• 9 (mMm*
>0 (UHqri
IS Qilton*
» Gdkm
mm*t nut.- s a*txow»
-30	-20	-10	0	i(J	20	30
INITIAL TANK TEMPERATURE MINUS OlSPENSiO PUEl TEMPESAfuaE
SA-JJ30-UA
FIGURE 2 GRAMS VAPOR PER GALLON FUEL VERSUS INITIAL AT
Source: Stanford Research Institute (9)

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EFFECT OF DISPENSED TEMPERATURE
¥i
S.O -
ojo
•JO.OO
-10QO
ST (0IGBES3 F)
	DISP. TEMP.=70
tOjOO	JOjOO
-»—oiap. TiMP.=sa
-0—oiar. TiMP.=as
FlGURE 3
Source: EPA Report 75-Gas~6 Part II, August 15,1975, as cited
by Scott Environmental (6)
9.0
3
o
•s^
«
-o—OISP. TIk#.»30
1 0.0	1 2j0
RtID VAPCK PWEaSLRE (PSH
1 4 JO
-oisp. TiMP.aao
" • « IOC A
¦ »	DI9F. -m». = 9C

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-6-
C.	Fuel Volatility (Reid Vapor Pressure)
RVP is a measure of "front-end" volatility, or the ease of
vaporization of gasoline at 100°F; the higher the RVP the
greater the vaporization potential. Refueling events occur near
this temperature, therefore refueling emission rates should
vary with RVP; all other factors being equal, higher RVP fuel
yielding higher emissions.
In many of the previous studies, the RVP of the fuel, its *
effect being recognized, was held constant. Other studies have
attempted to explore the relationship between RVP and refueling
emissions in a quantitative fashion.[1,2,4,6,9] Figures 5 and
6 show characteristic increases in refueling emissions at a
higher RVP.[1,6] This relationship is also noted in other
studies.
A few studies have also considered the effect of
dispensing a fuel of one RVP into a tank with residual fuel of
a different, lower RVP.[3,9] The general result is larger
vapor growth as a result of the dispensed fuel vaporizing to
increase the hydrocarbon concentration in the tank to the
higher vapor pressure of the dispensed fuel.
D.	Vehicle Differences
As with any type of emissions, there will be differences
in results from different vehicles. In the case of refueling
emissions, these differences are primarily related to the
vehicle's fuel tank system.
Fuel tanks vary in size, shape, position of the fillpipe
(i.e., rear fill or side fill), fill neck design, and internal
baffling. Differences in the areas of the evaporative
surfaces, effective height of the fillpipe over the evaporative
surface and turbulent interactions between the entering fuel
and existing vapors are among the most likely causes for the
differences that are observed in refueling emissions between
vehicles.
Few of the previous studies on vehicle refueling, emissions
have specifically addressed the issue of differences between
vehicles in terms of emissions. This is due predominantly to
the fact that most of these studies were concerned with the
efficiency of various control strategies, and the percentage of
vapor recovered was of more interest than total emissions.
Still, Scott Environmental Technology noted the strong vehicle
effect on refueling emissions as evidenced by the increased
variability in their results as larger numbers of different
type vehicles were used.[6] Stanford Research Institute has

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-7-
EFFECT OF FUEL VOLATILITY
«1
3
a
7.0
a.o
S.0
4.0 -
SjO
2.0 -
1 JO
OjO


1

a

t		 __

+• ~~ ~~ —

+4.
i

""" 0 \

% \
\

N \

\

N \

-x V



N
•30.00
•iojoo
1OJO0
JOjOO
iiT ijsicptfa ri
	~ —ffvF= 1 2.0		4	*VF=8JI
FIGURE 5
Source: EPA Report 75-Gas-6 Part II, August 15,1975, as cited
by Scott Environmental (6)
f
I
©
2.0 -
TO.00
90.00
JO.OO
SO.OO
0I9PIN«D TEk#»EPATURS t'F't
•PMPsT		ftFa 1 O	>?• —- »f#a 1 J
	 FIGURE S

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-8-
noted not only changes in emissions between vehicles, but also
a change- in the shape of the regression line relating refueling
losses to AT.[9] Also, Exxon Research and Engineering has
found average losses at the same test conditions ranging from
4.5 to 5.4 gm/gal depending on the vehicle.[13] Thus, although
the previous studies have not specifically addressed the issue
of differences between vehicles, its effect has been noted.
E. Other Factors
Several other factors that may have an effect upon
refueling emissions have been considered in previous studies.
Among these are: fill rate, [1,9] amount of residual fuel in
the tank,[3,9] total amount of fill,[1,3,9] position of nozzle
in the fill-neck,[9] and ambient temperature.[3,8,9] The
magnitude of these effects is much less than that for any of
the factors described previously. Therefore, this study has
been designed primarily to determine the effects of AT,
dispensed temperature, and fuel volatility; and any insights
that can be obtained about these other effects or differences
between vehicles, will be secondary.
Ill. Baseline Refueling Test Program
A. Vehicles and Test Conditions
Eight vehicles in all have been tested in the baseline
program. These consist of six light-duty gasoline vehicles and
two light-duty gasoline trucks. The tank sizes vary from
vehicle to vehicle, as do the configurations of the tanks and
their internal baffling. A listing of the vehicles is given in
Table 1.
The majority of the testing was performed on the 1983
Cutlass Supreme, as it was the first vehicle tested. The
matrix of parameter conditions under which the Cutlass was
tested is shown in Table 2, along with similar but less
extensive matrices for the 1984 Escort and the 1983 Reliant.
The testing of these vehicles at the various parameter
conditions allows for a more complete comparison of the
differences in refueling emissions between vehicles. Of
particular interest here is the difference in refueling
emissions between side-fill and rear-fill vehicles. Of all the
vehicles tested, only the 1983 Cutlass Supreme is a rear-fill
vehicle, and the future fleet is expected to be dominated by
side-fill vehicles.
The remaining vehicles were tested	primarily at one set	of
parameter conditions. By testing	several	vehicles,	an
indication of the range of refueling	emission	rates can	be
obtained.

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-9-
Table 1

Vehicles
Tested

Year
Make/Model Tank Vol. (gal)
Comments
1983
Olds. Cutlass Supreme
18. l
Rear fill
1983
Buick Skylark
14.5

1984
Chevrolet Celebrity
16.4
Fuel Injected
1984
Ford Escort
13.0

1983
LDT Crown Victoria
18.0
Vertical Tank
1983
Plymouth Reliant
13.0

1979
Dodge Truck W150
18.0

1979
Chevrolet 3/4 Ton


Pickup
19.6


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Table 2
Refueling Emissions Test Matrix
1983 Oldsraobile Cutlass
Fuel	Dispensed Temperature Tank Temperature
9.0 RVP
82 °F
80, 92,
100, 120 °F

929F
80, 92,
100, 120 9 F
11.9 RVP
82 °F
80, 92,
100, 1209 F

92 9 F
80, 92,
100, 1209 F
10.0 RVP
92 °F
80, 92,
1009F
12.6 RVP
82 °F
80, 92,
1009 F

1984 Ford Escort


Fuel
Dispensed Temperature
Tank Temperature
9.0 RVP
80° F
82, 92,
100 °F

92'F
929F

11.9 RVP
66'F
720 F


809 F
82, 92,
1009F

92 0 F
92 8 F


1983 Plymoutn Reliant


Fuel
Dispensed Temperature
Tank Temperature
9.0 RVP
66' F
72 9 F

11.9 RVP
66'F
72 0 F


80'F
82, 92, 100°F

92 ° F
92 0 F


Remaining Venicles


Fuel
Dispensed Temperature
Tank Temperature
11.9 RVP
80, 92 0F
92'F


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-11-
B. Test Procedure
1.	Overview
The refueling emissions tests were performed in the manner
outlined in Table 3. The test vehicle was pushed into the
Sealed Housing for Evaporative Determination 
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-12-
Table 3
Test Sequence
1.	Drain and refuel tank to 10 percent of fuel capacity.
2.	Push vehicle into shed.
3.	Connect heat blankets and thermocouples.
4.	Heat vehicle tank to desired temperature.
5.	Insect fuel nozzle.
6.	Close shed and start mixing fans,
7.	Take initial sample reading (using FID).
8.	Refuel tank to 95 percent of fuel capacity.
9.	Check for spills and nozzle shutoff.
10.	Take final sample reading (using FID).
11.	Disconnect heat blankets and thermocouples.
12.	Remove vehicle from shed.

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-13-
with the . vapor temperature lagging behind the liquid
temperature by several degrees. At the time of refueling, it
was unclear as to whether an equilibrium existed in the
vehicle's fuel tank.
The use of dual heating blankets (the second blanket being
used to heat the top of the fuel tank) drastically reduced the
heating time required, and alleviated the problem of
temperature stratification in the fuel tank. This approach was
therefore adopted as the standard tank heating procedure.
Figures 7, 8, and 9 show the results of the refueling
tests for various methods of vehicle preconditioning. These
data are solely from tests on the 1983 Cutlass, at a constant
RVP and dispensed temperature in each case. Figure 7 gives a
comparison of the results when the vehicle was heated by a
single blanket, heated by dual blankets, or driven on a road
circuit. Figure 8 shows further results when the vehicle was
heated by dual blankets compared to when it was driven on a
road circuit. Finally, Figure 9 shows the results of tests in
which the vapor and fuel temperatures inside the vehicle's fuel
tank were permitted to differ markedly.
Several conclusions can be drawn from these test results.
Refueling emissions were lower by approximately 0.7 gm/gal when
under single blanket heating versus dual blanket heating.
Large differences in the fuel tank liquid and vapor
temperatures may affect refueling emissions, with lower
emissions resulting when the vapor temperature lags behind the
liquid temperature. The results from the road circuit tests
appear to fit better with the single blanket tests, but half of
these also fit with the dual blanket tests fairly well.**
It is unclear how much of the difference between the
single and dual blanket test results can be explained by the
temperature stratification in the vehicle's fuel tank, and what
must be explained by other factors. Because of its heating
time advantages, and the question of tank equilibrium, dual
blanket heating was used in the actual baseline testing. The
results from the tests on the vehicle prepared on the road
circuit, which are taken to represent a real-life situation,
suggest that the dual blanket heating procedure may yield
slightly conservative, but generally accurate, estimates of
refueling emissions in real life situations.
When 90 percent confidence intervals for the regression
lines are used.

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-JEHiasEpPKCO®n^NlNG EFFECTS
ID i .B"
OUflu
ROPO
in H.BB
H
T cdegrees F
RVP
= I c • 0 0 I 5P • T
rtfp . =32
s. aa
B . SB
DUBL blanket
RDPO PRCP
-is.
B -10.0
-C.B
a .a
s. a
ia.a

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LRRGE INTERNRL TRNK TEMP. DIEE
RVP= I 1.3 D I 5P . TEMP . =32
12.0
I
in
10.0-
\ 3.0 h
b . m
ID
\J -j . 0
LIT
LdB-B
in
ui
~ M.0
*m i j
£. 0
3. m
*	V.T.=L.T.
*	V . T . < < L . T
*	V . T . > >L . T
I S . 0
S . 0
£ . 0
I S . 0
25 . 0
at* C DFRRFF^ p }
•¦¦•M	*	Wmmmr	M» VriaaJ •	v ILn — —	¦urn ¦ 1	i
FIGURE 9

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-16-
C. Test Results
1.	Summary
It has been found that the refueling emissions, in grams
of HC per gallon of fuel dispensed, can be estimated accurately
by a multiple linear regression model relating refueling
emissions to the difference between vehicle tank temperature
and dispensed fuel temperature (AT), the dispensed fuel
temperature, and the fuel volatility. The effects of vehicle
configuration were explored and found to be of some
significance.* The following general conclusions can be
reached from the results.
a)	lower tank temperatures, relative to the dispensed
fuel temperature, yield higher emissions,
b)	higher dispensed temperatures yield higher emissions,
c)	higher RVP dispensed fuel yields higher emissions;
and,
d)	vehicle configuration can have a significant impact
on refueling emissions.
A more detailed look at each of these factors follows.
2.	Parameter Effects
a. Differences Between Vehicle Tank Temperature and
Dispensed Fuel Temperature
Due to the phenomena of vapor shrinkage and vapor growth
the difference between the tank temperature and the dispensed
fuel temperature has a significant impact upon refueling
emissions. This difference is defined herein as Tt - T0
and will be referred to as AT. The tank temperature, TT/
is measured as the liquid temperature in the vehicle fuel tank.
Figure 10 shows a plot of refueling emissions against
AT. The general trend of higher emissions at ' lower AT
values, representing more vapor growth, is apparent even when
other factors such as dispensed temperature and fuel volatility
are not considered. Very few tests were run at negative values
of AT, and none below AT= -12, so the turnover in the
The results of all of the valid tests performed on each
vehicle are summarized in Appendix A. This includes the
special tests run on the Cutlass in addition to the
primary baseline testing.

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REFUELING LOSSES vs. Tt*»i!-T9isMiisi(
m
13.500
12.000 ~	•
10.500 ~	• •
*
~ • • •
~ * •
• *
«
9.0000 *
2 •
• • •
* • • •
•	~* *2	• *
~ ~ • ~
i w
1 f> i
f~- in 7,5000 ~	•	2
1 to	• *3 •
• • •
I Q	•	•	• • *
~.]	»	•	2 •
••	••	2
2 • • »•
~ • •
6.0000 ~	•	* •• • •
O
•z
M
.J	*	**2 2	•
••••«•« ~ #
*
•	• *3	# •	# •	•
4,5000 *	•	~ ~	2
~ • • »• «
• ~ ~
~
3.nooo ~
1 .5000 ~
°. ~
		4	~	»	*	*	»	»	«	»	»	~	»	*		»	»	*	*
-14.000	.00000	14.000	28.000	42.000
-7.0000	7.0000	?l.000	35.000	49.000
Tt*nk-Ti>iif*«si» <"F>
FIGURE 10

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-18-
relationship between AT and mass emissions noted earlier from
other studies is not seen here.
b.	Dispensed Fuel Temperature
Figures 11 and 12 illustrate the effect that the dispensed
fuel temperature can have upon refueling emissions. These
plots are separated by fuel volatility, and the refueling
emissions values are plotted against AT in order that the
effects of dispensed temperature can be separated from these
other parameters. The values plotted at each AT are the mean
responses, along with the standard deviation of the observed
test results (where applicable) for a range of ATs centered
at that point. A smaller standard deviation at a given point
in these plots will not necessarily mean a more precise point,
as the same number of tests were not performed at each point.
They are presented here solely to give an indication of the
variation in the test results.
The figures indicate in general that higher dispensed
temperatures will yield higher refueling emissions. This is
especially true at values of AT around 0F° where a 10°F
change in T0 produces a 1 gm/gal change in emissions, with
the effect being less notable at higher values of AT, where
all values tend to converge. These results are consistent with
those seen in previous studies.
c.	Fuel Volatility (Reid Vapor Pressure)
Figures 13 and 14 illustrate the effect that the fuel
volatility can have upon refueling emissions. The form of
these plots is the same as in those used to illustrate the
effect of dispensed fuel temperature, only here the dispensed
fuel temperature is held constant as opposed to the fuel
volatility being fixed previously.
These figures give a clear indication that a higher fuel
volatility, denoted by a higher RVP, will yield higher
refueling emissions, as was seen in other studies. As with the
dispensed fuel temperature, this effect is more noticeable at
low values of AT.
Several tests were run where a fuel with a lower
volatility than the dispensed fuel was placed in the vehicle's
fuel tank. This represents the case in which a vehicle's fuel
weathers and loses some of its volatility between refuelings.
The expected result, as described in the SRI study, is higher
emissions resulting from vaporization of the dispensed fuel to
increase the hydrocarbon concentration in the fuel tank to the
higher vapor pressure at the dispensed fuel. The results from
these tests are shown in Figure 14 as the three single points*,
and reaffirm the results in the SRI study.[2]

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-19-
DISPENSED TEMPERATURE EFFECTS

RMP- 9 0 PS I
oisp temp.«a2 f
0 ISP. TEMP. »32 F
7 ..00

6. az
S.0B
W
3. 00
a. a
0
0
AT C DEGREES F )
rvp=ii.a PSi
DlSP.TEMP.-82 r
DISP.TEMP.-32 T
>0.0
6 . 0
in s.0
~ * • a ;*
j ~
i a. a
«j a
ia.ii
20 . 0
30.0
. 0
AT (DEGREES F)
FIGURES 11 and 12

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-20- .
FUEL VOLATILITY EFFECTS
DISPENSED TEriPERR7U = E
5 2 F
3 - 20
CVP: 9 0 PS 1
RvPsii g ps|
fVP*i2 6 PS
a. aa
7. za
6. aa
c. aa
M . am
3. ae
i a. a
a ^ a
i a. a
2e. a
38 . 0
AT C DEGREES F)
DISPENSED TEMPERRTURE 32 F
fVP" 9 .0 PS I
Hvp-ia.a psi
.0
r\
0.0
0
0
0
V
.0
0
0
3.0
AT (DEGREES F >

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-21-
d. Qther Parameters
It has been suggested that other parameters, such as
ambient temperature and fuel dispensing rate may influence
refueling emissions. In this particular testing program, it
appears that the time required to heat the vehicle's fuel tank
and the dispensing rate of the fuel may be of some
significance. The design of this program, however, has made
any significant analysis of these effects virtually
impossible. Thus, although the presence of these effects are
recognized, they cannot be determined here. Also, in
comparison to the effects due to AT, the dispensed fuel
temperature, fuel volatility, and vehicle configuration
(discussed in the next section), these other effects are of
much lesser significance.
3. Differences in Vehicles and Vehicle Configuration
For most of the vehicles tested, there is insufficient
data to do independent parameter analyses. Therefore, a
multiple linear regression has been fit using all of the data,
and the residuals, the actual values minus the values predicted
by the regression equation, have been examined.. The different
patterns in the residuals from vehicle to vehicle can give an
indication of the vehicle effects. Figures 15-22 show the
residuals plotted against the predicted values for each vehicle
individually, all plotted at the same scale.
Of particular interest in these residual plots are the
residuals associated with the LTD Crown Victoria, the Escort,
and the Reliant. The residuals associated with the LTD are
quite extreme, higher than those associated with any of the
other vehicles aside from a few tests on the 1983 Cutlass.
This may be due to the LDT's unique fuel tank configuration;
its height dimension being larger than its width, with almost
no drop in the fill neck. This configuration is atypical of
the automotive fleet, and the results from the tests on the LTD
would skew the prediction equation derived from the multiple
linear regression model. Thus, although the LTD shows the
potential range in refueling emission rates, its test results
have not been used in formulating the prediction equation to be
used here.
The results are also listed in Appendix A under the
heading Fuel Weathering Tests.

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-22-
1983 Olds. Cutlass Suprsne
«
a
w
0
gg « ir*
«»
0
OB- i>n
1984 Rsrd Escort
Predicted (gm/gal)
Predicted (gm/gal)
1983 LID Crown Victoria
Predicted (gm/gal)
m
at
s
E
at
I f*rm
9 lift
1983 Plymouth Reliant
Predicted (gm/gal)
eiftURGS 1S-18
RESIDUAL PLOTS BY VEHICLE

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-23-
1983 Buick Skylark
1984 Chev. Celebrity
*
I.
m
3
•o
fl»
0
<1
m
*
a
m
9
a - "•*
Predicted (g«i/gal)
Predicted (gm/gal)
1979 Dodge Truck W150
«
m
s
6
01
3
"O
(A
e
OB
1979 Chev, 3/4 ton Pickup
Predicted (gm/gal)
Predicted (gm/gal)
FIGURES 19-22 RESIDUAL PLOTS BY VEHICLE

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-24-
The residual plots associated with the Escort and Reliant
both show a distinct pattern of underestimation of refueling
losses (positive residuals) at low predicted values, and
overestimation of higher predicted values. This would indicate
that the fitted model here, dominated by data from the
rear-filled 1983 Cutlass, may not be the most accurate for
other vehicles, particularly side-filled vehicles which have a
large vertical drop in the fill neck.
A further comparison can be made by fitting a multiple
linear regression model, based upon the same parameters as
discussed before, for the Cutlass test results and for the
Escort test results. These are the only two vehicles that have
large enough data bases to make reasonable parameter
estimates. The resulting fitted models are as follows:
Cutlass: Refueling Loss (gm/gal) =
-5.584 - 0.114[AT(°F)] + 0.0857[TD(°F)] + 0.520[RVP(psi)]
R2 = 0.856
Escort: Refueling Loss (gm/gal) =
-6.687 - 0.039[AT(°F)] + 0.081[To(°F)] + 0.545[RVP(psi)]
R2 = 0.912
The resulting equation indicates that the primary differences
in refueling emission between these vehicles lies in the amount
of vapor shrinkage or vapor growth that occurs during the
refueling event. These processes would naturally be related to
vehicle configuration, so this result appears reasonable.
A few more insights can be gained from an examination of
the residual plots. Aside from the Celebrity whose residuals
are consistently negative, although not as extreme as those for
the LTD, the residuals for all vehicles generally fall within
+ 1 gm/gal. This includes the test results from the two light-
duty trucks which agree well with the prediction equation, even
though it is based primarily upon automobile tests.
In summary, it is clear that differences do exist from
vehicle to vehicle. Nevertheless, an equation based upon all
of the data, except the LTD tests for reasons as noted before,
appears to work well on average.
4. Prediction Equation
a. Fitted Model
A primary goal of this study has been to develop an
emission factor equation based upon the parameters that affect
refueling emissions. This has been achieved by fitting a

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-25-
multiple linear regression model with the data from seven of
the eight vehicles tested.*
The prediction equation developed for refueling emissions
from an uncontrolled vehicle is given as follows:
Refueling Loss (gm/gal) =
-5.909 - 0.0949[AT(°F)] + 0.0884[T0(°F)] + 0.485[RVP(psi)]
R1 = 0.786
MSE - 0.732
This equation will be used to estimate emission factors
under a range of conditions, and also will be compared with
results from other refueling emission studies. The range of
conditions over which actual tests were made is given below:
T0 - 66-68°F; RVP = 9.0-11.9 psi; AT = 0 to 10°F
To = 78-85°F; RVP => 9.0-12.6 psi; AT = -2 to 40F°
To = 88-95°F; RVP » 9.0-11.9 psi; AT » -12 to 32F°
1. Coefficients
Each of the parameters included in the regression model is
statistically significant at a confidence of 99.9 percent,
i.e., there is less than a 0.1 percent probability that any of
the three parameters has no effect upon refueling emissions.
The magnitude of the effects due to each parameter is given by
the associated coefficient in the regression equation. A 10F°
increase in AT will lower refueling emissions by nearly 1
gm/gal; a 10°F increase in T0 will increase refueling
emissions nearly 1 gm/gal; and a 1 psi increase in RVP will
increase refueling emissions nearly 0.5 gm/gal.
There was some consideration as to whether a linear model
is sufficient to explain the data over the range of conditions
where the regression equation is applicable. A look at the
residuals (actual gm/gal minus predicted gm/gal) can give an
indication as to whether the assumption of linearity is
appropriate. Figures 23-26 show the residuals plotted against
the predicted values and against each independent parameter.
The residual scatter in these plots appears random, and no
systematic trends are evident, which would indicate significant
nonlinearity. Also, several other forms of the regression were
considered in which interaction and nonlinear terms were
included. These are presented in Table 4, along with the
associated R*. The R2 value is a measure, of a model's
Does not include testing on the LTD or the special tests
on the 1983 Cutlass (single blanket, etc.)

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Table 4
Alternative Formulations of Regression Model
Form of Model	,	R1
Gm/Gal =¦
1)	exp [a,+al(TT)+al(RVP)+a,(T0)(TT)+
ay(To)(RVP)]	.805
2)	exp [ao+al(TT)^aJ(To)+
a,(RVP)]	.823
3)	a,+a1(TD)+aJ(T0)(TT)+
a,(T|)(T|)	,613
4)	a0+ai(AT)+a*(AT1)+a»(T0)+
a,(RVP)	,790
5)	a0+ai(AT)+a2(T0)+
a,(RVP)	,786

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PREDICTED VALUES
RESIDUAL VALUES VS.
Fitted Model All Vehicles
2.5000
7.0000
I .5000
I.oouo
I .50000
e •
t 24564-»«~"
I
m	+
n
a
e
-.50000 ~
• •
-1 .0000
~--r
10.000
i uuuu
>	6.4444
PREDICTED (gm/gal>

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RESIDUAL VALUES VS. Ttamic-To I
.5000
.0000
. SOOQ •
I.0000 *
.50000
• •
~ 2
• •
• • •
2 •	..
... «
.
...»
. • • 2 •
.00000 *		••
?—»•——^
> « « •
2

-.50000 ~
-1.0000 *
-1.5000 *
... •
• . . •
...
. »
. .»
. . •
. *2
... 2 1
. .
			~	
,	~			~"** *	42.000
^ UOUtJ '			14 ~ 000	28000 36.000	49 000
. OUllOO	2 1 000 "
-,40U0	uuou	> 0000
_	/ • *? \

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2.5000
RESIDUAL VALUES vs. DISPENSED TEMPERATURE
2.0000 ~
1.5000 *
~ *
• •
I . oopo «
• •
.50000 #
~ •	~ 2 •
~ ~	*
~ *
2	2 •
•	4
~	2 •
•	• 3 *
.00000 *-
>• • •
2 ~
•	• • 2
•	•
.50000
1.0000 *
2 ~	~
•	j
• * • •
~	~ •	i
~	• 3 ~
• ••
• •
• • •
• • • •
• • •
** • 3 •
•	2*
• • •
.5000 ~
• •
2.000U
~ — -
60.000
	#	t	_ t	#	t _		«¦	' * * - - _ -	4.-.
68.000	76 000	84,000	92.000
64,000	7 2.000	SO.000	86.000.	96.000

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RESIDUAL VALUES vs. FUEL VOLATILITY
2.5000 ~
00
0»
2.0000
). &000
I 0000
.50000
s!
5 .00000
a
n
(0
l.0000
I.0000
1.5000


2


3
2

3


•
4

3


4
•
•
4
4
2
4


2
•

4
2
2
5
3
»
2
•




9
3

4
J

5
4

2
2

5
4 ,

5
i

•
•

3
2

2
5


3

5
3
•
2


3
•

2
•




2


•


•


•


•


•
uuu
a ouoo
M t»UU0
10.500
10.000
I 1 .000
i I .500
12.000

I
u>
0
1
12.500
- - - »
13.000

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li-
ability to. predict trends that are presented in the data.
These results show that the linear model is sufficient to model
the baseline refueling data, and its simpler form makes it
easier to interpret.
2. Variability
There is a large amount of variability in the results from
the refueling emission tests; values ranged from under 3.0
gm/gal to over 11.0 gm/gal. Nearly 80 percent of this
variation is explained by the three parameters: T0, AT,
and RVP, as indicated by the RJ value associated with the
regression model. However, a fair amount of variability
remains unexplained as shown by the mean squared error value of
0.557 gm/gal.
Much of the remaining variability is due to the
differences in vehicles as discussed before, but other factors
are also involved. Several parts of the test procedure are
subject to certain degrees of error, and can therefore lead to
test variability. The first of these involves the heating of
the fuel tank in the vehicle as mentioned before. What effect
the heating rate may have is unclear. The same can also be
stated for the dispensing rate of the fuel. The heating of the
dispensed fuel in the fuel cart also vp-ies somewhat, and could
very possibly slightly affect the RVP of the fuel.
All of the above effects are generally negligible,
however, in comparison to the effects caused by even a small
fuel spill or spitback at the end of a refueling. Tests in
which spills estimated at over 1/2 of a cup occurred were
generally voided, except where no significant effect was
noted. However, even a spill as small as 1 1/2 tablespoon
could generate a one gram per gallon increase in emissions if
it were to completely evaporate.* The concern over spills was
large enough to change the test procedure used in this program
to call for manual shutoff of the dispensed fuel. Also, the
effect is large enough to warrant being considered in
determining the total emission factor. This will be discussed
more in the sections dealing with the refueling emission factor.
b. Comparisons to Results from Other Studies
The prediction equation derived here can be: 1) used to
make comparisons with the results measured from other studies,
and 2) compared to prediction equations derived elsewhere. A
brief summary of the results from other studies, and how they
compare to those in this study, is given in Table 5. Overall
the results of this study are in good agreement with past work.
* Using 10 grams/tablespoon and assuming a 15 gallon refueling

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-32-
Table S
Summary of Results from Previous Studies
Year
1975
Study
Scott
To(°P)
55-70
AT(°F) RVF(psi)
•30 to 30 8.8, 12.0
1975
Scott 80-85

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-33-
Table 5 (cont'd)
Summary of Results from Previous Studies
Year
Study
1975
Study
SRI
To(°F)
Comments & Relation
AT(°F) RVP(psi) to Current
68-85 -30 to 45 6.9-8.6(10.6)
1976
ER&E
10-100 -20 to 10 7-13
1976
Union 75-85 -20 to 30 8.8-9.0
a
a
fuel
Tests at
station on
vehIcIe
tank;
comprehensive
tests looking at
many independent
variables that
affect refueling
emissions; good
general agreement
with	current
study; slightly
low at low ATs
and higher at
high ATs.
Fuel tank tested
in	controlled
envi ronment;
vapors collected
in Tedlar bag;
yields results
1-1.5	gm/ga t
lower at 0° AT,
nearly equal at
10° AT.
at
29 used
base Iine
Tested
vehicles
refueling
stat ion;
for
results;
est imates
gm/gaI
0°
approx imateIy
equal at AT 10°
random
lower
1
at
AT,

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-34-
Table 5 (cont'd)
Summary of Results from Previous Studies
Comments & Relation
Year Study T0(°F) &T(°F) RVP(psi > to Current Study
1978 ER&E 85 -1	9.1	Looking	at
efficiency of an
onboard control
system on 3
vehicles.
Baseline
estimates .7-1.6
gnt/gal	lower
than predicted
by current study.
1978 Mobil 82-85 0	8.2-12.0 Tests on a
single vehicle.
Good agreement
with predicitons
from current
study.

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-35-
In order to estimate the results from other studies using
the prediction equation, information is required on the test
conditions: fuel RVP, tank temperature, and dispensed fuel
temperature. Also the refueling losses need to be reported in
total grams per gallon of refill, or in a form that can be
readily converted to this form. Only a few of the previous
studies met all of these criteria.
In their tests involving Stage II vapor recovery vapor
balance systems at a retail gasoline station, Scott
Environmental arrived at estimates for uncontrolled
emissions.C6] Their study involved two phases of testing: the
first on thirty control vehicles at a service station and the
second on random vehicles. For each phase, two series of
vehicles were tested. Average RVP and dispensed temperature
are only provided for the two series in the second phase of
testing. These two series yielded baseline emissions of 5.505
and 5.593 gm/gal. The average for the other factors are also
given for these two series; RVP = 8.0286 and 8.6440, dispensed
temperature = 81.265 and 81.0196 °F, and tank temperature =
81.867 and 82.0796 respectively. Using these conditions and
the regression equation derived in this report, estimates of
5.109 and 5.352 gm/gal are obtained. These are slightly lower
than obtained by Scott, but still well within the range of
uncertainty in the data.[6]
In a study done by the Mobil Research and Development
Corporation in 1978 a series of refueling emission tests were
run on a 1978 Pontiac Sunbird. During these tests the vehicle
was equipped with an onboard control system, so the total HC
emissions given is the sum of the HC collected in the canister
and the refueling emissions measured in the SHED. These tests
were performed in a SHED, in the same general manner as the
test in this study, with the only exception being that the
vehicle was preconditioned by driving and not just heating of
the fuel tank.[13]
The Sunbird was tested at the following conditions:
dispensed temperature =¦ 82-85°F, AT = 0F°, and RVP ranging
from 8.2 to I2.01bs. The resulting losses, along with the
estimates from .this study are given below. The equation
derived in this report is not strictly applicable at RVP levels
under 9.0, but the estimates are given here regardless. Mean
estimates from this study are generally on the high end of the
ranges given by Mobil, but also note the variability in their
test results.

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-36-
RVp .	# Tests	Total HC (qro/cral)	This Study1
8.2-8.5	8	3.72-6.82	5.52
8.6-9.0	10	4.2-5.60	5.74
10.3-10.6	3	5.9-7.1	6.54
11.2-11.4	3	5.5-7.0	6.95
11.8-12.0	3	7.0-7.2	7.24
The Stanford Research Institute study involved tests on a
26-gallon General Motors and a 26-gallon Ford fuel tank used in
1973-4 vehicles, at a service station. The results from the
tests on the GM tank at a fill rate of 5.3 gallons per minute
and a fill of 20 gallons are given below along with this
study's estimates at the given conditions.[9] These tests
represent those most similar to this study's testing. Where
the conditions fall within the ranges for which the EPA
equation is applicable, the agreement is good, generally within
.50 gm/gal. Only when the equation is extrapolated far beyond
its applicable range is there a significant disagreement with
the SRI results, illustrating the dangers of such extrapolation.
GM/GAL
AT
Ta.
RVP
SRI[2]
This Study
Difference
-17
79.5
8.5
5.13
6.85
1.7;:
0
80
8.5
5.03
5.28
.25
1
80
8.5
4.82
5.19
.37
2
78
8.5
4,52
4. 92
.40
27
76
8.5
3.07
2.37
-.70
35
79
8.5
2.09
1.88
—. 21
41.5
79.5
8.5
1.26
1.30
.04
43
77
8.5
1.42
0.94
-.48
Exxon Research and Engineering performed a series of tests
on 3 vehicles in 1978, in order to determine the efficiency of
an onboard control system.[13] The vehicles tested were: a
1978 Caprice, a 1978 Pinto, and a 1978 Chevette, and the test
conditions were: AT = -1F°, T0 = 85° F, and RVP » 9.1
psi. The resulting averages for each vehicle, along with
predicted values from this study are given below.
GM/GAL
Vehicle	ER&EC13] This Study
Caprice	4.9	6.1
Pinto	4.5	6.1
Chevette	5.4	6.1
Using 83.5°F and mid-range of RVP interval.

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-37-
In this case, the results from this study appear to
significantly overestimate the Exxon results, especially for
the Pinto. The testing on these vehicles was performed with a
prototype refueling canister on each vehicle, and the tests
were part of a larger test sequence including measurements of
evaporative and exhaust emissions. These differences and
consideration of the fact that a comparison is being made
between individual vehicles and one case and a population
average in the other case can explain some of the discrepency
in the results. Also, these vehicles are older and of a
different fuel tank design than those tested here.
Four prediction equations that consider factors other than
AT have been found in the relevant literature. One of these
has a correlation coefficient, r, of only 0.25 associated with
it, so it has not been included in the analysis here. [4] The
remaining equations, and associated parameter regions where
they are applicable are given below.
CAPE9(EPA)[31
gm/gal » expC-0 . 091703 + 0 . 0011521(RVP) (To ) - O.QQ126Q5(Tt)
+ 0.0 5 4 0 9 4(RVP) + 0.00010725 -20 °F
Union Oi1C 2 3,
gm/gal =» -15.178+0.1503(To)+0.002523(To)(Tt)-0.0000002099(T0)1(Tt)1
Ri = 0.5740 SE - 0.3873 gm/gal
RVP = 8.8 to 9.0 psi
To = 75 to 85 °F
Tt = 70 to 115 °F
The equations determined in the CAPE-9, Exxon and Union
studies are based upon 140, 43, and 29 tests, respectively.Cl,
2,3] The testing done in the CAPE-9 and Exxon studies was

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performed on a vehicle tank in a laboratory setting.[1,3]
Union performed its testing on vehicles refueling at a retail
gasoline station.[2]
As is readily apparent, the form of these three equations
differ among themselves, and from the equation derived in this
study. This makes a direct comparison of the results somewhat
difficult. Figure 27, however, shows plots of refueling losses
versus for each equation and the Stanford results, at a
dispensed temperature of 79°F and an RVP of 8.5 psi. An RVP of
8.5 psi is slightly out of the applicable ranges for the Union
results and those derived here, but the figure is still useful
for comparison. Figure 28 shows a further comparison of this
study's results to earlier work by EPA as cited in the Scott
study.[6] This is shown in a separate figure as the conditions
are slightly different from those show for the other studies.
Figures 27 and 28 show very good general agreement between
the results from the CAPE 9, Stanford, the earlier work by EPA,
and this study, over their applicable ranges of AT. The
studies by Union and Exxon yield somewhat lower estimates of
refueling losses at negative values of AT, but their results
are not radically different. All in all, considering the
differences in testing apparatus and procedures, the results
from the various studies tend to confirm each other and the
results derived here.
Considering the results from these studies, it appears
that the prediction equation derived in this report generally
provides reasonably accurate estimates of refueling emissions
based upon the given parameters within its applicable parameter
ranges. Therefore, there should be no problem in using it to
determine average emission factors and to determine control
system designs and efficiencies.
IV. Calculation of Nationwide Emission Factors
A. Introduction
Analysis of the baseline test data has yielded an equation
that can be used to calculate emission factors representative
of various AT, T0, and RVP conditions within the
approximate limits of the values for the original test
parameters (see section III C 4). Given this ability to
determine emission rates for different conditions, it then
becomes necessary to determine the most representative
conditions in order to calculate a refueling emission factor
that will accurately reflect national uncontrolled in-use
emissions levels. Because the conditions that determine

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COMPARISON Of EPA RESULTS to OTHER STUDIES
RVP = 8.5 c-si PISP.TEMP.
uj
4-0.00
20.00
O.U
0.00
0.00
-40.00
UNION
&— er&e
+ ---SRI
FIGURE 27

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COMPARISON of EPA RESULTS to SCOTT STUDY
-I
«
5
O,
w
ta
w
o
_J
7.0
6,0
•j .u
4.0
3.0
U
1 .0
RVP = 8.8 psi DiSP.TEMP=85 F
0.0
30.00
-o	EPA6 4
10.00	10.00
AT (DEGREES F)
— 4-—SCOTT ENVIRONMENTAL
I
O
I
JLI.OU
FIGURE 28

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-41-
emission rates (basically temperature and volatility of the
fuel) vary from region to region and from season to season
within a given region, it will be necessary to identify
regional and seasonal temperatures and fuel characteristics and
then to apply the appropriate averaging to determine national
emission factors. It is also important to examine seasonal
emission factors to ensure that summer and winter emissions are
not significantly different from the annual average value.
There are two basic uses of a refueling emission factor:
(1) to calculate air quality effects and (2) to determine
health ris)c due to exposure to the pollutant in question. The
air quality effect of VOC from refueling emissions consists of
the role these emissions play in ozone formation. Ozone
formation tends to be a seasonal phenomenon, with most NAAQS
violations occurring during the spring and summer months, i.e,
May through September. The emission factor used in air quality
calculations should therefore appropriately reflect the
conditions that are found during the ozone season.
In addition to their role as ozone precursors, refueling
emissions may also have environmental health effects. Benzene,
a known human carcinogen, is present in small amounts in
gasoline. In addition, recent studies have indicated that other
species of VOC contained in refueling emissions are possible
carcinogens.[15] Although the effect on humans is not fully
known, refueling emissions may pose a health risk to service
station employees, self-service gasoline customers, and persons
residing near service stations. Because such exposure risk
represents a year-round problem, the emission factor used in
determining health risk should represent average annual
conditions, although if there are significant seasonal
variations the additional risk posed by these variations would
have to be evaluated.
The remainder of this report will begin with a discussion
of the total emission factor, which includes both spillage and
displacement losses. An appropriate spillage emission factor
will be selected. The process for developing the displacement
emission factor will then be described in detail, including the
methodology used, sources of data, selection of- seasonal
scenarios for air quality and environmental health effects,
determination of representative temperature and fuel volatility
parameters and emission factors for these scenarios. The
question of seasonal differences in the emission factor will
also be addressed. Finally, a representative national emission
factor for refueling will be presented.

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B. Description of Refueling Emission Factors
There are two types of refueling losses that comprise a
total refueling emission factor. These are spillage of liquid
gasoline during the course of the refueling operation and
displacement losses, or the vapor that is forced out the
fillpipe during refueling. Displacement losses occur during
every refueling operation, while spillage or "spitback" is a
more infrequent occurrence.
1. Spillage Losses
A varying portion of the total refueling loss results from
the spillage of liquid gasoline during the refueling process.
The amount of such spillage can vary from a few drops on the
side of the car or pavement as the fueling nozzle is withdrawn
from the fillpipe to a cup or more spurting out on the ground
as a result of "spitback" due to poor fillneck design or a
malfunctioning fuel nozzle. Probably the majority of spills
are less extreme, coming about as a result of motorists or
service station attendants attempting to "top off" the vehicle
tank by restarting the nozzle after automatic shutoff has
occurred. Such spills are normally not large, on the order of
a tablespoon or so. A spill of one tablespoon leaves a 9 to 10
inch diameter circular spot on the service station pavement and
results in emissions of about 10 grams. Thus on a 10 gallon
fill, the spillage would equal about one gram per gallon of
fuel dispensed. Larger spills such as those accompanying
spitbacks or nozzle malfunctions can lead to significantly
higher emissions. A one-half cup spill for the same 10 gallon
fill leads to emissions of about 8 grams per gallon. Thus,
overall, spills are of concern.
Of course not every fillup, or even every attempt at
"topping off" results in a fuel spill and different amounts of
fuel are spilled each time. Unfortunately very few data are
available regarding either the quantity or the estimated
frequency of fuel spills, and there is considerable variance in
the existing estimates. EPA's emission factor document (AP-42)
presents a value of about 0.30 grams per gallon based on a
comprehensive study conducted by Scott Research Laboratories in
the early I970's.[l6] However, an in-depth review of this
study reveals the authors belief that the- spillage rate
estimates should be viewed as minimum values, rather than
averages, due to the presence of observers, the technique used
to estimate spill amounts, and the fact that the stations
studied were primarily full serve rather than self serve.[17]
However, another EPA contractor report cited an estimate of
1.36 grams per gallon, and a 1980 Calfornia study conducted by

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-43-
the South . Coast Air Quality Management District provided
information which indicated an average spillage rate of about
0.80 grams per gallon for uncontrolled nozzles.[18,19]. it
should be noted that the latter study included the brief period
of fuel shortages in 1979, which may have encouraged an
abnormal amount of "topping off" of fuel tanks and hence
slightly higher than normal spillage. The wide variation in
the available data on spillage rates (more than a factor of
four among the three studies) is of some concern. While there
appears to be good reason for the variation, the data is
inadequate to allow determination of a revised emission
factor. In the absence of more definitive information on this
topic, the .30 grams/gallon rate contained in AP-42 seems to
represent the best available estimate of the spillage emission
factor, so this value will be used in this analysis. The
remainder of the discussion will focus on the displacement
emission factor, but it should be noted that the emission
factor for spillage must be added to the displacement emission
factor in order to arrive at a total refueling emission factor.
2. Displacement Losses
As discussed earlier, there are three primary factors and
several secondary factors that determine the displacement
emission rate for refueling operations. The primary factors
are (1) the dispensed temperature (T0) of the gasoline (2)
the Reid Vapor Pressure (RVP) of the gasoline and (3) AT, or
the difference between the temperature of the residual gasoline
in the vehicle tank (Tt) and the dispensed temperature of the
gasoline used to refill the tank (ie. Tt-Td). To develop
emission factors for refueling operations, it will be necessary
to look at these parameters on a seasonal and national basis.
The most significant of the secondary factors are fuel tank
configuration differences, the effects of which have been
described in sections II and III above, and differences between
the RVP of the dispensed fuel and the residual fuel in the
tank, due to weathering of the tank fuel.
C. Calculation of Displacement Emission Factors
This section will derive nationwide average values for the
three major determinants, AT, T0, and RVP, from which the
uncontrolled displacement emission factors for several
scenarios will then be calculated.
1. Methodology
Overall, the methodology used in this process is to weight
the available regional temperature and RVP data by regional
highway fuel consumption to determine average national values

-------
-44-
for the appropriate time periods for each scenario to be
evaluated. These average values can then be used with the
multiple linear regression equation developed earlier to
calculate representative emission factors. The available data
indicate that there is a considerable amount of regional and
seasonal variation in the the temperature and RVP parameters,
making such a weighting process necessary. Also, the fuel
' consumption pattern is far from uniform throughout the U. S.
and the available data are not all aggregated at the same
levels. Fuel consumption and RVP data are available on a
monthly state-by-state basis while AT and T„ data are
available only on a monthly regional basis. The methodology
used to aggregate and weight these parameters will be discussed
following a brief description of the sources of the fuel
temperature, RVP and fuel consumption data that were used.
2. Sources of Data
. *• Fuel Temperature
Dispensed temperature and AT data used for calculating
emission factors are available from a 1975 gasoline temperature
survey conducted for the American Petroleum Institute (API) by
the Radian Corporation. [20] The year 1975 is considered to be
a representative year in terms of temperature, since the
average annual ambient temperature was within one degree of the
30 year mean. The study surveyed 56 U.S. gasoline stations
located in 22 cities; these were grouped into six geographic
regions. The six regions and the locations for the stations
surveyed are shown in Figure 29, and the monthly AT and T0
values from the survey are shown in Appendix B.
Not all of the stations reported data for all months of
the year, resulting in a few gaps in the data. The most
serious of these gaps occurred in the Pacific Northwest (region
6 in Figure 29) where AT data were reported only for the
month of May. Since the Pacific Northwest accounts for only
about 3.5 percent of the gasoline consumed for highway use in
the U.S., it was concluded that this region could be omitted
from the analysis without seriously affecting the accuracy of
the results. Alaska and Hawaii were also omitted from the
study, since no AT or T0 data were available from these
states. Other minor gaps of a month or so in AT and T0
data, primarily in the North Central U.S. and the Far West
(regions 4 & 5), were filled by points interpolated from the
existing data.

-------
- >
••
Survey sample stations

-------
-46-
b.	Nationwide Fuel Consumption
Nationwide fuel consumption (gasoline) by state was taken
from the 1983 version of the DOT/FHwA publication entitled
Highway Statistics - Table MF-26, This table contains
estimates of monthly gasoline consumption for each state and
the District of Columbia. Table MF-26 is shown in Appendix B.
To allow for further calculations, the monthly state fuel
consumption figures were summed for each region thus providing
monthly regional fuel consumption values.
c.	RVP
The RVP data were taken from 1983 ASTM maximum
specifications for the U.S.[21] The maximum specifications
were used rather than current actual levels on the assumption
that recent increases in RVP would continue and that by 1989
in-use RVP levels would be essentially at the maximum values
specified by. ASTM. This is already the case in some areas of
the country. The RVP values for each state and month are also
shown in Appendix B.
To get the RVP data on the same level of aggregation as
the temperature data, the state RVP data was divided into the
same regions as the temperature data and then consumption
weighted to get weighted RVP for each region in each month.
3. Air Quality and Health Effects Scenarios
To facilitate assessment of seasonal variation in the
emission rates, five seasonal air quality and health effects
scenarios were established and AT, T0, and RVP values were
calculated for each. The first scenario is simply the annual
average value for the nation or region. Two additional
six-month scenarios were chosen to represent warm weather
versus cold weather conditions. "Winter" is comprised of the
months October through March, while "Summer" consists of the
months April through September. Two additional scenarios were
chosen to represent the months in which most ozone violations
occur. These include a "Five Month" scenario (May through
September), and a "Two Month" scenario for the two peak ozone
violation months (July and August).
4. Consumption Weighting Calculation
In order to calculate national average AT, T0. and RVP
values for the five scenarios mentioned above, monthly regional

-------
-47-
data were consumption-weighted by the regional fuel consumption
values for' the months in question. As explained earlier,
monthly state RVP and fuel consumption values were aggregated
on the same monthly regional basis as the TD and AT data.
The generalized equation for calculating consumption weighted
values for each scenario is as follows:
n
I (ATr.„)(FCr,„)
AT= R,M=1	
FCt 9tn
Where R = region number from Figure 29
M = month number (of the seasonal scenario, not
necessarily of the calendar year)
n = number of months and number of regions evaluated in
a given scenario
AT*,n = temperature differential (AT) for region R
during month M
FCr.m = fuel consumption for region R during month M
FCto t ai = total national fuel consumption (less region
6, Alaska and Hawaii).
The key parameter shown in the equation above is AT. The
consumption weighted values for the other two key parameters
for any given scenario can be determined by substituting the
appropriate monthly T0 and RVP values in the equation above.
This can be done for each of the scenarios mentioned above to
get the appropriate values of the key parameters for use in the
refueling emission equation.
The results of these weighting calculations are shown in
Table 6. Regional and national average AT, T0 and RVP
information is presented for five scenarios: annual average,
summer, winter, five month ozone season and two month peak
ozone season. Regional fuel consumption values used in the the
weighting calculations and percentages of total fuel
consumption for each region are also shown for comparison
purposes. As explained above, Region 6 (Pacific Northwest) has
been omitted, as have Alaska and Hawaii. As would be expected,
To/ RVP and AT values vary both seasonally and from region
to region for any given season. Reasons for this variability
are discussed below.
As can be seen from the table, dispensed fuel temperatures
vary seasonally and from region to region. This is due largely
to climatic factors such as ambient temperature and" the amount
of solar radiation. Other relevant variables include the
volume and depth of the underground service station tanks,
layout of the fuel piping, composition of the surface over the
tanks and associated piping (e.g. concrete, asphalt, grass) and

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-48-
SCEmRIO:
Average Annual
Fuel Cansumpt.
(gal x 106)
% Tbtal
RVP (PSI)
A T CP)
td cp)
Suromer (Apr-Oct)
Fuel Consunpt.
(gal x 10®)
% Total
RVP (PSI)
AT (°F)
TD CP)
Winter (Oct-Har)
Fuel Consumpt.
(gal x 10®)
% Tbtal
RVP (PSI)
A T CP)
T0 CP)
liable 6
Weighted Temperature and RVP Parameters
REGION;
1	2	3	4	5
Nat'I Avg. N.Bast S.S^st S.Weat N.Cent. far W.
96,050.4
100.0
12.6
+4.4
68.9
51.846.3
100.0
11.5
+8.8
76.2
44.204.4
100.0
13.9
-0.8
60.3
41,658.5
43.4
13.3
+5.7
62.3
22,815.1
44.0
12.2
+10.7
70.7
18,843.5
42.6
14.6
—0.3
52.0
20,381.2
21.2
12.4
+4.0
81.8
10,689.0
20.6
11.4
+6.8
86.7
9,692.1
21.9
13.4
+0.9
76.4
11,977.6
12.5
11.4
+3.7
70.5
6,232.4
12.0
10.1
+7.6
78.6
5,745.3
13.0
12.8
-0.4
61.8
10,225.6
10.6
12.6
+5.5
66.2
5,690.2
11.0
11.2
+11.7
74.3
4,535.5
10.3
14.3
-2.4
56 ;1
11,807.6
12.3
11.7
+0.1
70.5
6,419.7
12.4
10.5
+3.9
77.2
5,388.0
12.2
13.3
-4.4
62.4

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-49-


1
2
3
4
5
Scenario
Nat11' Avg.
N.East
S.ESst
S.West
N.Cent.
Far W.
Ozone - 5 Mo.
(May-Sept)





Fuel Consumpt.
43,995.8
19,459.4
8,956.0
5,244.4
4,869.8
5,466.2
(gal x 106)






% Total
100.0
44.2
20.4
11.9
11.1
12.4
RVP (PSI)
11.3
12.0
11.2
9.9
10.9
10.3
4 T CF)
+9.4
+11.5
+7.5
+7.1
+12.1
+5.1
Td(#p)
78.8
73.8
88.0
80.8
79.0
79.0
Ozone - 2 Mo.
(Jul-Aug)





FViel Consuinpt.
18,664.7
8,326.2
3,760.0
2,147.7
2,103.0
2,327.8
(gal x 106)






% Total
100.0
44.6
20.1
11.5
11.3
12.5
RVP (PSI)
10.9
11.5
10.9
9.8
10.5
10.0
A T CP)
+9.9
+12.5
+8.2
+7.0
+13.3
+3.2
td Cf)
82,7
78.0
90.5
83.5
86.5
83.0

-------
-50-
protection from solar radiation for the tank system. Although
there is a strong correlation between ambient temperature
(Ta) and dispensed temperature, variation exists due to these
other factors. In general, the Radian study for API shows the
average dispensed temperature parallels the average ambient
temperature curve, with a positive offset (i.e., T0 is always
higher than T*). The amount of the offset varies seasonally
and regionally, undoubtedly due to climatic differences.
The RVP values shown in the table are ASTM maximum
recommended values. Figure 30 shows the average seasonal and
regional variation in these ASTM RVP values and the resulting
national averages for winter and summer. The regions by which
these data are aggregated are those shown in Figure 29. ASTM
assigns each state a "volatility class" and specifies maximum
recommended monthly RVP limits based on the climatic and
topographic factors. The five volatility classes are
designated A, i, C, D, and E, corresponding to maximum RVP
limits of 9, 10, 11.5, 13.5, and 15 psi, respectively. In
addition, a number of states have formally adopted RVP limits
similar to the ASTM recommended levels.[22] Particularly
noteworthy is California, where RVP is limited to 9 psi during
the months of the highest ozone concentrations in order to
decrease VOC emissions.
In-use RVP is essentially determined by the gasoline
refiners, subject to state laws and voluntary compliance with
the ASTM recommended limits. RVP varies seasonally as well as
regionally, based primarily on how the climate and topography
of an area affect vehicle operation. For example, RVP is
higher in the winter to assist in cold starting but decreases
in summer to avoid vehicle driveability problems such as vapor
lock. RVP values are generally higher for the northeastern
U.S. than the southeastern U.S. In general, for any given
season or area, RVP is higher as ambient temperature for any
given month decreases. The overall trend in in-use RVP has
been toward higher and higher values in recent years, due to
changes in vehicle design and gasoline refining practices,
leading to the conclusion that by 1990 the in-use values will
approximate the ASTM maximum limits.
The final factor, AT, also varies seasonally, with
positive values being more predominant in the summer and
negative values more prevalent in winter. Although there is a
certain amount of regional variation, the seasonal values are
very similar for all areas of the country.
There is also a certain amount of diurnal variation that
affects 4T values, which explains the presence of some

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SEASONAL RVP VALUES
ASTM MAXIMUM SPECIFICATIONS



%

%
m.
yV **
i

AVG ANN
IZZ] R1 (S3 R2
W NAT. AVG.
SUMMER
SEASONAL SCENARIOS
^ R3 ®
Figure 30
WINTER
KSI R5

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-52-
negative values in the suimner and positive values in the
winter. ¦ T0 is more stable than Tt due to the insulating
effect of the ground in which the service station storage tanks
are buried. Since vehicle tank temperatures follow ambient
temperatures more closely, the likelihood is strong that Tt
will be lower for those vehicles fueled in the morning,
resulting in negative, or at least less positive, AT
values. Conversely, diurnal heating would likely result in
higher Tt values in the afternoon, resulting in positive
ATs. The distance a car is driven before refueling also
affects Tt (Tt increases with distance driven, up to a
point) which in turn affects AT. Since these diurnal
effects are recurring and ongoing, one would expect the
differences between summer and winter ATs to be caused by
climatic and not diurnal variations.
5. Emission Rates
Given the weighted regional and national average TD,
AT and RVP values in Table 6 for each of the five scenarios
under consideration, we are now prepared to calculate the
emission rates for each of the scenarios and to assess how the
variation in the key parameters affects emission rates. These
emission rates for the different scenarios are calculated quite
simply by substituting the T0, AT and RVP values of Table 6
into the multiple linear regression relationship developed
earlier (given below) and solving for the emission rate (ER).
ER = -5.909 - 0.0949AT + 0.0884.To + 0.485 RVP
The results of these calculations for each of the five
scenarios are shown in Table 7. This emission rate data can be
compared regionally within each scenario and between the
various scenarios on a seasonal basis for each region' and
nationally.
Turning first to the regional evaluation within each
scenario, several points should be noted. First, overall, the
regional values for each scenario are relatively uniform given
the variation seen in the key parameters of Table 6. All
values fall within + 10 percent of the national average for
that scenario, with the exception of the southeastern U.S
(Region 2). In each of the five scenarios the emission rate
expected in the Southeast exceeds the national average for that
scenario by between 16 and 19 percent. The higher emission
rates in the southeastern US apparently occur because of the 10
to 16F° higher dispensed temperatures encountered there, as
compared to the national average. Simply by using the
coefficient for T0 in the emission rate equation, it can be

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-53-
Table 7
Displacement Emission Factors L/
REGIOWt
1	2	3	4	5
SCENARIO: Wat'1 Avq. S.East	S.East S.West N.Cent.	Far W.
Average Annual 5.9 5.5	7.0	5.5	5.5	6.0
Summer (Apr-Sep) 5.6 5.2	6.6	5.2	5.0	5.6
Winter (Oct-Mar) 6.2 5.8	7.2	5.8	6.2	6.5
02one-5 mo. (May-Sep) 5.6 5.3	6.6	5.4	5.2	5.6
Ozone-2 mo. (Jul-Aug) 5.7 5.4	6.6	5.6	5.6	6.0
Displacement losses only - a spillage factor must be added to derive a total
refueling emission factor.

-------
-54-
determined that the 10 to 16F° difference in T0 results in an
increase- of 0.9 to 1.4 g/gal in the emission for the various
scenarios. This easily accounts for the significantly higher
emission rate in the this region.
Climatological differences offer the most likely
explanation for the higher dispensed temperatures in the
Southeast. As explained earlier, the average TD value
generally follows the trend of the annual average ambient
temperature curve for any given region, but there is always a
positive offset (i.e., the T0 value is greater than the
average ambient temperature), probably because of solar heat
gain and the thermal storage effect of the ground, which in
turn are modified by the other factors noted above in section
C-4. The magnitude of the offset varies during the course of
the year for most regions, particularly where the ground may be
frozen during the winter months. In such areas T0 may
approach the ambient temperature in the Spring, when the
ambient temperature rises relatively quickly while the soil
temperature increases more gradually. The offset for the
Southeast, on the other hand, is relatively constant throughout
the year, likely because over most of the area the ground never
freezes and because of greater solar gains and higher ambient
temperatures, particularly during the Winter months.
Second, comparing the seasonal (summer and winter)
emission rates to the average annual rates for each region, all
the emission rates are within +10 percent of the average annual
value except for the North Central U.S. In this case the
seasonal variation is on the order of 12-13 percent, due to
slightly greater seasonal variation in the absolute values of
the key parameters. This relatively small seasonal variation
in the emission factors is likely due to the existence of
offsetting factors in the conditions that determine both Winter
and Summer emission rates. In the winter months, RVP's are
high and AT values tend to be more negative than during the
Summer. Both of these trends would tend to increase emissions,
but they are offset by lower dispensed temperatures, which tend
to decrease emissions. Conversely, during the Summer dispensed
temperatures are higher, which would increase emissions, but
the higher temperatures are offset by lower RVP's and positive
AT values, both of which tend to decrease emissions.
Third, comparing the two ozone scenarios to the average
annual scenario, the emission rates for all five regions and
the national average do not vary by more than 10 percent. In
this case the average annual values for each region exceed the
ozone scenario values in a range of 0 to about 6 percent. So
overall there is good agreement between the average annual

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-55-
emission rates and the emission rates expected in the ozone
prone months. This is true for all regions and on a national
level.
6. Effects of Fuel Weathering
In addition to the three primary factors discussed above,
fuel weathering also affects refueling emission rates. Fuel
tank weathering results in a difference in RVP between the
dispensed fuel and the residual fuel in the vehicle tank, with
fuel in the tank losing volatility due to the evaporation of
lighter ends in the gasoline, The very limited amount of
baseline testing that was done with lower RVP fuel in the
vehicle tank indicates that an increase in emissions, on the
order of a gram per gallon, resulted from an RVP difference of
approximately 1.9 psi between the tank and the dispensed fuel
(see Section III.C.). This general phenomenon was also
observed in the SRI study.[2] Unfortunately, neither the EPA
nor the SRI data are adequate to fully characterize the effect
of the RVP difference, although they do show the direction and
give a rough idea of the magnitude of the change.
In order to be able to include the effect of tank fuel
weathering in the emission rate calculation, one would also
need to know the average amount of in-use weathering that
occurs between refuelings, in addition to the effect of the
resultant difference in RVP values on the refueling emission
rate. This includes both the different vehicle and fuel
effects. Since neither of these variables can be determined
with any certainty at this time, the effect of tank weathering
has not been included in the emission factor calculation,
Although refueling emissions may thus be somewhat understated,
this effect may be partially offset by the method of RVP
determination for the calculation. Use of the ASTM maximum RVP
limits represents EPA's best judgment of future RVP levels.
However, if in-use RVP levels should be lower than these
maximum values, the resulting decrease in the emission factor
would tend to be at least partially offset by an increase in
refueling emissions due to fuel weathering.
D. Conclusions
At the beginning of this investigation it was felt that it
might be necessary to develop both a seasonal emission factor
for air quality calculations and an average annual emission
factor for health exposure risk calculations. However, the
relative uniformity of the seasonal emission factors indicates
that the average annual values can be used for both purposes
without introducing any significant error into the air quality

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-56-
calculations. If only air quality calculations were involved,
it might be more appropriate to use only a summer emission
factor, although by so doing two important "by-products" of the
air quality calculation, the emissions inventory calculation
and the calculated lifetime emissions reduction per vehicle,
would both be understated. An annual average would be more
appropriate for these latter two purposes as well as for health
exposure risk calculations.
On the other hand, use of an average annual emission rate
for air quality determinations may theoretically overstate the
air quality benefits somewhat. The difference between the
summer and average annual emission factors is relatively small
(less than 5 percent), however, and any differences in air
quality calculations, i.e. SMSAs brought into compliance or
percent change in air quality, would likely disappear in the
roundoff of the EKMA model. Thus in practical terms, it would
likely be very difficult to see any differences in the air
quality outputs resulting from the use of the average annual
values, whereas there are. real advantages to its use in terms
of emissions inventory, lifetime emissions and cost-
effectiveness calculations.
Finally, it does not appear that there will be a need for
seasonal emission factors for health effects purpose as a
result of changes in the amount of benzene and other
potentially hazardous species in the total VOC emitted. Such
emissions are a function of the percentage of the hazardous
pollutant present in liquid gasoline and the same temperature
considerations that affect the basic VOC emission rate. In
order to have significant seasonal variation in the emissions
of these hazardous species, then, either the seasonal
percentage of these species in the liquid gasoline would have
to vary significantly or, since such emissions are normally
expressed as a percentage of total VOC emissions, winter and
summer VOC emission factors would have to differ significantly
from the annual average. As stated above, the latter condition
is not the case. Correspondingly, the 1983/84 NIPER gasoline
surveys show no significant difference between the winter and
summer benzene percentages in liquid gasoline. For these
surveys average summer and winter benzene fractions in the
liquid gasoline averaged about 1.3 percent.[23,24] Similar
data are not available for other potentially hazardous species,
but there is no reason to believe that the liquid fraction of
these species varies regionally or seasonally. Therefore it is
reasonable to conclude that seasonal differences in the
emission factors will not necessitate separate emission factors
for either health effects or air quality purposes.

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-57-
For these reasons, it was decided to use the average
annual displacement value of 5.9 grams per gallon for all
calculations. Adding 0.3 grams per gallon for spillage results
in a national average refueling emission factor of 6.2 grams
per gallon.

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Appendix A
BASELINE TEST RESULTS

-------
1983 Oidsmooile Cutlass Supreme
Dispensed Temperature = 828F 3 KVPs









Disp.
Heat



Disp.
Losses
Liq.
Vap.
Disp.
tosses
Time
Time
Test
KVP
TCF)
Temp('F)
(gm/gal)
Temp('F)
TempC'F)
Gals
(g®s)
(min.}
(min.)
845638
9.0
1.5
80.5
5.209
82.0
83.0
14.8
77.1
2.52
28.00
845639
9.0
0.
82.0
5.456
82.0
83.0
14.7
80.2
2.53
24.00
845637
9.0
10.8
82.0
5.021
92.8
93.9
14.6
73.3
2.58
52.00
845632
9.0
8.1
83.9
5.308
92.0
92.5
14.6
77.5
2.67
50.00
845636
9.0
22.0
81.0
4.407
103.0
102.0
15.0
66.1
2.63
36.00
845631
9.0
18.5
83.5
4.632
102.0
100.5
15.5
71.8
2.70
37.00
845628
9.0
36.7
82.3
3.115
119.0
116.0
14.8
46.1
3.00
74.00
845630
9.0
37.0
82.0
2.918
119.0
117.0
14.6
42.6
2.58
67.00
850113
9.0
12.0
80.5
4.934
92.5
92.3
15.1
74.5
1.97
42.00
850114
9.0
7.7
83.3
4.934
91.0
93.0
15.1
74.5
1.98
32.00
850115
9.0
12.3
80.0
4.331
92.3
93.4
15.1
65.4
1.98
30.00
850117
9.0
11.9
79.8
5.126
91.7
90.5
15.1
77.4
2.02
48.00
851354
9.0
2.3
81.7
5.060
84.0
82.5
15.0
75.9
1.98
28.00
851355
9.0
1.5
81.5
5.133
83.0
82.5
15.0
77.0
1.97
32.00
845950
11.9
-1.1
81.0
7.831
79.9
82.5
14.8
115.9
3.30
24.00
845951
11.9
-.8
83.0
8.074
82.2
83.0
14.8
119.5
3.42
24.00
845945
11.9
11.0
81.0
6.490
92.0
92.3
14.7
95.4
3.25
60.00
845947
11.9
10.0
83.2
6.133
93.2
92.5
15.0
92.0
3.33
46.00
850057
11.9
10.0
82.0
6.395
92.0
93.0
15.2
97.2
1.98
46.00
850104
11.9
11.1
80.8
5.947
91.9
93.0
15.0
89.2
2.00
45.00
845943
11.9
17.0
85.0
4.842
102.0
102.0
14.6
70.7
3.35
35.00
845944
11.9
21.7
80.8
4.432
102.5
102.0
14.8
65.6
3.13
40.00
845946
11.9
20.5
83.0
5.743
103.5
103.0
14.8
85.0
3.33
37.00
850105
11.9
17.2
83.8
5.327
101.0
102.5
15.0
79.9
2.05
39.00
850106
11.9
18.0
81.8
5.007
99.8
98.5
14.9
74.6
1.97
39.00
845941
11.9
34.0
86.0
3.830
120.0
118.3
15.3
58.6
3.50
68.00
845942
U .9
39.5
82.0
3.500
121.5
118.0
14.6
51.1
3.27
51.00
845948
11.9
38.8
81.2
3.514
120.0
118.5
14.8
52.0
3.23
72.00
845642
12.6
-2.0
82.5
8.938
80.5
83.0
14.5
129.6
3.62
25.00
845641
12.6
7.5
. 84.0
7.366
91.5
92.5
14.5
106.8
3.58
48.00
845627
12.6
8.2
84.0
6.892
92.2
92.5
14.8
102.0
3.83
60.00
845294
12.6
16.6
84.0
6.290
100.6
102.0
14.5
91.2
3.68
39.00
845625
12.6
19.0
81.0"
6.081
100.0
101.0
14.9
90.6
3.38
41.00



Dispensed Temperature
= 92'F 3 KVPs




845289
9.0
-11.0
91.0
6.952
80.0
81.8
14.5
100.8
2.88
26.00
845290
9.0
8.3
92.0
6.324
100.3
101.0
14.2
89.8
2.95
38.00
845280
9.0
29.0
91.0
4.257
120.0
119.0
14.8
63.0
2.78
67 .00
845292
9.0
27.8
91.2
4.097
119.0
116.0
14.5
59.4
2.82
67.00
850110
9.0
1.5 .
90.5
6.470
92.0
92.5
14.9
96.4
2.05
34.00
850111
9.0
1.5
90.5
6.831
92.0
93.5
15.4
105.2
2.07
34.00
850112
9.0
2.2
90.0
5.887
92.2
94.2
15.1
88.9
2.00
36.00
851356
9.0
15.2
88.0
4.700
103.2
100.0
15.0
70.5
2.00
44.00
851357
9.0
8.4
92.0
6.060
100.4
97.0
15.1
91.5
2.05
32.00

-------
845931
11.9
-10.5
92.0
10.250
845932
11.9
-10.3
91.3
11.431
845935
11.9
2.0
90.0
8.307
845937
11.9
1.0'
91.0
7.270
850054
11.9
2.5
90.5
10.060
850053
11.9
-1.0
93.0
9.765
845938
11.9
9.5
92.0
8.066
845939
11.9
10.1
91.8
7.815
845933
11.9
22.1
92.0
4.921
845936
11.9
30.6
90.9
3.311
850055
11.9
25.9
93.0
4.066
850056
11.9
28.8
91.2
4.821
845956
10.0
-11.0
91.0
8.597
845957
10.0
-10.0
90.0
8.128
845954
10.0
1.8
90.2
6.966
845955
10.0
2.0
90.0
7.240
845953
10.0
11.8
90.8
6.479
81.5
81.0
92.0
92.0
93.0
92.0
101.5
101.9
114.1
121.5
118.9
120.0
80.0
80.0
92.0
92.0
102.6
81.5
15.2
155.8
4.52
32.00
83.0
15.3
174.9
4.53
24.00
91.5
15.0
124.6
3.98
46.00
93.0
15.2
110.5
3.77
53.00
90.8
14.9
149.9
3.08
40.00
92.0
15.3
149.4
3.28
42.00
102.5
15.2
122.6
4.22
40.00
103.0
15.1
118.0
4.22
39.00
109.9
15.1
74.3
4.05
67.00
119.0
14.8
49.0
3.60
65.00
117.8
15.2
61.8
2.55
49.00
117.2
15.1
72.8
2.32
58.00
82.3
14.9
128.1
3.48
21.00
83.0
14.9
121.1
3.43
24.00
93.0
14.8
103.1
3.33
48.00
92.3
15.0
108.6
3.42
48.00
102.0
14.6
94.6
3.33
35.00
Single Blanket Ettta
845107
9.0
-10.8
90.8
6.353
80.0
78.0
15.0
95.3
2.85
36.00
845276
9.0
-11.0
90.0
6.651
79.0
76.0
14.6
97.1
2.83
42.00
845102
9.0
2.0
90.0
5.980
92.0
86.5
15.0
89.7
2.93
96.00
845103
9.0
-1.0
92.7
6.153
91.7
86.0
15.0
92.3
2.97
178.00
845109
9.0
-3.2
93.2
6.554
90.0
84.0
14.8
97.0
2.93
74.00
845105
9.0
7.1
91.6
5.027
98.7
95.6
15.0
75.4
2.93
212.00
845106
9.0
8.0
91.5
5.060
99.5
96.4
14.9
75.4
2.80
173.00
845275
9.0
27.5
92.5
3.453
120.0
114.0
15.0
51.8
2.87
306.00




Road
Prep Data





845286
9.0
10.5
92.5
4.815
103.0
105.9
14.6
70.3
-
182.00
845287
9.0
-3.5
92.0
6.060
88.5
90.0
13.4
81.2
2.60
172.00
845961
10.0
-6.0
92.0
7.985
86.0
87.5
13.5
107.8
3.15
185.00
845959
10.0
-3.9
91.6
6.514
87.7
88.7
14.2
92.5
3.22
159.00



Dispensed Fuel HVP *
11.9 *anK
Fuel RVP
= 10.0



850904
11.9
0.0
92.0
9.566
92.0
88.0
14.5
138.7
2.27
16.00
850913
11.9
3.1
90.8
8.731
93.9
90.3
14.5
126.6
2.25
19.00



Large Vapor-Liquid Temperature Differences



850885
11.9
3.2
90.8
8.220
94.0
86.8
15.0
123.3
2.07
16.00
850887
11.9
3.0
91.0
8.140
94.0
87.0
15.0
122.1
2.10
16.00
850901
11.9
4.7
89.0
8.947
93.7
104.0
15.0
134.2
2.10
36.00
850902
11.9
4.0
89.0
9.093
93.0
102.5
15.0
136.4
2.07
34.00

-------
1984 Ford Escort


-
Dispensed Temperature
= 809 F 2 KVPs




851161
9.0
3.7
80.0
4.456
83.7
83.0
10.3
45.9
4.46
17.00
851162
9.0
4.0
79.0
4.308
83.0
83.0
10.4
44.8
1.37
16.00
851163
9.0
9.3
80.7
4.269
90.0
91.9
10.4
44.4
1.37
28.00
851165
9.0
12.5
81.0
4.574
93.5
92.5
10.8
49.4
1.43
32.00
851164
9.0
21.2
80.3
4.221
101.5
101.8
10.4
43.9
1.43
40.00
851166
9.0
22.5
78.5
3.159
101.0
102.5
10.7
33.8
1.42
44.00
851213
9.0
10.5
81.0
4.673
91.5
91.7
10.4
48.6
1.37
28.00
851214
9.0
20.5
80.5
4.346
101.0
101.0
10.4
45.2
1.35
42.00
850304
11.9
1.5
81.2
6.091
82.7
84.0
11.0
67.0
1.47
25.00
850012
U.9
12.0
80.0
5.750
92.0
94.0
10.8
62.1
1.42
57.00
850014
11.9
12.7
80.3
5.606
93.0
94.0
10.9
61.1
1.43
56.00
850311
11.9
2.7
80.0
5.595
82.7
82.3
U.l
62.1
1.45
32.00
850314
11.9
11.8
81.2
5.694
93.0
92.7
11.1
63.2
1.45
50.00
850312
11.9
11.1
81.0
5.654
92.1
92.2
10.7
60.5
1.40
52.00
850313
11.9
13.4
79.1
5.455
92.5
91.8
11.2
61.1
1.47
58.00
850013
11.9
3.7
80.0
6.255
83.7
83.9
11.0
68.3
1.43
24.00
850303
11.9
3.7
80.0
5.991
83.7
84.0
11.6
69.5
1.45
25.00
850011
11.9
13.3
79.6
5.890
92.9
93.0
10.9
64.2
1.45
50.00
850310
U.9
4.5
78.5
6.279
83.0
83.7
10.4
65.3
1.38
28.00
850309
U.9
12.0
80.5
6.077
92.5
95.0
10.4
63.2
1.43
45.00
850307
U.9
22.0
80.5
5.390
102.5
103.0
10.5
56.6
1.43
40.00
850308
U.9
23.0
80.0
5.202
103.0
105.0
10.4
54.1
1.40
38.00
851160
U.9
20.2
80.0
5.567
100.2
102.0
10.4
57.9
1.38
42.00



Dispensed Temperature
= 90°F 2 RV?3




851167
9.0
8.9
85.0
4.740
93.9
94.5
10.4
49.3
1.40
32.00
851168
9.0
4.5
89.5
5.221
94.0
93.2
10.4
54.3
1.42
30.00
851169
9.0
4.8
89.7
5.115
94.5
91.0
10.4
53.2
1.38
32.00
851211
9.0
6.0
89.0
4.875
95.0
96.0
10.4
50.7
1.38
30.00
846446
U.9
2.0
92.5
7.903
94.5
98.2
11.3
89.3
1.63
26.00
846447
U.9
.7
92.3
7.228
93.0
98.0
11.4
82.4
1.63
21.00




Dispensed
Temperature = 66°F




350305
U.9
7.5
66.5
5.029
74.0
73.9
10.5
52.8
1.35
6.00
850306
U.9
5.0
*67.5
5.286
72.5
72.0
10.5
55.5
1.37
5.00

-------
1983 Plymouth Reliant
851151
11.9
2.5.
80.0
6.265
82.5
84.3
9.8
61.4
1.32
16.00
851150
11.9
1.7
81.8
6.640
83.5
84.0
10.0
66.4
1.32
16.00
851152
11.9
10.0
81.0
6.439
91.0
89.0
9.8
63.1
1.30
32.00
851153
11.9
19.3
80.0
4.969
99.3
97.5
9.6
47.7
1.28
44.00
851154
11.9
14.1
79.9
5.316
94.0
94.0
9.5
50.5
1.48
32.00
851155
11.9
18.0
81.0
6.109
99.0
99.7
10.1
61.7
1.37
38.00
845486
9.0
1.5
90.5
5.577
92.0
86.5
10.4
58.0
1.92
38.00
845487
9.0
-1.5
91.5
• 5.677
90.0
87.0
9.9
56.2
1.87
38.00
845492
11.9
3.0
89.0
6.839
92.0
88.3
11.2
76.6
3.12
42.00
845493
11.9
1.3
91.0
7.036
92.3
89.5
U.2
78.8
3.17
43.00
851157
9.0
4.3
68.0
3.763
72.3
73.2
9.7
36.5
1.30
6.00
851156
9.0
4.0
69.0
3.939
73.0
72.0
9.8
38.6
1.32
4.00
851159
11.9
5.5
68.0
5.299
73.5
77.5
9.7
51.4
1.28
12.00
851246
11.9
5.6
68.3
5.323
73.9
78.0
9.9
52.7
1.30
14.00




1983
Buick Skylark




846410
11.9
2.7
90.5
7.925
93.2
92.2
13.4
106.2
3.75
28.00
846413
11.9
13.0
85.0
6.471
98.0
91.0
13.6
88.0
2.32
28.00
846454
11.9
-.9
94.3
7.540
93.4
91.9
13.7
103.3
2.15
26.00
846453
11.9
-2.0
93.5
7.353
91.5
90.0
13.6
100.0
2.05
23.00
846412
11.9
.5
92.0
7.365
92.5
90.6
13.7
100.9
2.05
20.00
846452
11.9
.5
92.0
7.708
92.5
94.3
12.0
92.5
1.80
19.00




1984 Chevrolet Celebrity




850205
11.9
12.7
80.0
4.632
92.7
92.2
13.6
63.0
1.78
44.00
850209
11.9
10.7
81.0
4.596
91.7
92.0
13.6
62.5
1.78
38.00
850208
11.9
13.2
78.8
4.706
92.0
92.1
13.6
64.0
1.85
40.00
850207
11.9
.7
91.8
6.333
92.5
96.0
13.8
87.4
1.95
58.00
850206
11.9
-.5
92.5
6.876
92.0
94.5
13.7
94.2
1.95
38.00
850204
11.9
2.6
89.4
6.080
92.0
94.0
13.8
83.9
1.93
36.00




1983 LOT Crown Victoria




850400
11.9
11.2
80.8
7.448
92.0
95.0
15.4
114.7
2.02
53.00
850401
11.9
U .8
79.2
7.200
91.0
94.0
14.5
104.4
1.90
51.00
850402
11.9
U.O
80.5
7.558
91.5
94.2
15.4
116.4
2.05
42.00
850404
11.9
1.0
90.8
11.166
91.8
95.4
15.7
175.3
2.30
34.00
850405
11.9
1.8
90.0
10.500
91.8
94.2
15.6
163.8
2.25
36.00




1979 Chevrolet 3/4 Ton
Pickup




850689
11.9
14.5
81.7
6.048
96.2
92.0
16.6
100.4
2.33
32.00
850690
11.9
13.2
82.3
5.813
95.5
93.0
16.6
96.5
2.27
28.00
850691
11.9
10.3
82.3
5.795
92.6
93.5
16.6
96.2
2.30
28.0C
850686
11.9
-.1
91.3
7.916
91.7
93.2
16.7
132.2
2.43
38.0C
850688
11.9
2.6
89.7
7.964
92.3
93.5
16.6
132.2
2.58
32. OC

-------
1979 Dodge Truck W150
850990
11.9
12.5
80.0
850991
11.9
12.0
80.0
850987
11.9
2.1
91.7
850988
11.9
.2
91.8
6.593
92.5
94.0
6.456
92.0
92.7
8.984
93.8
95.0
8.950
92.0
91.8
18.2
120.0
2.47
46.00
18.0
116.2
2.38
42.00
18.3
164.4
3.30
30.00
18.0
161.1
2.78
40.00

-------
Appendix B
Fuel Consumption Weighting Data

-------
HI6HMAY USE OF 8A80LWE BY MONTHS - IMS*
run 988 !M CMIMM IIU
h ii «Mifsis it Mmt-fsti
mil W'ti
1884
S?At«
VU Mfl
M
MUM* SI
IIS cisvs
HI
•At MM)
y
iMti
nrfSMMS
IMS
AIU
118*4
ItlAilAX
II
It
».»
itt.ysi
ii.iii
III.ISS
81,881
ttv.sss
IIMII
ss,its
MI.MI
ll.ltl
114,984
81,194
t««,svs
I*.IIS
198,ISS
St.its
188,88*
II,Sit
lll.lll
iM.m
lll.lll
IS,III
IIS.SIS
II.IM
188,888
S.MS
ifi.srt
111,114
191.491
•l,*9*
ui.m
149,141
isi.sis
is.sis
I9I.IH
S*.ilS
I4I.SII
8.418
lit.it*
St,914
148.881
IS.SSS
lll.lll
*!,9I|
181.84!
11.111
IIS.SM
SI.IS*
I.818.448
181.848
i.svs.*s*
1.8*4,881
•s.ssi
•IS.MI
fS.SSI
*8,888
4KMII*
XWAM
miuicvf
IUMM
I
II
I*
II
IS*.11V
•4.411
tlMll
11,111
IS.ITS
818,188
118,198
8*,*89
II.Ill
SSI,lit
lll.lll
III.
11,111
814,848
111,111
111.911
9*.141
•It ,111
114.VII
111,III
11,111
1,899,899
111,111
111,114
11.118
I,ISf.ISS
111.>14
184,888
*9.rs*
sis ,%>i
IU,«I4
111,111
19.888
Sit.Ill
111,141
111,144
14,114
SIS,ISS
144.(St
14.444
11.411
848.189
SS.III
14,411
14,141
IS.SS4.4S9
1,888.848
1,999.Ml
•*4.1*9
•14.1*4
IS.fSI
ifT. m est.
IS8ISA
(66(14
ill
14 .4
8.9
It
II
II-141.
111.SIS
IIS.441
II,ISS
11,114
1*4.111
lll.lll
11,111
18,448
411.Ml
til.Ill
IS.SSI
11,141
411,914
tit.114
94,444
14.4*1
444,IIS
ISS.IIS
14.MS
14,111
111,141
141.111
14,III
(l,l»l
411,444
III.4*9
II.Ml
(4.441
4IS.9SI
m.irs
18.I8*
• 4, 449
111,411
<11.411
IS,SSI
14,144
4SI,S44
114.41*
11,111
11,114
IIS.Ill
tts.su
14,918
11,191
441,141
I4I.44S
14,191
1SS.848
4.ISS.SIS
1.811,111
mass
~944
ISf,SI I
SS.941
144
1114014
IS8IAAA
14.1
II
II. I
II
94,141
144,111
111.441
11.141
14,441
194,114
141,1*4
II .III
141,111
111.944
I St. Ml
11,141
141.111
111,111
ISS.SSS
19.|9S
414,119
•98,848
114.MI
IS,SSI
444,191
191.111
IIS,IS!
41,III
414.(41
141,141
111,114
44.411
419,911
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-58-
References
1.	"An Experimental Study of Vehicle Refueling
Emissions," Albert M. Hochhauser and Raymond J. Campion, SAE
Paper No. 760307, Feb. 1976.
2.	"Testing of a Vapor Balance Service Station Vapor
Control System by the California ARB Test Procedure — BREA
June 1976," Technical Memorandum from M.J. Dougherty to Mr.
Cloyd P. Reeg, Research Department, Union Oil Company of
California, August 19, 1976.
3.	"Expansion of Investigation of Passenger Car
Refueling Losses," EPA-460/3-76-006 U.S. EPA, OAWM, OMSAPC,
ECTD, September 1975.
4.	"Healy Phase II Vapor Recovery System Certification
Report," Scott Environmental Technology, June 1982.
5.	"A Service Station Test of a Vapor Balance System
for the Control of Vehicle Refueling Emissions," A.M.
Hochhauser and L.S. Bernstein, Exxon Research and Engineering
Company, July 1, 1976.
6.	"Evaluation of Test Procedures for Measuring Vehicle
Refueling Emissions," API Publication No. 4276, July 8, 1976.
7.	"Service Station Vapor Recovery: Vapor Balance
System Performance Diamond Bar, California, March 5-12, 1974,"
Atlantic Richfield Company, Products Division, Research and
Engineering, April 3, 1974.
8.	"Vapor Recovery Nozzle Development and Field
Testing," B.E. • Weidenaar, H.J. Grimes, and R.G. Jewell, SAE
Paper No. 741038, October 1974.
9.	"A Study of Variables that Effect the Amount of
Vapor Emitted During the Refueling of Automobiles," API Report
CEA-21, May 16, 1975.
10.	"Vapor Control Efficiency of Simple Displacement
Systems at Two Service Stations," Technical Memorandum from
M.J. Dougherty, Research Department, Union Oil Company of
California, September 22, 1975.
11.	"Air Pollution Emission Test: Emissions from
Gasoline Marketing Operations at Exxon Retail Station, Hayward,
California," U.S. EPA, OAWM, OAQPS, EMB, April 1975.

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-59-
12.	"Air Pollution Emission Test: Emissions from
Gasoline Marketing Operations at Standard Oil of California
Retail Station, Davis, California," U.S. EPA, OAWM, OAQPS, EMB,
May 1975.
13.	"On-Board Control of Vehicle Refueling Emissions:
Demonstration of Feasibility," API Publication No. 4306,
October 1978.
14.	"Vapor Control Concepts," M.W. Lieferman, in
"Vehicle Refueling Emissions Seminar," API Publication No.
4222, December 1973.
15.	"A Chronic Inhalation Study With Unleaded Gasoline
Vapor," Journal of the American College of Toxicology, American
Petroleum Institute, 1984.
16.	"Compilation of Air Pollutant Emission Factors,"
(AP-42), U. S. EPA, OAWM, OAQPS, 1977.
17.	"Investigation of Passenger Car Refueling Losses,"
APTD-1453, Scott Research Labs for EPA and CRC, September, 1972.
18.	"Utility of Reactivity Criteria in Organic Emission
Control Strategies for Los Angeles," Final Report, EPA Contract
No. 68-02-1735, December, 1975.
19.	"Phase II Vapor Recovery Evaluation Program," South
Coast Air Quality Management District, c.1980.
20.	"Summary and Analysis of Daca From Gasoline
Temperature Survey Conducted at Service Stations by API" (API
Publication No. 4278), Radian Corporation, 1976.
21.	"Standard D439-83," Annual Book of ASTM Standards,
Part 23, American Society for Testing and Materials, 1983.
22.	"Digest of State Inspection Laws - Petroleum
Products," Fourth Edition, API Publication 926, 1985.
23.	"Motor' Gasolines, Winter 1983-84" (NIPER-135 PPS
84/3), U.S. DOE, National Institute for Petroleum and Energy
Research (NIPER), June, 1984.
24. "Motor Gasolines, Summer 1984" (NIPER-138 PPS 85/1),
U.S. DOE, NIPER, February, 1985.

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