Summary and Analysis of Comments
on the
Notice of Proposed Rulemaking
for
Emission Standards and Test Procedures
for Natural Gas-Fueled and Liquefied
Petroleum Gas-Fueled Vehicles and Engines,
and
Certification Procedures for Aftermarket
Conversion Systems
May 1994
Engine and Vehicle Regulations Branch
Regulation Development and Support Division
Office of Mobile Sources
Office of Air and Radiation
U S. Environmental Protection Agency

-------
Summary and Analysis of Comments
Emission Standards and Test Procedures
for Natural Gas-Fueled and Liquefied
Petroleum Gas-Fueled Vehicles and Engines,
and
Certification Procedures for Aftermarket
Conversion Systems
on the
Notice of Proposed Rulemaking
for
Table of Contents
Page
I. Introduction
2
EI. Natural Gas Fuel Specifications
6
in Lead Time
8
IV Small Volume Procedures for Aftermarket Conversions
10
V. Refueling Standards
A. Natural Gas
11
B. Liquefied Petroleum Gas
13
1

-------
I. Introduction
On November 5, 1992 EPA published a Notice of Proposed Rulemaking (NPRM) which
put forth proposed emission standards and test procedures for natural gas-fueled and liquefied
petroleum gas-fueled motor vehicles and engines. In that notice the Agency proposed that the
emission standards for these vehicles, collectively referred to as gaseous-fueled vehicles, be
largely the same as emission standards which apply to other, currently regulated vehicles. These
standards were proposed at the request of industry in order to remove the potential barrier that
the lack of such standards may present to the widespread introduction of gaseous-fueled vehicles
into the marketplace
In addition to emissions standards and test procedures for new gaseous-fueled vehicles,
the proposal also contained procedures by which one can secure an exemption from the Clean
Air Act tampering prohibition for an aftermarket conversion (i e., a vehicle modification which
allows the vehicle to operate on a fuel other the fuel it was designed and certified to operate on).
These procedures, based on the current new vehicle certification procedures, were intended to
clarify how one can avoid application of the EPA tampering policy on a conversion by providing
a method of demonstrating that a vehicle will continue to meet applicable emission standards
after the conversion.
EPA held a public hearing on the NPRM in Ann Arbor, Michigan on December 3, 1992.
At that hearing oral comments to the NPRM were received and recorded. A written comment
period remained open following the hearing until January 15, 1993. A complete list of
organizations which provided comments on the NPRM is contained in Table 1. Common
abbreviations for the organization names are also listed.
All of the significant comments to the NPRM are addressed in the preamble to the final
rule. This summary and analysis of comments document is intended to address several areas in
more detail than in the preamble. The interested reader is urged to consult the preamble to this
rule for a discussion of all issues raised by commenters.
2

-------
Table 1
List of Commenters
to the NPRM
Commenter
Mountain Fuel Supply Company
LP Gas Clean Fuels Coalition
Engine Manufacturers Association
Detroit Diesel Corporation
Cummins Engine Company
EMPCO
Mesa Technologies
American Gas Association and
Natural Gas Vehicle Coalition
American Automobile Manufacturers Association
Chrysler Corporation
National Propane Gas Association
Stewart & Stevenson Power Company
Southern California Gas Company
Sherex Industries
San Luis Butane
Federal Express Corporation
American Methanol Institute
Abbreviation
EMA
DDC
AGA/
NGVC
AAMA
NPGA
SoCal Gas
AMI
3

-------
Table 1 - continued
List of Commenters
to the NPRM
Commenter
National Association of Fleet Administrators
Manufacturers of Emission Controls Association
Navistar International Transportation Corporation
New York City Department of Environmental Protection
U S Small Business Administration
Beacon Power Systems Incorporated
Econogas Fleet Systems
Caterpillar Incorporated
Carburetion and Turbo Systems Incorporated
Baltimore Gas and Electric Company
Specialty Equipment Marketers Association
General Motors Corporation
Colorado Department of Health
Amoco Corporation
Montana-Dakota Utilities Company
Columbia Gas Distribution Companies
California Energy Commission
Abbreviation
NAFA
MECA
NYCDEP
SBA
BG&E
SEMA
GM
CDH
CEC
4

-------
Commenter	
Phillips 66 Company
Southwest Research Institute
Table 1 - continued
List of Commenters
to the NPRM
Abbreviation
SwRI
5

-------
II.
Natural Gas Fuel Specifications
Summary of the proposal: It is the Agency's belief that certification test fuels should resemble
the fuels that a vehicle is likely to encounter in-use. Given the wide range of natural gas
compositions currently available throughout the United States, the Agency proposed very broad
specifications for natural gas certification fuel. These specifications included a range for methane
content of 74 to 98.5 percent, as well as broad ranges for several other parameters. The proposed
specifications were based on a Gas Research Institute (GRI) report on the variability of natural
gas composition throughout the United States.' The 74 to 98.5 percent methane specification
encompassed all natural gas surveyed, excluding the small amounts of propane-air peakshaving
gases.
Summary of the comments: Although the Agency received some comments in support of its
proposed natural gas certification fuel specifications, in general commenters believed that the
proposed specifications were much too broad. The comments in favor of tighter specifications
fell into two general categories. First, several commenters stated that they agreed with EPA's
general approach of a broadly defined specification in order that certification fuel be
representative of in-use fuel. These commenters, however, felt that the proposed fuel
specification was much too broad and encompassed fuels which could not be considered
representative of most natural gas. Other commenters felt that, in order to be able to
meaningfully compare results from different tests, a very narrowly defined test fuel specification
is needed. Most of these commenters recommended that EPA adopt the California Air Resources
Board (CARB) certification fuel (90% methane, ± 1%, among other requirements) as the federal
certification fuel, pointing out the cost savings associated with having only one certification fuel
for both federal and California certification testing. AGA/NGVC and AAMA suggested that EPA
adopt a narrower range of specifications based on the CARB specifications. Such an approach
would use the lower methane limit (89%) of the CARB certification fuel in conjunction with
CARB's upper limits on all of the other components (ethane, Cj+, etc.).
EPA response to comments: The Agency both understands and sees the merits in the arguments
for tighter natural gas certification fuel specifications. However, as was previously stated, EPA
also believes it is important that certification fuel be representative of in-use fuel. Thus, in
developing today's final rule the Agency has attempted to find a middle ground between these
seemingly conflicting needs. The Agency believes the approach suggested by AGA/NGVC and
AAMA strikes a good balance between the need for a tightly defined certification fuel and the
conflicting desire that the certification fuel represent the variability of in-use fuel. The approach
suggested by AGA/NGVC and AAMA yields the specifications shown in the following table.
1 "Variability of Natural Gas Composition in Select Major Metropolitan Areas of the
United States", GRI-92/0123, Gas Research Institute, March, 1992.
6

-------
Natural Gas Certification Fuel Specifications
Item

ASTM test method
No.
Value
Methane
min. mole pet.
D1945
89.0
Ethane
max. mole pet.
D1945
4.5
C3 and higher
max. mole pet.
D1945
2.3
C6 and higher
max. mole pet.
D1945
0.2
Oxygen
max. mole pet.
D1945
0.6
Inert gases: Sum
of C02 and N2
max. mole pet.
D1945
4.0
Odorant*



The natural gas at ambient conditions must have a distinctive odor potent enough for its presence
to be detected down to a concentration in air of not over 1/5 (one-fifth) of the lower limit of flammability.
The Agency believes these natural gas certification fuel specifications are fairly
representative of in-use natural gas. Based on the GRI report, the minimum 89% methane
specification encompasses over 90% of in-use natural gas. Although there are many measures
of natural gas quality, the methane content is a parameter which is generally used to describe
natural gas quality. It is assumed that lower methane content signifies lower quality natural gas
due to the higher nonmethane content. However, in low altitude areas the methane content
seldom goes two to three percent below the 89 percent level in the certification fuel specification.
Almost all of the gas not covered by this specification (i.e., gas with a methane content
below 89 percent) is sold in high altitude areas where some gas contains higher levels of inert
gases than that sold at low altitudes. Thus, while the natural gas in high altitude areas can have
lower methane content than in low altitude areas (down to 74 percent, as in the NPRM), it does
not have a significantly higher methane to nonmethane HC ratio. The Agency believes that
excluding high altitude gas from the test fuel specifications should not present a problem for
vehicles which are certified using the 89 percent minimum methane certification fuel but are
operated at high altitudes because, in general, vehicles which will be certified under the
provisions of today's rule are expected to utilize electronic feedback control systems for proper
management of the fuel/air ratio. The Agency believes that these systems will be able to account
for any differences in fuel composition between high altitude natural gas and natural gas in the
rest of the country.
7

-------
It should be noted that, while the natural gas certification fuel specifications contained in
today's rule are much broader than CARB's, CARB certification fuel does fall within the federal
specifications, and thus could be used for federal certification testing.
in. Lead Time
Summary of the proposal: As was stated in the NPRM, the Agency believes that the standards
are not technology-forcing, and that they could be met largely through currently available
technology. Thus, the only lead time requirement for meeting the proposed standards would be
that of actually going through the certification process itself, including the required durability
showing. The Agency, therefore, proposed that the new vehicle emission standards be effective
with the 1994 model year, and that the aftermarket conversions take effect on January 1, 1994.
Additionally, the Agency proposed that manufacturers have the option of complying with these
standards prior to the effective date in order to participate in any applicable emissions averaging,
trading and banking programs, as well as the CAFE program in the case of natural gas-fueled
light-duty vehicles and light-duty trucks.
Summary of the comments: In general, the comments received in response to the issue of lead
time supported EPA's assessment that these standards are not technology-forcing in the sense that
fundamentally new technology must be developed. However, a number of commenters raised
concerns that, although the basic technology required to meet these standards has been
demonstrated at low mileage, the durability of this technology in many cases remains to be
proven. Additionally, one commenter pointed out that there are several mandated requirements
taking effect in the next few years for new vehicles, including Tier 1 and cold CO standards, on-
board diagnostics, and revised evaporative procedures, and that mandating gaseous-fueled vehicle
certification with little lead time may seriously impair the introduction of these vehicles into the
marketplace. Most commenters suggested that, given the need for technology refinement and
durability work, these requirements should not take effect until the 1996 or 1997 model year.
In addition, the heavy-duty engine manufacturers asserted that, under section 202(a)(3)(C) of the
Clean Air Act, EPA is required to provide four years lead time in the case of any new emission
standards. In most cases commenters stated that, regardless of what effective date EPA finalizes,
they support the option of being able to certify prior to the effective date.
EPA response to comments: The Agency agrees that, while current gaseous-fueled vehicle
technology is generally capable of meeting the emission standards contained in today's rule, work
remains in some cases to meet the durability requirements. While the Agency believes that some
current gaseous-fueled engine technologies are capable of demonstrating the required emissions
durability, it does not believe this is the case with some of the newest technologies being
developed Given that each engine family must demonstrate durability during the new vehicle
certification process, the Agency believes that not providing adequate lead time may hinder the
further development of new gaseous-fueled vehicle technology in the short term, which is
contrary to the stated intent of this rule. Thus, today's requirements for new vehicles and engines
8

-------
will take effect with the 1997 model year as requested by some commenters. Manufacturers will
have the option to comply with these provisions prior to the 1997 model year if they choose
The Agency does not believe that this amount of lead time will be a problem from an
environmental standpoint for two reasons. First, the volume of new gaseous-fueled vehicles
produced prior to the 1997 model year is not expected to be that large, given the relatively young
nature of the new gaseous-fueled vehicle market Second, the Agency expects that any new
vehicle or engine family which might be sold in any significant volume prior to the 1997 model
year would be certified and in the process have demonstrated adequate durability. Since there
is much incentive for early compliance in the form of CAFE credits and the emissions banking
and trading program, the Agency would expect the manufacturers of these vehicles to certify
them in order to take advantage of these credits.
Additionally, the Agency does not believe that section 202(a)(3)(C) requires EPA to
provide four years lead time for emissions standards applicable to gaseous-fueled heavy-duty
engines.2 These standards are being promulgated under EPA's general section 202(a)(1)
authority to establish emission standards for any new class of new motor vehicles or new motor
vehicle engines. EPA at no time relied upon section 202(a)(3) for authority to establish these
standards. When operating under the section 202(a)(1) general authority, EPA believes that lead
time considerations are governed by section 202(a)(2), which provides that lead time is to be
allowed as "necessary to permit the development and application of the requisite technology,
giving appropriate consideration to the cost of compliance within such period."
In this context, the four years specified in section 202(a)(3)(C) might serve as a relevant
starting point for determining the appropriate lead time where engine manufacturers must make
changes to their current engine designs in order to comply with new standards for alternative-
fueled engines (as in the case of the gaseous-fueled engine crankcase emission standard). EPA
does not, however, believe that the provisions of section 202(a)(3) constrain EPA's discretion in
establishing emission standards otherwise consistent with section 202(a)(1) and (2). Rather, EPA
believes that the provisions of section 202(a)(3), including the lead time provisions of section
202(a)(3)(C), apply only to standards for gasoline and diesel engines.
Indeed, if section 202(a)(3) were to apply to all standards adopted pursuant to section
202(a)(1), then EPA would be constrained under section 202(a)(3)(A) to adopt standards that
"reflect the greatest degree of emission reduction achievable" through the application of available
technology, rather than standards which correspond to those applicable to gasoline and diesel-
fueled vehicles. EPA does not believe section 202(a)(3)(A) was intended to so constrain EPA
in developing emission standards for alternative-fueled vehicles and engines. And section
202(a)(3)(C) is specifically limited to "[a]ny standard promulgated or revised under this
2 The Agency recognizes it took a somewhat different position in the application of
evaporative emission standards for methanol heavy-duty engines (58 FR 16002, March 24, 1993).
9

-------
paragraph.. the standards for gaseous-fueled engines are not being promulgated under paragraph
(3), but rather "under the general authority of paragraph (1).
This is consistent with EPA's approach in its rule establishing emission standards for
methanol vehicles and standards that correspond with standards already applicable to gasoline and
diesel-fueled vehicles and engines.3 Congress implicitly ratified this prior interpretation in the
1990 Amendments to the Clean Air Act.4 This approach is also consistent with EPA's
conclusion that the Clean Air Act Amendments do not specifically address lead time or phase-in
schedule requirements for heavy-duty onboard refueling control requirements.3
III. Small Volume Procedures for Aftermarket Conversions
Summary of the proposal: It is the Agency's policy that, based on the tampering provisions of
section 203(a)(3) of the Act, aftermarket conversions should not degrade the emissions
performance of the vehicle being converted, and that following a conversion a vehicle should still
meet the emission standards it was originally certified as meeting on any fuels it is capable of
using. Under this policy any conversion which degrades the emissions performance of the
vehicle is considered tampering. In order to clarify how compliance with this policy can be
demonstrated, the Agency proposed that converters can certify as new vehicle manufacturers
using the current new vehicle certification procedures applicable to small volume manufacturers.
The Agency requested comment on whether the volume limit of 10,000 units that currently
defines a small volume manufacturer should apply to conversions as well, or whether, as
proposed, the small volume procedures should apply to all converters, regardless of the
conversion sales volume of the company seeking the certification.
Summary of the comments: In general, the comments received on the aftermarket conversion
provisions were very supportive, with several commenters expressing the need for such
requirements, and none completely opposed. One commenter suggested that these requirements
should only apply to conversions in areas which are not in attainment with national ambient air
quality standards. Comments were received both in favor of and opposed to applying the 10,000
limit to the use of the small volume procedures for conversions. Other comments received
indicated that there was some confusion as to the applicability of the proposed requirements to
conversions done before 1994, as well as to conversions of pre-1994 model year vehicles
performed after December 31, 1993
3	See Notice of Proposed Rulemaking, 51 FR 30983, 30985 (August 29, 1986).
4	See S. Rep. No 101-228, 101st Cong., 1st Sess (Dec 20. 1989) at 101 (referring to
methanol standards).
5	See Notice of Public Hearing and Reopening of Comment Period, 58 FR 30731, 30733
(May 27, 1993).
10

-------
EPA response to comments: The Agency agrees with the comment that the production volume
limits that currently define a small volume manufacturer also apply to converters seeking to
certify as manufacturers under today's program. The Agency expects that the demand for
aftermarket conversions will grow dramatically over the next few years in response to a variety
of state and federal programs. It seems reasonable to require the larger conversion companies
to undergo full new vehicle certification if they choose to get an exemption from the tampering
prohibition by certifying as a manufacturer Thus, the volume limits that currently apply to
manufacturers seeking to certify under the small volume manufacturers provisions will also apply
to converters seeking to certify as manufacturers.
The Agency recognizes that, while the current small volume manufacturers limit as it
applies to new vehicles applies to sales for a particular model year, conversions are routinely
performed on older vehicles. A conversion company may offer conversion systems for vehicles
from several different model years at any given time. Thus, the 10,000 sales volume limit for
obtaining an exemption from the tampering prohibition under the small volume manufacturers
procedures will apply to calendar year sales for the purposes of aftermarket conversions. All
conversions will be included in calculating an aftermarket conversion certifier's total sales for
a given calendar year, including conversions under the requirements of 40 CFR part 88 (clean-
fuel fleets), 40 CFR part 85, and Mobile Source Memorandum No. 1A. Additionally, if the
aftermarket conversion certifier is also a manufacturer of new vehicles, any new vehicles
produced during a given calendar year would be included in the 10,000 limit. Finally, the
Agency recognizes that, even though an aftermarket conversion certifier could certify a system
one year under the small volume manufacturers procedures, during a later year the certifier could
exceed the 10,000 volume sales limit for a conversion or conversions which were previously
certified under the small volume manufacturers procedures. The Agency would expect to revoke
any such certifications under these circumstances.
IV. Refueling Standards
A. Natural Gas
Summary of the proposal: In the NPRM the Agency proposed that, in the case of natural gas
refueling facilities, no refueling hoses which need to be vented down prior to disconnect shall
be vented to the atmosphere. Rather, as is the case with many current natural gas refueling
facilities, EPA expects that such vent-down gases should be routed back to the compressor inlet
rather than being vented to the atmosphere. The timing of this requirement was not explicit in
the NPRM preamble However, the regulatory text stated that the provisions would take effect
with the 1994 model year.
Summary of the comments: In general, the comments received in response to the issue of natural
gas refueling hose venting opposed, to some degree, the proposed prohibition on venting
11

-------
emissions. Some commenters suggested that this requirement is not needed at all given the
extremely small contribution to total methane emissions that vent-down gases represent. Several
commenters pointed out that the upcoming ANSI/AGA NGV1 standard would address EPA's
concerns about refueling emissions from natural gas refueling stations. One commenter pointed
out that this proposed requirement could be interpreted as a zero-emission standard and
questioned the feasibility of such an approach. Some commenters suggested that more lead time
was needed than was proposed. Several commenters pointed out that the cost of controlling these
emissions varied quite a bit depending on the inlet pressure of the compressor. In cases where
the natural gas supply line is at fairly low pressure (i e , 15 psi or less) the gas could be routed
directly into the compressor inlet at low cost. However, in cases where the gas supply pressure
is higher, additional compression equipment would be needed to compress the vent-down gas in
order to route it back into the compressor, raising costs substantially. Also, the cost of such
controls would be much higher for existing installations than for new stations because existing
stations would likely require excavation for the return line plumbing. Finally, some commenters
stated that EPA should not control natural gas refueling emissions since they are primarily
methane, and the Agency only proposed NMHC standards for tailpipe emissions.
EPA response to comments: In the NPRM the Agency mentioned that the natural gas industry
was moving toward the establishment of standard refueling equipment specifications. That effort,
known as the ANSI/AGA NGV1 standard, was recently adopted by the American National
Standards Institute (ANSI) as the standard for natural gas vehicle fueling connection devices
While in its various draft forms, this standard contained a provision limiting the amount of
natural gas that can be vented due to nozzle disconnect. This provision was based on the
proposed onboard refueling vapor recovery (ORVR) standard for gasoline-fueled vehicles of 0.05
grams per gallon of dispensed gasoline.6 As indicated in the draft ANSI standard contained in
the public docket for this rule, the venting provision was deleted from the final ANSI standard
since, at the time of final balloting on the standard, the ORVR rule had not yet been
promulgated. The ORVR final rule was recently promulgated and included a gasoline-fueled
vehicle refueling emission standard of 0.20 grams per gallon of dispensed gasoline.7
The Agency agrees that a zero-emission standard for natural gas vehicles is not reasonable
and believes that, in its draft form, the NGV1 standard addressed EPA's concerns with natural
gas vehicle refueling emissions. Thus, the Agency is using methodology similar to that in the
draft NGV1 standard to apply the 0.20 gram per gallon refueling standard to natural gas vehicles.
Since the mass of natural gas refueling emissions is independent of the fuel tank volume or the
amount of fuel dispensed, a nominal fuel tank capacity must be defined in order to apply the 0.20
gram per gallon refueling standard to natural gas vehicles. In the draft NGV1 standard a nominal
tank capacity of six gasoline gallons equivalent was used for this purpose, and that number is
being used here as well. Using the six gallon equivalent fuel tank capacity in conjunction with
6	52 FR 31162, August 19, 1987.
7	59 FR 16262, April 6, 1994.
12

-------
the 0.20 grams per gallon refueling standard yields a requirement that natural gas refueling
stations will be allowed to vent no more than 1.2 grams of natural gas due to nozzle disconnect.
This requirement will take effect January 1, 1998 for high volume stations, with a two year
extension until January 1, 2000 for small volume stations (those which dispense less than the
energy equivalent of 10,000 gallons of gasoline per month based on the AMFA fuel equivalency
factor)
In addition to the requirements for natural gas refueling stations, EPA is also requiring
natural gas-fueled light-duty vehicles and light-duty trucks be equipped with refueling receptacles
which comply with the recently adopted ANSI/AGA NGV1 standard This requirement will be
unplemented consistent with the timing of the ORVR provisions for other vehicles (three year
phase in beginning with the 1998 model year for light-duty vehicles and the 2001 model year for
light-duty trucks). The Agency expects, however, that all new natural gas-fueled vehicles will
have ANSI/AGA NGV1 nozzles long before this due to the desire for standardized refueling
coupling geometry within the industry.
EPA does not believe that the cost of the refueling station controls is prohibitive and
believes that today's requirement is both feasible and reasonable. Consistent with this view, most
new stations being installed meet this requirement. The Agency agrees that in certain cases, such
as those where additional compression equipment is needed, the cost of retrofitting may not be
reasonable. Thus, for in-use refueling stations which must be reftrofitted to meet this
requirement, the Agency will waive the requirement in situations where the station operator can
demonstrate, to the satisfaction of the Administrator, that compliance with this provision would
require the use of additional compression equipment, or other similar costs. The impact of such
waivers should be minimal given the small number of stations currently operating, and the small
percentage of those stations which would not currently meet these requirements.
The lack of exhaust THC standards in today's rule is a function of cost and legal
constraints, and the Agency believes that control of methane is appropriate where it is feasible
and economically reasonable. Thus, EPA does not believe that the desire to control refueling
emissions from natural gas vehicles is inconsistent with the adoption of exhaust NMHC
standards
B. Liquefied Petroleum Gas
Summary of the proposal: Since LPG is transferred in a sealed system there is little concern
about refueling emissions at the vehicle/pump interface during the actual fuel transfer. Of
concern to the Agency, however, are emissions released when the nozzle is disconnected from
the vehicle At this point any fuel which is trapped in the dead space between the nozzle and
the vehicle receptacle is released In the NPRM the Agency proposed that refueling equipment
be designed so as to prevent this escape of fuel, such as through the use of low-loss, no-bleed
couplings, although no specific numerical standards were included. As with the natural gas
13

-------
provisions in the NPRM, the timing of this requirement was not explicit in the NPRM preamble
However, the regulatory text stated that the provisions would take effect with the 1994 model
year.
Summary of the comments: The Agency received few comments on this particular aspect of the
proposed refueling provisions. The comments that addressed this issue tended to agree with the
need for control. However, the comments otherwise differed. One commenter suggested that
any hardware requirement be performance-based, rather than prescriptive, so as to be consistent
with EPA's previous consideration of refueling controls for gasoline vehicles Also, the lack of
a numerical standard was interpreted as being a zero-emission standard, which one commenter
suggested is infeasible. Another commenter stated that just requiring new refueling nozzles at
all current LPG fueling facilities would cost about $30 million, but provided no supporting
documentation for that claim.
EPA response to comments: The Agency believes that it is appropriate to minimize the amount
of LPG fuel which is vented from the dead space between the refueling nozzle check valve and
the vehicle refueling receptacle check valve but also agrees that a zero-emission standard is
unreasonable. Both the nozzle and the vehicle receptacle geometries play an integral role in the
size of this dead space Thus, any performance specification for vehicle/pump interface refueling
emissions would have to address the nozzle and receptacle as a single system. In the case of
LPG, there is not a standardized geometry for refueling nozzles, at least in terms of the
parameters which would affect this dead space. Thus, it is difficult for the Agency to define a
performance specification such as that which has been considered for gasoline vehicles based
upon an industry standard nozzle geometry. The Agency is aware that the LPG industry is
developing nozzles which dramatically reduce the dead space, especially when used in
conjunction with low-bleed inserts in the vehicle receptacle.
For the reasons just mentioned it seems reasonable to use a two-fold approach to refueling
emissions for LPG vehicles. First, in order to apply the recently promulgated onboard refueling
vapor recovery (ORVR) rule to LPG vehicles, a standard LPG nozzle dead space must be
specified. Once the nozzle dead space is specified, the ORVR standard can be applied to LPG
vehicles when tested with a nozzle meeting this specification. In order to apply the ORVR
standard to LPG vehicles so that both types of vehicles are regulated at the same gram per mile
level the standard must be adjusted to account for the difference in energy density between
gasoline and LPG. Using an equivalency factor of one gallon of LPG being equivalent to 0 732
gallons of gasoline, which was developed for the National Highway Traffic Safety
Administration,8 the ORVR standard of 0.20 gram per dispensed gallon of gasoline is adjusted
to 0.15 gram per dispensed gallon of LPG.
8 "Energy Equivalent Values of Three Alternative Fuels. Liquefied Natural Gas, Liquefied
Petroleum Gas, and Hydrogen", Prepared for the National Highway Traffic Safety Administration
by Abacus Technology Corporation, August 6, 1993

-------
In order to establish a standard for LPG nozzles a nominal fuel tank capacity must be
chosen. Given that most LPG fuel tanks have at least 15 gallons capacity, a standard based on
a fifteen gallon tank volume would suffice for most LPG vehicles. The ORVR test procedure
for gasoline vehicles requires dispensing at least 85 percent of fuel tank volume Since 85
percent of fifteen gallons is 12.75 gallons, a vehicle with a fifteen gallon LPG tank could
typically emit no more than 1.91 grams of fuel vapor during the refueling test (12.75 gallons
multiplied by 0 15 gram per dispensed gallon). Since commercial propane is approximately 0.5
gram per cm3, this would equate to approximately 3.8 cm3 total dead space from which fuel could
be vented upon disconnect of the nozzle for the vehicle to meet the ORVR standard. EPA
allocated about half of this dead volume to the nozzle (and half to the vehicle), thus the standard
allows no more than 2 0 cm3 dead volume in LPG nozzles. This volume is measured from the
nozzle face which seals against the vehicle "O" ring, any dead volume beyond this point would
be attributed to the vehicle. A nozzle which meets this specification can then be used to test the
vehicle using the ORVR procedure and the LPG refueling standard of 0.15 gram per dispensed
gallon of LPG
This approach will ensure that the LPG vehicles will have refueling emissions similar to
those of other vehicles meeting the ORVR standards. A certification testing waiver will be
available for all classes of LPG vehicles to which this standard applies if the manufacturer can
demonstrate, through the use of development or other data, that the vehicle will meet the
standard.
This standard for LPG vehicles will apply to the same classes and model years as the
ORVR rule (i e., three year phase-in beginning with the 1998 model year for light-duty vehicles
and the 2001 model year for light-duty trucks). The requirement for the refueling nozzles will
take effect January 1, 1998 for high volume stations, with a two year extension until January 1,
2000 for small volume stations (those which dispense less than the energy equivalent of 10,000
gallons of gasoline per month). This amount of lead time for refueling stations will allow for
the replacement or retrofit of LPG nozzles during the normal course of replacement or repair of
ui-use nozzles due to wear.
15

-------