Estimating Emissions Associated with 

Portable Fuel Containers (PFCs)
EPA420-R-07-001

February 2007

Assessment and Standards Division

Office of Transportation and Air Quality

U.S. Environmental Protection Agency

Estimating Emissions Associated with 

Portable Fuel Containers (PFCs)

NOTICE

This report does not necessarily represent final EPA decisions or positions. It is 

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.
1.0 INTRODUCTION 

Portable fuel containers (PFCs, or gas cans) are consumer products used to refuel a wide variety 

of gasoline-powered equipment. California has established an emissions control program for gas 

cans which began in 2001. Since then, some other states have adopted the California 

requirements. Last year, California adopted a revised program. 

EPA is planning to propose standards to control VOCs as an ozone precursor and also to 

minimize exposure to VOC-based toxics such as benzene and toluene. Gasoline is highly 

volatile and evaporates easily from containers that are not sealed or closed properly. Although 

an individual gas can is a relatively modest emission source, the cumulative VOC emissions 

from estimated population of 80 million gas cans are quite significant. Left uncontrolled, the 

evaporative emissions from a gas can are up to 60 times the VOC of a new Tier 2 vehicle 

evaporative control system. Gas can emissions are primarily of three types: evaporative 

emissions from unsealed or open containers; permeation emissions from gasoline passing 

through the walls of the plastic containers; and evaporative emissions from gasoline spillage 

during use. 

This report proposes an approach to estimating the VOC inventory associated with PFCs used 

for gasoline. (This analyses does not consider PFCs used for either kerosene or diesel fuel.) 

In 1999, California's Air Resources Board (ARB) proposed a methodology to estimate annual 

emissions from portable fuel containers (PFCs) within California.[1,2] Their approach involved 

first distinguishing and characterizing the various mechanisms (i.e., sources) of emissions of 

hydrocarbons (HCs) and then estimating the frequency of occurrence and emission rates 

associated with each of those sources. 

For most of those sources, the daily emission rates also depend upon these four factors: 

 ● Composition of the PFC (plastic versus metal), 

 ● Whether the PFC was stored open or closed (i.e., a PFC is considered “open” if its vent 

and or spout is uncapped), 

 ● Average size/capacity of the PFC, and 

 ● Frequency the PFC was refilled. 

ARB found (based upon analysis of their survey data) that those four factors were themselves 

dependent upon whether the PFC was used for residential or commercial use. The ARB survey 

results are given in the following table. 

1
 

Table 1

Distribution of PFCs by Usage Type 

Plastic 

Closed 

Plastic 

Open 

Metal 

Closed 

Metal 

Open 

Residential 

Usage 53% 23% 13% 11% 

Commercial 

Usage 33% 39% 18% 10% 

ARB also determined that the average PFC in residential usage had a capacity of 2.34 gallons 

and was refilled 6.4 times annually; the average PFC in commercial usage had a capacity of 3.4 

gallons and was refilled 352 times annually. Combining those survey results leads to the 

estimates that each PFC in a residential unit represents, on average, 14.9 gallons of gasoline 

annually, and each PFC in commercial unit represents 1,206.9 gallons of gasoline annually. 

The analysis also provided ARB with an estimate of the number of PFCs per each residential 

unit (1.8 per household) and per each commercial unit (6.9 per business). Census data (of the 

number of households and the number of businesses within California) were then used by ARB 

to estimate the total number of PFCs within California. 

The Ozone Transport Commission (through its contractor Pechan) modified ARB's methodology 

to apply to Northeastern states.[3] The New Jersey Department of Environmental Protection 

then continued that approach to estimating emissions from PFCs in the state of New Jersey.[4]

2.0 EPA APPROACH 

In this report, EPA proposes to modify ARB's proposed methodology in two ways. The first of 

those modifications was how the number of PFCs (and the number of gallons of associated 

gasoline) was estimated, and the second were revisions to those sources of emissions of HC 

emissions. 

2.1 Estimating Number of PFCs

Rather than assuming that the numbers of PFCs per household and per business were consistent 

across the entire country, EPA used its non-road emissions model (NONROAD2005*) to 

estimate the seasonal (nonroad) consumption of gasoline by source category classification (SCC) 

code for each state plus the District of Columbia. Each SCC code has a unique usage 

(commercial versus residential), a unique ratio of the percent of fuel dispensed from PFCs 

(versus from fuel pumps), and a unique spillage rate (grams per gallon). The spillage (from 

PFCs) in the NONROAD2005 model is assumed to be a constant 17 grams for each refueling 

event. Since the fuel tank capacity varies for different pieces of equipment, the spillage rate (in 

terms of grams per gallon of dispensed gasoline) also varies greatly. (See Appendix A.) Thus, 

 

* The previous draft version of this report (EPA420-D-06-003) was based on 

estimates from the draft NONROAD2004 model. 

2
 

by combining those two outputs of NONROAD2005, EPA was able to estimate (by state) the 

total quantity of gasoline supplied from PFCs as well as the total spillage (from using the PFCs 

to refuel the individual pieces of equipment) for residential usage and for commercial usage. For 

example, running the NONROAD2005 model for calendar year 2005 produced the following 

estimates (obtained by summing the individual state-by-state estimates): 

Table 2

Estimate of Gallons of Gasoline Dispensed Nationwide by PFCs in 2005 

Season 

Residential 

Usage (gallons) 

Commercial 

Usage (gallons) 

Spillage at 

Equipment (tons) 

Winter 2005 107,369,000 303,321,000 10,170 

Spring 2005 281,789,000 553,932,000 17,891 

Summer 2005 456,122,000 742,357,000 24,377 

Autumn 2005 281,374,000 551,282,000 17,824 

Annual 2005 1,126,653,000 2,150,892,000 70,262 

Using ARB’s survey-based estimates of the total annual gallons of gasoline represented by each 

PFC (14.9 gallons for PFCs in residential usage and 1,206.9 gallons for PFCs in commercial 

usage), EPA estimated the number of PFCs in use. This method produced an estimate of 

76,284,000 PFCs in use nationally which is close to industry estimates of 80.5 million PFCs.∗ 

The fact that some PFCs are only used seasonally would increase that calculated number of 

PFCs, bringing it even closer to that industry estimate. This suggests that this approach produces 

estimates that are reasonable on an annual basis. To apply this approach to seasonal estimates, 

we first had to distribute the estimated 6.4 annual refills (for the residential PFCs) on a seasonal 

basis. Distributing those refills proportional to the gasoline used (Table 2) led to an estimated 

average 0.6 refills each winter. Rounding that up to an even 1.0 and distributing the remaining 

refills proportional to the remaining gasoline produced the values in Table 3. The seasonal 

distribution of the refills of PFCs in commercial usage (also given below in Table 3) was 

estimated to be proportional to the distribution of the refills of PFCs in residential usage. 

 

 ∗ The US Consumer Products Safety Commission estimated 80.5 million PFCs in use nationwide, and 

about 20 million additional PFCs are sold annually.[5] Assuming a slow growth rate in the national 

population of PFCs (e.g., the one percent rate estimated from the NONROAD model and illustrated 

in Figure 1), the average useful life of a PFC would have to be between four and five years. That 

estimate of useful life is consistent with the estimates given in that memorandum (i.e., 3-5 years for 

plastic PFCs and 25 years for metal PFCs).

3
 

Table 3

Number of Refills for Each PFC by Season 

 Season Residential Usage Commercial Usage

Winter 1.0000 55.4023 

Spring 1.4755 81.7468 

Summer 2.4000 132.9655 

Autumn 1.4755 81.7468 

Annual 6.3510 351.8614 

This distribution of refills predicts (for calendar year 2005) that approximately 47 million PFCs 

would be in use during the three winter months and approximately 82 million would be in use 

during each of the remaining nine months. EPA proposes to use this seasonal rate of refilling the 

PFCs to estimate the season emissions associated with PFC usage. 

2.2 Revising Sources of HC Emissions

The second modification to ARB's proposed methodology was a revision to those sources of 

emissions of HC emissions, by: 

 – including the emissions produced by displacing the vapor within the PFC and within the 

equipment when each is filled, 

 – including the spillage occurring when the PFC is filled at the pump, and 

 – adjusting the estimates of evaporation/diurnal and permeation emissions to account for 

the fuel RVP and the ambient temperature (using the same approach used by EPA in its 

NONROAD2005 model [6]). 

This modification produced the following list of seven sources: 

 ● Emissions associated with filling the gas can (PFC) at the gas pump 

 (1) Displacement of the vapor within the can 

 (2) Spillage of gasoline while filling the can 

 ● Emissions associated with transporting the gas can to the piece of nonroad equipment 

 (3) Spillage of gasoline during transport 

 ● Emissions associated with using the gas can to refuel the piece of nonroad equipment 

(These emissions are already accounted for in EPA's NONROAD model.) 

 (4) Displacement of the vapor within the nonroad equipment 

 (5) Spillage of gasoline while filling the nonroad equipment 

 ● Emissions (adjusted for changes in ambient temperature) associated with storage of the 

gasoline in the PFCs 

 (6) Emissions due to evaporation (i.e., diurnal emissions) 

 (7) Emissions due to permeation 

Since (as noted above) the spillage and vapor displacement associated with using the PFCs to 

refuel the pieces of nonroad equipment (i.e., items 4 and 5 in the above list) are already included 

4
 

in the estimates of EPA’s NONROAD model; care should, therefore, be taken to avoid double 

counting them in inventory estimates. 

2.2.1 HC Emissions from Vapor Displacement 

Each gallon of gasoline pumped into each PFC or poured into each piece of nonroad equipment 

displaces the same volume of vapor. In EPA’s NONROAD model (for equipment fueled using 

PFCs), the mass of that displaced vapor is a function of the ambient temperature (in degrees 

Fahrenheit) and the Reid Vapor Pressure (RVP) of the fuel, specifically the mass of HC in the 

vapor (in grams) displaced by each gallon of gasoline is given by the following formula: 

exp(-1.2798 + 0.0203*Temperature + 0.1315*RVP) 

Where (ambient) temperature is in degrees Fahrenheit (between 40 and 95° F), and fuel RVP is 

in pounds per square inch (psi). For ambient temperatures under 40° F, the temperature is 

rounded up to 40° F in the formula. Similarly, for ambient temperatures over 95° F, the 

temperature is rounded down to 95° F. 

Since (as noted in Section 2.2) the vapor displaced from the individual non-road equipment is 

already being estimated by EPA’s NONROAD model, care must be taken not to double count 

this quantity in inventory estimates. 

2.2.2 HC Emissions from Spillage at Pump

In EPA’s MOBILE6 model, spillage at the pump is estimated at 0.3128 grams per gallon 

pumped into each on-road vehicle. EPA proposes to use this same estimate of spillage for each 

gallon pumped into each PFC. 

2.2.3 HC Emissions from Spillage During Transport

ARB determined that the spillage of gasoline during transport was dependent upon whether the 

PFC was opened or closed. Specifically, ARB set the transport spillage at 23.0 grams/refill for 

closed PFCs and at 32.5 grams/refill for opened PFCs. EPA proposes to use those same ARB 

estimates in combination with ARB’s survey estimates that, for residential usage, the average 

PFC has a capacity of 2.34 gallons and, for commercial usage, the average PFC has a capacity of 

3.43 gallons. Combining these ARB estimates leads to the following results: 

Table 3

Transport Spillage (grams / gallon) 

Closed PFCs Open PFCs

Residential 

Usage 9.829 13.889 

Commercial 

Usage 6.706 9.475 

5
 

2.2.4 HC Emissions from Spillage During Refueling Non-Road Equipment

As described (in Section 2.1), EPA used its non-road emissions model (NONROAD2005) to 

estimate the spillage (per gallon) for each piece of non-road equipment that is fueled using a 

PFC. Since this spillage for the individual non-road equipment is already being estimated by 

EPA’s NONROAD model, care must be taken not to double count this quantity in inventory 

estimates. If control measures such as automatic fuel shut-offs are used, this could reduce the 

spillage rate to below what is currently assumed in the NONROAD model. 

2.2.5 HC Emissions Due to Permeation

For closed PFCs, ARB estimated the daily permeation rates at 1.6 grams/gallon for plastic 

containers and at 0.06 grams/gallon for metal containers.[2] These estimates were based on 

testing PFCs with an average fill level to be 49 percent. EPA modified ARB’s permeation rate 

for closed metal containers by assuming a rate of zero because fuel does not permeate through 

metal. (For open PFCs, the quantity of evaporative emissions far exceeds the permeation; thus, 

ARB simply used a combined value. See Section 2.2.6.) Based on ARB’s survey results that the 

capacity of the typical PFC in residential use is 2.3 gallons and that the capacity of the typical 

PFC in commercial use is 3.4 gallons, assuming (as ARB did) the average fill level to be 49 

percent, we estimated the average daily permeation for each type of container. Those estimates 

are given in Table 4. 

Table 4

Daily Permeation (grams / container) 

Closed Plastic PFCs Closed Metal* PFCs 

Residential 

Usage 1.80016 0 

Commercial 

Usage 2.63870 0 

* Although ARB estimated permeation from metal cans to be 0.06 

grams per gallon, EPA believes that a permeation rate (through a 

metal container) is more likely to be zero.

Testing has shown that the permeation rate is the same whether the PFC is completely filled with 

liquid gasoline or with saturated vapor. Thus, the total permeation emission is a function of the 

total number of PFCs (in use) rather than of the total amount of gasoline. 

EPA has assumed (in its recent rule makings) that emissions due to permeation are a function of 

ambient temperature, doubling approximately every 10 to 12 degrees Celsius (18 to 22 degrees 

Fahrenheit). We developed an exponential temperature adjustment factor which when applied 

(multiplicatively) to those permeation values allow modeling at various ambient temperatures. 

The formula for that adjustment factor is: 

exp(0.0327 * (Temperature – 85.53)) 

6
 

The temperature adjustment factors were calculated separately for each state and for each day of 

the year and were then averaged to produce estimates for each state for each season of the year 

(see Section 2.3). 

2.2.6 HC Emissions Due to Evaporation/Diurnal

Diurnal (or evaporative) emissions result from fuel expansion and vapor production due to rising 

temperatures during the day. ARB performed 24-hour diurnal testing (with temperatures cycling 

between 65° and 105° F) on PFCs using a fuel with an RVP of 7.0 psi. For closed PFCs, ARB 

estimated the average daily emissions (permeation plus diurnal) for plastic containers at 2.95 

grams/gallon and for metal containers at 0.50 grams/gallon.[2] (As before, the average fill level 

of the containers was 49 percent.) 

Subtracting the estimated daily permeation rates (Section 2.2.5) produced these estimates of 

daily diurnal emissions: 

 ● Closed, plastic PFCs: 1.38 grams per gallon per day 

 ● Closed, metal PFCs: 0.50 grams per gallon per day 

For “open” containers (regardless of material or capacity), a single rate was calculated [2]: 

 ● Open PFCs: 21.8 grams per day (per container) 

Assuming an average daily fill level of 49 percent, we estimated daily diurnal emissions for each 

in-use (closed) PFC to be: 

Table 5

Daily Diurnal Emissions (grams / container) 

Closed Plastic PFCs Closed Metal* PFCs 

Residential 

Usage 1.6 0.6 

Commercial 

Usage 2.3 0.8 

EPA applied an adjustment factor to those values to estimate the diurnal emissions resulting 

from daily temperature cycles different than the 65° to 105° F cycle test used to develop these 

rates as well as from gasoline with different RVPs. These temperature/RVP adjustment factors 

were calculated separately for each state and for each day of the year and were then averaged to 

produce estimates for each state for each season of the year (see Section 2.3). (Estimates of 

future RVPs include the effects of the renewable fuel standards; see Section 3.3.) 

2.3 Determining Ambient Temperatures

As noted in the previous section, the estimates of emissions (except for spillage) are dependent 

upon the temperature of the fuel which is assumed to track the "ambient" temperature. A 

common approach to determining ambient temperatures is simply to use the outdoor 

7
 

temperatures which are readily available. However, some recent testing .[7] suggests that the 

mean temperatures in garages (in which PFCs may be stored) can exceed the (mean) outdoor 

daily temperatures by an average of 10 degrees Fahrenheit.* The differences between outdoor 

and "ambient" temperatures are influenced by factors such as: 

 ● Is a vehicle or a piece of (non-road) equipment with a hot engine stored in that enclosure? 

 ● Where in that enclosure are the PFCs stored (i.e., on a cool floor, on a shelf, near a hot 

engine)? 

 ● How frequently is the door of the enclosure opened (allowing an exchange of air with the 

outdoors)? Similarly, is there a vent (or open window) in the enclosure? 

 ● Is the enclosure shielded either from direct sunlight or from the cooling effects of wind? 

Similarly, is the enclosure insulated? 

Further study would be necessary to precisely quantify the differences between outdoor 

temperatures and the corresponding "typical" PFC storage temperatures. The more the storage 

(or ambient) temperature exceeds the outdoor temperature, the higher will be the estimated 

inventory of VOC emissions from PFCs. EPA believes that half the difference observed in that 

recent study (i.e., 5 degrees Fahrenheit) would be a reasonable estimate of that temperature 

difference. 

Therefore, EPA proposes (for the purpose of estimating PFC inventories) to estimate the daily 

PFC storage temperatures by simply adding 5 degrees Fahrenheit to the average (local) daily 

temperatures. These adjusted temperatures will be used in these analyses. 

3.0 RESULTS 

3.1 Estimates of HC Emissions (Calendar Year 2005) 

Using the NONROAD2005 model for calendar year 2005, we estimated (for each state for each 

season, and for each SCC code) both the total gasoline dispensed by PFC and the total spillage 

occurring when the PFCs were used to fuel the individual pieces of equipment. Summarizing 

those results nationwide (50 states plus the District of Columbia), we obtain the seasonal 

estimates in Table 2 of Section 2.1. 

By the 2005 calendar year, California had already implemented rules which would require the 

PFCs to be designed in such a way as to reduce (probably eliminate) the likelihood of a PFC 

being left in the “open” condition. Additionally, California’s ARB predicts that those changes 

will also reduce both the spillage (occurring when refueling the equipment) by 60 percent as well 

as the permeation rate (for the closed plastic PFCs) by 50 percent. Our estimates for the 2005 

calendar year assume that those rules have been in place long enough for all of the older PFCs to 

be replaced by PFCs that meet the California requirements (see footnote on Page 3). (Note that 

by eliminating the possibility that PFCs can be accidentally left in the “open” condition, not only 

 

 * In a soon to be published report, two researchers from the Department of Environmental Health Sciences at 

the University of Michigan report that a study of at 15 residential garages in Michigan found that the 

temperatures in those garages averaged about five degrees Celsius warmer than outside air. 

8
 

are evaporative plus permeation emissions reduced but also spillage during transport is also 

reduced.) 

Using ARB’s estimates of PFC distribution, we can use the estimates from Section 2.1 to 

estimate PFC usages and then the associated PFC emissions. These estimates of the annual 

inventory of HC emissions resulting from PFCs are summarized in Appendix B-2 on a state by 

state basis. A breakdown of nationwide annual emissions (in tons) for calendar year 2005 is 

given in the Table 6. Fourteen (14) additional states plus the District of Columbia are planning 

to adopt the California PFC requirements. By 2010, we anticipate that all of the PFCs in those 

states will also be compliant with the California rules. We are incorporating that assumption into 

our estimates for calendar years beyond 2005. 

9
 

Table 6

Breakdown of Annual (2005) Nationwide PFC Emissions (tons)

---------------------- PFC Type ---------------------- 

Plastic 

Closed

Plastic 

Open

Metal 

Closed

Metal 

Open Total

Residential Usage:

Permeation + Diurnal 34,311 102,033 7,353 48,798 192,495

Filling PFCs 

 -- Spillage 223 81 46 39 388

 -- Vapor Displacement 2,532 927 532 443 4,434

Transport Spillage 7,011 3,576 1,455 1,710 13,752

Fueling Non-Road 

Equipment*

 -- Spillage 13,560 5,008 2,813 2,395 23,776

 -- Vapor Displacement 2,532 927 532 443 4,434

Commercial Usage:

Permeation + Diurnal 882 3,982 196 1,021 6,080

Filling PFCs: 

 -- Spillage 321 244 115 62 742

 -- Vapor Displacement 3,577 2,799 1,316 718 8,410

Transport Spillage 6,872 7,384 2,462 1,893 18,610

Fueling Non-Road 

Equipment*

 -- Spillage 19,481 15,155 6,979 3,886 45,500

 -- Vapor Displacement 3,577 2,799 1,316 718 8,410

TOTALS 94,877 144,913 25,115 62,127 327,031

TOTALS Excluding Overlap* 54,968 121,025 13,249 54,685 243,926

 * The NONROAD model (and hence local inventories) includes estimates of vapor displacement and 

spillage associated with refueling non-road equipment. However, those NONROAD estimates do 

not exactly match the values in the above table since they do not take into account the California 

control measures. 

From the preceding table, EPA estimates that the nationwide HC inventory resulting from PFCs 

in 2005 to be 327,000 tons per year which is 244,000 tons above what is already being estimated 

by EPA’s NONROAD2005 model. 

10
 

3.1.1 Sensitivity of Estimated VOC Emissions to Ratio of Open PFCs 

These analyses are based on the distribution of PFCs found by ARB in their surveys. As shown 

in Table 1, ARB estimated that 49 percent of the PFCs in commercial use and 34 percent of the 

PFCs in residential use were stored in the open position. As the ratio of open PFCs changes, so 

do the estimated total emissions. In fact, redesigning the PFCs to make it difficult for them to be 

stored in the open position is one strategy used to reduce VOC emissions. For example, as the 

ratio of all PFCs being open varies between 30 and 40 percent, the estimated total VOC 

emissions vary by plus or minus seven percent. 

3.2 Estimates of HC Emissions (Calendar Year 1990) 

Using EPA’s NONROAD model, we repeated the preceding approach and obtained estimates of 

gasoline consumed by non-road equipment (by state for each SCC code) for calendar year 1990 

(instead of for 2005). Assuming the same distribution of PFCs (i.e., open versus closed, plastic 

versus metal), we obtained a national inventory of HC emissions from PFCs as 299,000 tons 

(which is 222,000 tons above what is already being estimated by EPA’s NONROAD2005 model 

for 1990). 

This suggests that the national inventory of HC emissions from PFCs increased by about nine 

percent during the 15 years from 1990 to 2005. That growth rate in HC emissions appears small 

because it is being offset by the effect of California adopting its PFC requirements. As 

illustrated in Figure 1 (in the following section), without the effect of California (and later, 14 

other states plus DC), the annual growth rate would be slightly over one percent. 

3.3 Estimating Annual PFC Emissions into the Future

As noted in Section 3.1, EPA estimated the HC inventory resulting from PFCs for calendar year 

2005 to be 327,000 tons per year. A substantial portion of those emissions are due to the fact 

that many of the PFCs are left open by the users. If the PFCs were redesigned so that neither the 

vent nor the spout could be left "open" while being transported or stored, the resulting 2005 

national inventory would decrease. Additionally, if the PFCs were redesigned to decrease 

spillage by 50 percent, the reduction in HC emissions would be much greater. 

Twelve states plus the District of Columbia (California, Connecticut, Delaware, Maine, 

Maryland, New Hampshire, New Jersey, New York, Ohio, Pennsylvania, Texas, Virginia, and 

Washington DC) already have or will implement controls on the design of PFCs that will reduce 

HC emissions. Additionally, three other states (Massachusetts, Rhode Island, and Vermont) are 

also planning to adopt the California PFC programs which are expected to reduce (for the 

modified containers) spillage (while fueling the equipment) and permeation (each reduced by 50 

percent) and reduce evaporation by designing the PFCs so that they are not easily left open. 

Additionally, California (alone among those 15 states) has adopted more stringent emission 

standards that will require each PFC to emit (permeation plus evaporation) no more than 0.3 

grams of VOC per day for each gallon of capacity. This requirement will be effective July 1, 

11
 

2007. Assuming that gas cans have a typical life of about five years on average, the "new" 

versions of the PFCs should replace virtually all of the earlier versions by 2013. 

Assuming that those 15 states plus DC will have fully implemented their own controls and using 

this methodology, we estimate that that the total annual nationwide HC emissions associated 

with PFCs for 2015 would be 330,000 tons (which includes the "double counted" emissions from 

the NONROAD2005). 

Additionally, the renewable fuel standards (RFS) are expected to affect the RVP of the local 

fuels which in turn would affect the estimates of evaporative emissions and vapor displacement. 

These estimates of future RVP levels are incorporated in the estimates of VOC emissions for 

future years. 

Using this methodology repeatedly, we can obtain estimates of annual PFC emissions for two 

basic scenarios, namely a base case (in which no PFC controls are implemented) and a case in 

which 15 states plus DC implement California type requirements. Those two scenarios are 

plotted in the following graph in which the base scenario is represented by a dotted (black) line 

and the 15-state control scenario (California beginning in 1999) is represented by a solid (blue) 

line. The annual growth in the base scenario (about 1.2 percent annually) is being driven by the 

increasing estimates of PFC related fuel consumption from the NONROAD model.[8]

Figure 1

Comparison of PFC Control Scenarios 

Annual Nationwide VOC Emissions (Tons) from PFCs by Calendar Year

0

100,000

200,000

300,000

400,000

500,000

1990 2000 2010 2020 2030

 Ca le nda r Y e a r 

 Base

 S ta te P rogra ms

12
 

4.0 REFERENCES 

 1. "Proposed Refueling Emission Inventory," by the California Air Resources Board, 

October 1998. 

 2. "Notice of Public Meeting to Consider the Approval of California's Portable GasolineContainer Emissions Inventory" (Mail-Out MSC 99-25). 

 3. "Control Measure Development Support Analysis of Ozone Transport Commission 

Model Rules," prepared for Ozone Transport Commission (OTC) by E.H. Pechan & 

Associates, Inc., March 2001. 

 4. "Estimated VOC Emission Reductions and Economic Impact Analysis for Proposed 

Portable Fuel Containers Rule," by the State of New Jersey Department of Environmental 

Protection, July 2003. 

 5 . "Market Information --- Gasoline Cans," Memorandum from Terrance R. Karels (US 

Consumer Products Safety Commission) to Suzanne Barone, January 3, 2003. 

 6. "Nonroad Evaporative Emission Rates," US EPA Number EPA420-R-05-020 (NR-007c), 

December 2005. (Posted at: http://www.epa.gov/otaq/nonrdmdl.htm#techrept) 

 7. S. Batterman et al., "Concentrations and Emissions of Gasoline and Other Vapors from 

Residential Vehicle Garages," accepted for publication (November 1, 2005) in 

Atmospheric Environment. (Available online at: http://www.sciencedirect.com) 

 8. "Calculation of Age Distributions in the Nonroad Model -- Growth and Scrappage," US 

EPA Number EPA420-R-05-018 (NR-007c), December 2005. (Posted at: 

http://www.epa.gov/otaq/nonrdmdl.htm#techrept) 

13
 

Appendix A–1

Commercial (Non–Road) Equipment Fueled Using PFCs 

By Source Category Classification (SCC) Codes 

Classification SCC Equipment

2 vs 4 

Stroke

% of Fuel 

From 

PFCs

Spillage 

(gr/gal)

Commercial 2260006005 Generator Sets 2 100% 21.250 

 Equipment 2260006010 Pumps 2 98.459% 21.250 

2260006015 Air Compressors 2 100% 15.455 

2265006005 Generator Sets 4 52.297% 7.275 

2265006010 Pumps 4 76.737% 12.798 

2265006015 Air Compressors 4 57.208% 8.437 

2265006025 Welders 4 10.290% 11.333 

2265006030 Pressure Washers 4 77.253% 12.448 

Industrial Equipment 2260003030 Sweepers/Scrubbers 2 100% 26.123 

2260003040 Other General Industrial Eqp 2 100% 16.308 

2265003010 Aerial Lifts 4 1.587% 5.862 

2265003030 Sweepers/Scrubbers 4 18.803% 4.375 

2265003040 Other General Industrial Eqp 4 63.058% 6.741 

2265003050 Other Material Handling Eqp 4 0.156% 11.111 

Lawn and Garden 2260004016 Rotary Tillers < 6 HP 2 100% 56.667 

 Equipment 2260004021 Chain Saws < 6 HP 2 100% 122.324 

2260004026 Trimmers/Edgers/Brush Cutter 2 100% 85.000 

2260004031 Leafblowers/Vacuums 2 100% 24.286 

2260004071 Commercial Turf Equipment 2 100% 6.800 

2265004011 Lawn mowers 4 100% 42.500 

2265004016 Rotary Tillers < 6 HP 4 100% 56.667 

2265004026 Trimmers/Edgers/Brush Cutter 4 100% 85.000 

2265004031 Leafblowers/Vacuums 4 100% 24.286 

2265004036 Snowblowers 4 100% 24.286 

2265004041 Rear Engine Riding Mowers 4 100% 6.954 

2265004046 Front Mowers 4 100% 6.987 

2265004051 Shredders < 6 HP 4 100% 54.839 

2265004056 Lawn & Garden Tractors 4 100% 6.526 

2265004066 Chippers/Stump Grinders 4 100% 1.478 

2265004071 Commercial Turf Equipment 4 100% 3.290 

2265004076 Other Lawn & Garden Eqp. 4 100% 5.141 

Logging Equipment 2260007005 Chain Saws > 6 HP 2 100% 62.408 

Recreational 

 Equipment 

2265001060 Specialty Vehicles/Carts 4 0.021% 4.722 

14
 

Appendix A–2

Residential (Non–Road) Equipment 

By Source Category Classification (SCC) Codes Fueled Using PFCs 

Classification SCC Equipment

2 vs 4 

Stroke

% of Fuel 

From 

PFCs

Spillage 

(gr/gal)

Lawn and Garden 2260004015 Rotary Tillers < 6 HP 2 100% 56.667 

 Equipment 2260004020 Chain Saws < 6 HP 2 100% 201.422 

2260004025 Trimmers/Edgers/Brush Cutter 2 100% 85.000 

2260004030 Leafblowers/Vacuums 2 100% 24.286 

2265004010 Lawn mowers 4 100% 42.500 

2265004015 Rotary Tillers < 6 HP 4 100% 56.667 

2265004025 Trimmers/Edgers/Brush Cutter 4 100% 85.000 

2265004030 Leafblowers/Vacuums 4 100% 24.286 

2265004035 Snowblowers 4 100% 24.286 

2265004040 Rear Engine Riding Mowers 4 100% 6.953 

2265004055 Lawn & Garden Tractors 4 100% 6.526 

2265004075 Other Lawn & Garden Eqp. 4 100% 5.155 

Pleasure Craft 2282005010 Outboard 2 5.001% 5.963 

2282010005 Inboard/Sterndrive 4 0.003% 7.194 

Recreational 2260001010 Motorcycles: Off-Road 2 100% 6.538 

 Equipment 2260001030 ATVs 2 100% 6.538 

2265001010 Motorcycles: Off-Road 4 100% 6.538 

15
 

Appendix B-1

PFC Emissions (Tons / Year) by Source 

(for 1990) 

 Refilling PFC at Pump Spillage Refueling Equipment Permeation 

State

Vapor 

Displacemen

t

Spillage

During 

Transpor

t

Vapor 

Displacement Spillage

Plus 

Evaporation

AL 224.8 15.0 447.1 224.8 1,010.8 4,286.7

AK 24.8 1.9 60.1 24.8 103.2 776.6

AZ 279.1 22.9 647.9 279.1 1,630.1 3,936.1

AR 105.7 8.5 262.7 105.7 533.4 2,813.4

CA 1,532.1 133.9 3,760.8 1,532.1 9,284.9 19,682.1

CO 202.7 18.9 536.5 202.7 1,319.4 2,137.2

CT 123.2 12.0 342.7 123.2 837.2 1,422.5

DE 36.6 3.1 89.1 36.6 217.9 514.9

DC 7.6 0.7 25.0 7.6 56.6 235.1

FL 933.1 72.5 2,055.5 933.1 5,050.7 14,664.5

GA 390.9 32.4 930.8 390.9 2,234.7 5,918.5

HI 58.1 4.0 112.9 58.1 285.3 1,208.2

ID 50.6 4.9 146.3 50.6 316.0 780.1

IL 405.1 36.3 1,058.5 405.1 2,458.1 5,764.9

IN 241.4 19.8 578.2 241.4 1,353.8 3,914.8

IA 99.6 8.3 248.5 99.6 541.9 1,886.4

KS 93.5 8.5 247.9 93.5 567.2 1,457.6

KY 129.1 11.1 340.2 129.1 727.8 2,914.7

LA 168.9 12.1 370.7 168.9 771.4 5,178.9

ME 40.7 4.3 130.7 40.7 297.7 620.4

MD 226.0 21.1 597.8 226.0 1,520.6 2,528.1

MA 199.0 19.1 556.1 199.0 1,322.3 2,561.3

MI 316.9 29.6 886.3 316.9 1,966.1 5,253.7

MN 181.4 15.5 463.1 181.4 992.3 3,281.1

MS 97.0 7.4 230.6 97.0 476.0 2,997.4

MO 212.6 19.0 560.9 212.6 1,271.6 3,427.2

MT 26.4 2.6 81.9 26.4 160.5 506.1

NE 55.0 5.2 154.0 55.0 336.4 911.4

NV 123.4 10.6 295.8 123.4 759.6 1,362.6

NH 44.1 4.5 131.0 44.1 299.6 572.4

NJ 332.9 30.0 857.4 332.9 2,041.2 4,049.9

NM 58.0 5.2 155.6 58.0 358.7 1,050.8

NY 517.1 47.5 1,414.3 517.1 3,095.2 8,473.6

16
 

Appendix B-1 (Continued)

PFC Emissions (Tons / Year) by Source 

(for 1990) 

 Refilling PFC at Pump Spillage Refueling Equipment Permeation 

State

Vapor 

Displacemen

t

Spillage

During 

Transpor

t

Vapor 

Displacement Spillage

Plus 

Evaporation

NC 407.9 31.5 911.8 407.9 2,179.0 6,950.0

ND 17.2 1.8 54.1 17.2 103.9 302.1

OH 507.3 41.1 1,188.5 507.3 2,843.0 7,500.9

OK 139.6 12.1 352.5 139.6 824.4 2,322.6

OR 133.8 12.8 373.6 133.8 864.5 1,889.7

PA 419.5 38.5 1,132.0 419.5 2,644.5 6,498.5

RI 28.3 2.7 80.8 28.3 188.9 422.5

SC 207.8 15.1 438.3 207.8 1,066.9 3,981.0

SD 20.9 2.0 62.1 20.9 124.8 398.1

TN 237.0 18.6 553.4 237.0 1,245.3 4,944.1

TX 875.0 67.6 1,954.5 875.0 4,645.6 15,730.9

UT 70.8 6.7 201.4 70.8 418.4 1,208.1

VT 18.7 1.9 57.6 18.7 127.6 296.3

VA 309.8 27.6 786.6 309.8 1,986.7 3,853.6

WA 225.6 20.5 595.1 225.6 1,399.7 3,174.0

WV 65.4 5.4 170.6 65.4 345.8 1,700.5

WI 166.3 16.4 488.5 166.3 1,089.3 2,512.5

WY 14.8 1.5 48.1 14.8 92.7 265.7

50-

State 11,403.3 972.1 28,226.3 11,403.3 66,389.1 181,040.0

17
 

Appendix B-2

PFC Emissions (Tons / Year) by Source 

(for 2005) 

 Refilling PFC at Pump Spillage Refueling Equipment Permeation 

State

Vapor 

Displacemen

t

Spillage

During 

Transpor

t

Vapor 

Displacement Spillage

Plus 

Evaporation

AL 224.8 17.5 527.1 224.8 1,069.0 5,292.6

AK 29.7 2.2 72.4 29.7 109.1 955.2

AZ 333.8 26.4 751.8 333.8 1,723.4 5,161.0

AR 124.9 10.1 312.6 124.9 564.2 3,471.7

CA 1,637.4 154.9 3,703.0 1,637.4 8,870.9 6,767.7

CO 234.0 21.8 623.4 234.0 1,395.9 2,630.5

CT 129.2 13.8 399.5 129.2 885.9 1,424.3

DE 38.0 3.6 103.7 38.0 230.3 510.7

DC 9.0 0.9 30.4 9.0 59.9 273.6

FL 1,078.4 83.6 2,386.6 1,078.4 5,340.5 18,167.2

GA 452.6 37.6 1,084.7 452.6 2,363.2 7,296.1

HI 67.5 4.6 131.6 67.5 302.9 1,511.5

ID 59.2 5.7 172.6 59.2 334.4 962.5

IL 432.0 42.3 1,239.6 432.0 2,600.8 5,933.4

IN 277.8 23.0 677.6 277.8 1,432.1 4,713.6

IA 116.5 9.7 293.1 116.5 573.4 2,318.4

KS 108.8 9.9 290.8 108.8 600.3 1,792.6

KY 146.2 13.1 404.0 146.2 770.0 3,313.9

LA 199.4 14.2 440.6 199.4 815.9 6,404.7

ME 45.5 5.1 154.8 45.5 315.0 691.7

MD 254.0 24.3 694.1 254.0 1,608.9 2,960.0

MA 209.1 22.2 651.0 209.1 1,399.0 2,576.5

MI 371.2 34.6 1,046.1 371.2 2,079.8 6,476.4

MN 212.2 18.2 546.2 212.2 1,049.9 4,031.7

MS 115.1 8.8 275.4 115.1 503.5 3,706.5

MO 245.4 22.2 659.1 245.4 1,345.2 4,125.5

MT 31.3 3.1 97.7 31.3 169.8 625.4

NE 64.3 6.1 181.5 64.3 355.9 1,120.9

NV 141.5 12.1 341.9 141.5 803.0 1,668.5

NH 47.3 5.2 153.8 47.3 317.0 598.1

NJ 346.5 34.8 998.2 346.5 2,160.2 4,020.0

NM 67.9 6.1 183.5 67.9 379.5 1,295.2

NY 562.4 55.6 1,667.5 562.4 3,275.4 8,968.4

18
 

Appendix B-2 (Continued)

PFC Emissions (Tons / Year) by Source 

(for 2005) 

 Refilling PFC at Pump Spillage Refueling Equipment Permeation 

State

Vapor 

Displacemen

t

Spillage

During 

Transpor

t

Vapor 

Displacement Spillage

Plus 

Evaporation

NC 472.9 36.6 1,064.7 472.9 2,303.8 8,546.9

ND 20.2 2.1 64.4 20.2 109.9 371.4

OH 588.1 47.7 1,388.0 588.1 3,007.6 9,236.1

OK 162.3 14.0 413.0 162.3 871.7 2,860.6

OR 154.8 14.9 437.9 154.8 914.8 2,319.1

PA 472.9 44.9 1,329.5 472.9 2,798.4 7,495.4

RI 30.2 3.2 95.0 30.2 199.9 433.6

SC 241.0 17.6 512.0 241.0 1,128.1 4,898.7

SD 24.7 2.4 73.8 24.7 132.1 489.8

TN 276.8 21.8 651.5 276.8 1,316.9 6,086.9

TX 1,002.5 78.4 2,282.0 1,002.5 4,912.3 18,891.1

UT 82.9 7.9 237.8 82.9 442.7 1,486.5

VT 22.0 2.2 68.3 22.0 135.1 365.5

VA 351.2 31.9 914.9 351.2 2,101.4 4,566.5

WA 246.4 23.8 696.7 246.4 1,481.0 3,493.7

WV 77.6 6.5 203.9 77.6 365.9 2,103.5

WI 186.7 19.1 576.0 186.7 1,152.4 2,836.2

WY 17.6 1.8 57.3 17.6 98.1 327.7

50-

State 12,843.7 1,130.1 32,362.5 12,843.7 69,276.1 198,575.1

19
 

Appendix C-1

Response to Peer Review Comments from Sam Wells 

This report was formally peer reviewed by two peer reviewers (Sam Wells and Sandeep Kishan). 

In this appendix, comments from Sam Wells are reproduced in plain text, and EPA’s responses 

to those comments are interspersed in indented italics. Comments from the other peer reviewer 

appear in the following appendix (Appendix C-2). 

************************************ 

Peer Review of ‘Estimating emissions associated with portable fuel containers (PFCs)’ 

Sam Wells 

January 16, 2006 

Introduction 

Comments are offered on draft documentation of calculation used in ‘Estimating emissions 

associated with portable fuel containers (PFCs). In general, the document is clear and concise, 

making improvements upon previous work done by California Air Resources Board (ARB) and 

others. Further, the proposed methodology is more complete, as it includes all possible modes of 

hydrocarbon emissions from the gas pump to the non-road fuel tank, as opposed to ARB’s single 

focus upon the PFC. 

Similar to other peer review comments I have submitted recently, the introduction appears 

perhaps a little too concise and brief, with the first sentence mentioning an ARB study- without 

an overview of the problem and why estimating PFC emissions are important to understand. 

Also, the types of hydrocarbon emissions are grouped into seven (7) categories, but only six (6) 

are discussed. These are not fatal flaws but a little editing would make the document much more 

readable. 

Two paragraphs have been added to the introduction to explain the importance of 

estimating emissions from PFCs. 

Surveys 

Realizing that the EPA is constrained as to obtaining consumer survey information, one could 

make a case that the ARB survey was (a) a small, (b) old, and (c) perhaps geographically biased 

towards northern and southern California and perhaps not representative the US. These are 

important considerations because the ARB survey findings indicated a very high incidence of 

PFC stored in the “open” condition: 

• Residential open – 34% (random survey = 1,500, response = 26%) 

• Commercial open – 49% (nonrandom survey = 161, response = 94%) 

20
 

These high frequencies have a disproportional impact on hydrocarbon emissions because these 

PFC are freely vented to the atmosphere; thus small changes in the proportions could cause large 

changes to the emissions inventory. 

Therefore, I would recommend a future survey on a national basis to update these statistics and 

the 1991 Outdoor Power Equipment Institute study used to provide NEVES and NONROAD 

spillage and vapor displacement at the gasoline pump. The EPA should consider funding such a 

study if it considers regulation of PFC in the future or analysis of SIP credits; it is understood 

that the current methodology used the “best current science.” 

The reviewer is correct that while this survey is the “best current science,” it is 

very limited. A survey of a larger number of businesses and households over a 

larger geographic area (i.e., more than just one state) might produce somewhat 

different inventory estimates. However, we performed several supplemental 

analyses in which we made relatively large changes to the survey ratios in 

Table 1, and we found that the total estimated VOC inventory changed by less 

than 13 percent. Therefore, EPA does not believe that such an undertaking would 

result in a significantly different estimate of the overall VOC inventory. 

EPA Approach 

Although the ARB survey had its limitations, the EPA application to seasonally and 

geographically allocate PFC is considered to be good. It was also beneficial to have estimates of 

approximately 80 million PFC in the US so as to validate the estimates. A brief analysis of 

residential and commercial landscaping equipment found in NONROAD appears to bolster this 

contention, since those are the leading contributors in terms of PFC (indeed one could almost 

call PFC the “lawnmower and weed whacker gas can inventory”). 

Revising Sources of HC Emissions 

As mentioned previously, this section includes seven hydrocarbon sources but only six are 

mentioned. For document clarity perhaps vapor displacement at the pump should follow the 

exact list as enumerated. Section 2.2.1 seems confusing because it related to both “each gallon 

of gasoline pumped into each PFC or poured into each piece of nonroad equipment...” This 

seems to assume that the displacement of a PFC and the gas tank on an engine are exactly the 

same, which seems awkward at best, and the caveat to not double-count emissions raises even 

more questions. Please clarify this double-counting issue as it is mentioned again in latter text. 

The goal of the analyses in this report was to estimate all of the VOC emissions 

associated with the use of PFCs. When a PFC is filled at the gas pump, vapor 

(containing VOC) is displaced into the atmosphere. Then, when that same PFC is 

used to refuel a piece of equipment, the vapor in the fuel tank of the piece of 

equipment is displaced. Thus, when one gallon of gasoline is pumped into a PFC, 

it displaces 231 cubic inches of vapor from the PFC, and a second 231 cubic 

inches (again) of vapor when it is pour from the PFC into the equipment. Thus, 

there are two vapor displacements occurring. However, EPA’s NONROAD2004 

model already includes that second vapor displacement in its estimates. 

21
 

Therefore, if an estimate of all VOC emissions associated with PFCs is needed, 

then both displacements need to be counted. However, if an inventory of VOC 

emissions is being calculated and if that inventory already includes the estimates 

from the NONROAD2004 model, then that second vapor displacement should not 

be double counted. 

Results 

The ARB rule also adopted in similar form by other states is purported to reduce spillage (from 

gas can to fuel tank) by up to 60 percent. This claim may be exaggerated or have unknown 

effects because by the ARB’s own admission there were some difficulties:1

Shortly after implementing the PFC regulations, consumers began to express complaints 

regarding spillage from the new PFCs. Specifically, ARB staff received complaints 

expressing dissatisfaction with the design and functionality of the PFC’s “spill-proof” 

spouts. ARB staff researched these complaints and learned that while the regulations 

have been successful in reducing emissions from evaporation and permeation, emissions 

from spillage continued to occur. This is a direct result of the spout design. 

Please verify the reductions if possible or state that “good engineering judgment” was used to 

develop these reduction estimates, as the previous SIP reductions appear to be somewhat 

tenuous. 

The reviewer is correct that California’s original approach was not only 

unpopular with the consumers, but it was also not effective in controlling spillage. 

California reduced its estimates of spillage reduction down to zero (i.e., their 

design change had no effect on spillage). However, California has since revised 

its approach to spillage control, and they now believe that the current approach 

will reduce spillage by 60 percent. Since California’s current approach is similar 

to the one that EPA plans to propose in its new (proposed) rule, EPA’s belief 

(based on its own “good engineering judgment”) is that the design will reduce 

spillage by 50 to 60 percent. 

Growth, Useful Life, and Scrappage 

Sections 2.2, 3.1, and 3.3 rely on some rather “shaky” assumptions regarding growth, useful life, 

and scrappage of PFC over time. One of the assumptions is that after four to five years, all the 

plastic PFC will be replaced by new containers, some in areas having the ARB regulations. 

These assumptions are based on NONROAD and an estimate that 20 million PFC (of 80 million) 

are purchased each year. The question as to whether these old, “scrapped” PFC are indeed sent 

to a hazardous or municipal solid waste landfill2 is an interesting one that can lead to some 

conjecture – that perhaps not as many PFC are truly scrapped but are still emitting hydrocarbons 

(diurnal and evaporative). It could be that as families and businesses purchase new equipment, 

 

1 ARB, 2005, ‘Staff report: Initial statement of reasons for proposed 

amendments to the portable fuel container regulations,’ July 29, 2005 

2 Most Subtitle D landfills will not accept hazardous materials including 

gasoline and oil, including any red/orange container (including medical 

wastes) 

22
 

many PFC could simply be added to the inventory. This again would be subject to another 

survey, which was recommended in previous sections, yet may be based in some logic. 

• A cursory review of gas can exchange programs in various states and local regions 

indicated numbers in the thousands, not millions 

• As families acquire more equipment, such as 2-stroke chain saws and personal 

watercraft,1 more gas cans may be needed 

• As landscaping companies2 expand, more PFC are required for additional crew trucks 

In light of such perceived issues, one might recommend a statement saying that there is 

considerable uncertainty as to the PFC scrappage rates, since one would think they would be 

similar to the NONROAD scrappage curves but we simply do not have any hard data. 

The reviewer makes two distinct comments concerning scrappage of PFCs. The 

question as to whether the disposal of PFCs is itself an environmental problem is 

beyond the scope of this study. Those PFCs would be disposed of regardless of 

governmental actions to modify future PFCs. Also, programs dealing with the 

disposal of those PFCs would not be under the control of EPA’s Office of Air. 

As to the estimates of the scrappage rate, EPA agrees with the reviewer that this 

estimated rate is subject to considerable uncertainty. However, if we accept the 

estimate of the PFC manufacturers that there are approximately 80 million PFCs 

in use (in the USA), that this number is slowly rising, and that approximately 20 

million new PFCs are sold each year; then (as stated in the footnote on page 3) 

mathematically we must conclude that the typical PFC has to be replaced every 

three to five years. Therefore, EPA will continue to use this estimate of 

scrappage rate. 

Conclusion 

The PFC document is very well presented; I have made a few minor suggestions. However, it 

may be prudent to consider the level of uncertainty amongst the variables when documenting 

emission inventory tools and resulting inventories. The math itself may be perfect and executed 

with a high degree of precision, but accuracy may suffer as a result of extrapolating large-scale 

inferences from very small surveys. This appears to be the case with PFC. Since documents 

such as this are often used as guidance or models for states, locals, and consultants as boilerplate 

to conduct emission inventories, perhaps a few sentences regarding use of special local surveys 

would be a good idea. 

 

1 Note that personal watercraft are not included in the list of covered 

equipment in Appendix A, but are extensively used in the expanding rental 

market 

2 This may be counter-balanced by an increase in diesel mowers and diesel 

PFC are assumed to have zero hydrocarbon emissions 

23
 

Appendix C-2

Response to Peer Review Comments from Michael Hutcheson 

This report was formally peer reviewed by two peer reviewers (Sam Wells and Michael 

Hutcheson). In this appendix, comments from Michael Hutcheson are reproduced in plain text, 

and EPA’s responses to those comments are interspersed in indented italics. Comments from the 

other peer reviewer appear in the preceding appendix (Appendix C-1). 

************************************ 

Peer Review Comments on the Draft Report 

“Estimating Emissions Associated with Portable Fuel Containers (PFCs)”

This document details comments from the peer review of the draft US EPA report on evaporative 

emissions related to portable fuel container use in the following document: 

“Estimating Emissions Associated with Portable Fuel Containers (PFCs)” 

dated November 18, 2005. 

Comments are provided in general for the overall report and for each subject area including 

population estimates, sources of emissions, ambient temperatures and results. 

General Comments

In general the reviewer found the report confusing in some very important areas. The most 

obvious of which is there is no stated purpose for the report. It appears that the estimates are 

being made because ARB did some similar estimates and now is controlling PFC emissions. If 

this is a guide for states to estimate PFC emissions or alternatively use these emission estimates 

then that purpose should be stated. If these estimates are the basis of federal rule making, then 

that purpose should be included. The description of the CARB methodology should not be the 

introduction but should be included in an analysis of existing data and methodologies. The 

introduction should start with a determination of purpose, history, etc. 

Two paragraphs have been added to the introduction to explain the importance of 

estimating emissions from PFCs. 

The most confusing aspect is the allegiance of the report to its CARB counterpart to the point 

that it the CARB estimates get confused with the EPA estimates. It is abundantly clear in 

Section 2.2 as well as other sections that changes have been made to the CARB methodology. 

Because of these changes, it would be more clear to the reader if sections described EPA’s 

methodology with reference to CARB data when used instead of reference to CARB’s data and 

methodology then EPA’s changes to the methodology and data used. It is recommended that all 

sections which begin with “ARB determined...” be reworded so that the reader is aware that 

“EPA estimates ... based on the information from...”. It appears to the reviewer that the EPA 

24
 

attributes more weight to the CARB method than is due because of the numerous basic 

adjustments EPA has made to the methodology to fit other states. 

The reviewer is correct that EPA’s analysis relies greatly upon ARB’s original, 

groundbreaking analysis. EPA’s goals were slightly different from ARB’s, thus, 

requiring some modifications to ARB’s approach. (ARB seems primarily 

concerned with controlling the VOC emissions from PFCs as a means to control 

ozone during the summer months. EPA similarly plans to use these estimates for 

control of summertime ozone on a nationwide basis. However, EPA is also 

interested in the control of those VOCs on an annual basis as a means of 

controlling certain toxic chemicals contained in the VOCs) In this report, we 

found only one use of the phrase “ARB determined . . .” (Section 2.2.3), and in 

that instance EPA used exactly what ARB had determined (unmodified). 

Population Estimates

The use of the NONROAD model for PFC estimates is an excellent integration of the 

NONROAD model into these estimates. It appears based on the comparison of the EPA estimate 

of 76.284 million units to the industry estimate of 80.5 million units that the methodology is a 

fair estimate. However, the reviewer fails to see how seasonal non-use of containers increases 

the estimate of the number of containers when it is based on the total fuel consumed divided by 

the average fuel consumed per container. Furthermore, it is unclear why EPA revises the 

seasonal estimates of fuel consumed when they are based on seasonal fuel consumption. 

Revising the estimated number of winter refills upward from 0.6 to 1.0 creates a winter bias and 

possibly underestimating emissions. 

The reviewer makes two distinct comments concerning the estimate of the number 

of PFCs First, the estimate of 76.284 million PFCs in use was based on EPA’s 

estimate (from the NONROAD2004 model) of the number of gallons of gasoline 

being dispensed by PFCs However, if some PFCs are out of use for one or more 

seasons, then the total number of PFCs would be the sum of those in use plus the 

number of those not in use. Hence, assuming that some PFCs are used only part 

of the year would increase the total (estimated) number of PFCs. 

As to EPA’s decision to round up the number of refills during winter from 0.6 up 

to 1.0, EPA reasoned that PFCs used for only one season (i.e., winter) would be 

refilled at the beginning of that season, thus insuring at least one refill. PFCs 

used for two or more season would likely require more than a single refill during 

the year; thus, suggesting (but not requiring) a refill during the winter. PFCs not 

used during the winter would not be averaged in to determine the number of 

refills. Thus, EPA believes that assuming (for only those residential PFCs used 

during the winter) that a refill rate of 1.0 was more reasonable than 0.6. Also, 

note that using the 0.6 rate and distributing the remaining 0.4 refills over the 

remaining nine months results in an increase of VOCs during the summer months 

of only four percent. 

It is also unclear to the reader if the seasonal estimates are nationwide or state by state. Because 

the state by state description is lacking, it is assumed the state by state analysis was not 

performed. It seems to the reviewer that a state by state analysis of fuel consumption is 

25
 

appropriate because warmer states would have substantially higher summer consumption and 

lower winter consumption than colder climates. This is because colder climates would have 

additional snow and cold weather nonroad units to maintain. Therefore the reviewer 

recommends that the seasonal fuel consumption estimates be made on a state by state basis. 

EPA used its NONROAD2004 model to estimate fuel consumption related to 

PFCs. These fuel consumption estimates were made for each season and for each 

state. Thus, this component of EPA’s approach already met the reviewers 

suggestion. A statement has been added to the text to the effect that the fuel 

consumption estimates (from Table 2) were calculated by adding the individual 

state-by-state estimates. 

Sources of Emissions

The reviewer recommends that EPA eliminate the discussion of the changes to the CARB 

methodology and limit the discussion to EPA’s methodology and data sources. The description 

of changes to methods only confuses the findings in the report as discussed above. Additional 

discussion of individual sources of emissions are discussed below. 

Vapor Displacement

The reviewer can not tell from the discussion of vapor displacement if EPA conducted separate 

daily analyses for each state based on daily average temperatures or if the estimates made by 

NONROAD for filling equipment are simply assumed equal to the vapor displacement during 

filling of the PFC. Based on the amount of transport spillage, permeation and diurnal emissions 

and equipment refueling spillage, vapor displacement during filling of PFC’s must be greater 

than vapor displacement during fueling of non-road equipment. 

The reviewer is correct that because of gasoline lost to permeation, evaporation, 

and transport spillage the vapor displacement at the time the PFC is filled is 

greater than the vapor displacement when the PFC is then used to fill the 

equipment. However, that spillage estimates matches the estimates from the 

NONROAD2004 model which are already included in the inventory. Also, that 

difference is not only tiny compared to the total VOC emitted, it is not affected by 

EPA’s proposed rules. Therefore, EPA will retain its current spillage estimate. 

Spillage at the Pump

EPA errs by using the Mobile6 model spillage estimates as the basis for estimating spillage on a 

per gallon basis for one basic reason. Simply put, on-road vehicles have much larger tank 

capacities than PFCs. Testing by URS Corporation for Missouri refueling regulations shows that 

spillage during refueling is independent of the amount of gasoline dispensed and is only 

dependent on the number of fills. In other words, spillage is caused at the fuel pump by the act of 

removing the nozzle from the tank regardless of the amount of gasoline dispensed. On average, 

each nozzle will spill approximately 1.5 grams of fuel per refill, even if 1,000 gallons were 

dispensed each time. Based on the average capacity of a container for residential use, EPA 

estimates less than 1 gram of spillage per refill and for commercial containers EPA estimates 

approximately 1 gram of spillage per refill. Therefore on a per gallon of fuel dispensed basis, the 

reviewer believes the Mobile6 model underestimates spillage during refilling of PFC. 

26
 

The reviewer is likely correct that EPA is underestimating the spillage occurring 

when the PFC is filled at the pump. However, since that underestimation is small 

relative to the total VOC emitted and is not affected by EPA’s proposed rule, EPA 

will continue to use the estimates based on its MOBILE model. 

Spillage during Transport

The reviewer believes the EPA methodology for estimating emissions from spillage during PFC 

transport are incorrect and the CARB data underlying these estimates are incorrectly based. 

Transport spillage should be directly proportional to number of gallons as well as distance 

transported. Commercial usage of portable fuel containers is necessary only to transport 

gasoline to a piece of equipment where transport of the equipment to a central refueling location 

is infeasible. Typically, these uses are predominantly related to transport of the container 

between operational locations as in a commercial landscaping business. Because of the large 

number of miles these containers must be transported in comparison to residential PFC usage, it 

is beyond belief that spillage during transport for an open commercial PFC transported 50 miles 

per refill would be less on a per gallon basis than for a residential closed PFC transported less 

than 5 miles from the pump to the residence. For this reason, the reviewer recommends that 

additional consideration of the transport spillage estimates be made. 

The reviewer does not disagree that the estimates EPA proposes to use to 

estimate spillage during transport are “the best available” estimates; rather, he 

only suggests that those estimates might not be “good enough.” EPA agrees with 

the reviewer that those estimates (from Table 3) could be improved. However, we 

do not agree that those estimates are too far from reality to be useful. As we can 

see in Table 6, the current estimate of spillage during transport is actually less 

than six percent of the estimated total VOCs. Therefore, even if we were to 

double the estimated spillage during transport, we would be increasing the total 

inventory of VOCs from PFCs by lest than six percent. Since EPA believes that 

the assumptions underlying Table 3 are directionally correct (i.e., spillage from 

open PFCs is greater than from closed PFCs) and since the sensitivity of the total 

inventory to the assumed spillage rate is small, EPA will retain this approach. 

Spillage during Refueling Non-road Equipment

The reviewer believes the NONROAD estimates of spillage are appropriate for this analysis. 

Permeation

The reviewer agrees the CARB estimates of permeation rates are appropriate to use, however, it 

is not clear in this document if the CARB estimates are on a per gallon of fuel or per gallon of 

capacity basis. It appears that EPA has based their estimates assuming the CARB testing is 

based on a per gallon of gasoline basis, however this is not immediately clear. If additional 

testing has shown the permeation rate is independent of fill level, as stated, then any additional 

testing relied upon should be referenced in this document and any analysis of permeation rate 

included for comparison. 

EPA has used these factors to adjust both permeation and diurnal/evaporative 

emissions to reflect changes both in ambient temperatures and (for evaporation/ 

diurnal emissions) in fuel RVP. Most recently these adjustment factors were used 

27
 

in EPA’s NONROAD2005 model. We added a reference to EPA technical report 

NR-007c which documents these factors. 

EPA does not clearly identify whether the permeation temperature adjustment factor is used for 

these estimates or just previous rule makings. It is presumed that the estimates tabulated in the 

results section include temperature adjustment for permeation. The reviewer agrees with the 

temperature adjustment of permeation, however, it is not clear at what temperature the CARB 

testing data was completed. Since this would influence the adjustment factor, this data should be 

provided in this report. 

As noted in Section 2.2.6, the ARB testing was performed (in a variable 

temperature, diurnal SHED) with ambient temperatures cycling over a 40 degree 

Fahrenheit range (65° to 105° F). 

Evaporation/Diurnal 

EPA does not explain or identify the method used to determine the adjustment factor for diurnal 

emissions. These emissions are closely related to permeation emissions in closed containers as 

illustrated by the CARB data but it is not clear if the same temperature adjustment factor is 

appropriate. EPA needs to identify this adjustment factor for diurnal emissions and explain its 

development. 

As previously noted, EPA used the same temperature adjustment factor that it 

used in its NONROAD2005 model. 

Ambient Temperatures 

The EPA makes a statement regarding temperature testing in PFC storage areas (garages) but 

does not reference this testing. Any testing identified by EPA in this report should be adequately 

referenced. 

Information and reference material regarding that testing program have been 

added. 

The reviewer agrees with the EPA’s method of adjusting ambient temperature for residential 

units but believes that the 10 degree average increase based on testing is more appropriate than 

the 5 degree increase used because it is based on testing. However, for commercial units which 

are assumed to get almost daily refills, it is more appropriate to rely on true daily temperatures 

than to make this correction as storage in a garage can not be presumed. Therefore separate 

adjustments to temperature should be made for residential and commercial PFC emission 

estimate calculations. 

28