MEMORANDUM 

To: Julius Banks and Karen Thundiyil, U.S. EPA 

From: Sarah Menassian, Lauren Smith, Emily Herzog, and Mark Wagner, ICF International 

Date: August 21, 2008 

Re: Air Conditioning Refrigerant Charge Size to Passenger Compartment Volume Ratio Analysis 

(EPA Contract Number EP-W-06-008 Task Order 018, Task 06) 

In this memorandum ICF presents the highest refrigerant charge to compartment volume ratios for each 

class of 2007-2008 model year (MY)1 vehicles. Also included is as a comparison of the ratios for the 

2000 Ford Crown Victoria (the reasonable worst-case scenario vehicle used in the 2005 Risk Analysis for 

Alternative Refrigerant in Motor Vehicle Air Conditioning) and the 2008 Crown Victoria. 

To determine refrigerant charge size to passenger compartment volume ratios, ICF obtained 2007-2008 

model year (MY) refrigerant charge size data2

 from a database maintained by Motor Information Systems

and passenger compartment volume data for 2008 MY vehicles from the Department of Energy’s 

FuelEconomy.gov website and Black Book USA’s database, New Car Cost Guide. The charge to 

compartment volume ratio was calculated for all vehicles for which charge and volume data could be 

obtained.3 Table 1 presents the highest ratios for each vehicle class size and indicates which car has each 

ratio. 

Table 1: Highest Refrigerant Charge to Passenger Compartment Volume Ratios per Vehicle Class 

(MY 2008, unless otherwise indicated) 

CLASS 

Passenger 

Compartment 

Size (m3)

 a

MAC Charge 

Size (grams) 

HFC-134a b

Ratio of HFC134a Charge to 

Compartment 

Volume (g/m3) 

Manufacturer Model 

TWO SEATERS 1.42 907.2 640.75 MERCEDESBENZ 

SL65 AMG (MY 

2007) 

SMALL PICKUP 

TRUCKS 1.48 940 633.27 FORD RANGER 

S.U.V. 3.01 1250 414.96 MERCURY MOUNTAINEER 

(w/ Aux Heat) 

STANDARD 

PICKUP TRUCKS 1.59 632 397.84 TOYOTA 

TOYOTA 

TACOMA 

PRERUNNER REG 

CAB 

 

1

 Data source did not have data for all makes and models in 2008. In particular, data for multiple European cars were unavailable 

due to the fact that European automakers do not release this information until later in the year. For these vehicles, 2007 data were 

used. 

2

 Please note that these data are confidential. 

3

 Both FuelEconomy.gov and the Black Book USA website did not have passenger compartment volume data for all vehicles. 

Generally, volumes for trucks, SUVs, two-seaters, and some vans were not available. These values were estimated using the 

methods outlined in 40 CFR 600, Subpart D (Fuel Economy Regulations for 1977 and Later Model Year Automobiles—

Labeling): sum of ((Head Room * Shoulder Room * Leg Room)/1728) for both front and rear seats (as applicable). 
CLASS 

Passenger 

Compartment 

Size (m3)

 a

MAC Charge 

Size (grams) 

HFC-134a b

Ratio of HFC134a Charge to 

Compartment 

Volume (g/m3) 

Manufacturer Model 

COMPACT CARS 2.63 935.55 355.25 MERCEDESBENZ 

CLS Class (MY 

2007) 

SUBCOMPACT 

CARS 2.29 793.8 346.08 BMW 650i and M6 (MY 2007) 

MINICOMPACT 

CARS 2.10 725 345.99 JAGUAR JAGUAR XKR 

MIDSIZE CARS 2.72 935.55 343.44 MERCEDESBENZ E Class (MY 2007) 

LARGE CARS 2.94 793.8 269.55 BMW 750i (MY 2007) 

SMALL STATION 

WAGONS 2.66 670 251.71 PONTIAC VIBE 

MINIVAN 4.42 1100 248.85 DODGE 

GRAND 

CARAVAN SXT 

WAGON 

VANS 8.20 1600 195.08 CHEVROLET EXPRESS VAN 

(Passenger/Cargo) 

MIDSIZE STATION 

WAGONS c 3.06 475 155.32 KIA RONDO 

a

Source: FuelEconomy.gov, and if not available there, BlackBookUSA.com. 2008 New Car Cost Guide. When volume 

unavailable, value was estimated using BlackBook data and methods at 40 CFR 600, Subpart D. 

b

Source: Motor Information Systems database. These data are confidential. 

c Data were available for only 1 vehicle in this class. By default it has the ‘highest’ ratio. 

Higher ratios signify that in the event of a large leak, drivers and passengers in the indicated vehicle 

would potentially be exposed to higher concentrations of refrigerant than in a vehicle with a lower ratio. 

Calculations show that in a worst case exposure scenario, two-seaters may have the highest concentration 

of refrigerant in the passenger compartment. Of all vehicles analyzed, the 2007 Mercedes SL65 AMG 

two-seater has the greatest refrigerant charge per passenger compartment volume ratio (640.75 g/m3), 

while the 2008 Nissan Rogue SUV has the smallest ratio (139.69 g/m3). In general, the higher ratios 

were seen in the German cars (Mercedes-Benz and BMW) and following those, high ratios were also seen 

in some American S.U.V.s. The accompanying “2008 Analysis_8.19.08.xls” spreadsheet presents all 

ratios calculated, sorted from largest to smallest ratio, overall, and by class. 

In the 2005 Risk Analysis for Alternative Refrigerant in Motor Vehicle Air Conditioning, the Ford Crown 

Victoria was assumed to represent a ‘reasonable worst case scenario.’ Based on the average HFC-134a 

charge sizes (derived from CFC-12 charge sizes) and passenger compartment volumes for each vehicle 

class used in the analysis, large cars have the highest ratio of refrigerant to compartment volume, thereby 

representing a possible worst case scenario. While the 2000 Crown Victoria was a good representation of 

the possible worst case scenario used in the report (being a large car with a ratio close to that of the 

average large car), results of the analysis using 2008 charge size data show that the Mustang currently has 

a higher ratio than the Crown Victoria. In light of this finding, ICF analyzed the 2000 Ford Mustang ratio 
as well when revisiting the assumption that the Crown Victoria represents a worst case scenario. Table 2 

presents the results of this analysis.4

Table 2: Crown Victoria and Mustang Refrigerant Charge to Passenger Compartment Volume 

Ratios (MY 2000 vs. MY 2008) 

2000 2008 

Model Vehicle 

Class 

HFC-134a 

Charge a

(g) 

Passenger 

Compartment 

Volume b (m3)

Ratio -

Charge to 

Volume 

(g/m3) 

HFC-134a 

Charge a

(g) 

Passenger 

Compartment 

Volume b (m3) 

Ratio -

Charge to 

Volume 

(g/m3) 

Crown 

Victoria Large 1,077.28 3.14 342.7 765.44 3.03 252.6 

Mustang Subcompact 963.88 2.32 415.1 737.08 2.41 306.23 

a Source: Ford Motorcraft’s Refrigerant Charge Capacities Reference Sheet. 

b Source: FuelEconomy.gov

As seen in Table 2, even in 2000, the Mustang had a higher ratio than the Crown Victoria. Consistent 

with the findings of the most recent analysis (conducted using 2007/2008 MY vehicles), the higher charge 

to compartment volume ratios are seen in small vehicles. While the most extreme values were seen in 

two-seaters (a finding anticipated by the authors of the 2005 report), relatively high ratios were also seen 

in other small vehicles (particularly minicompacts, subcompacts and compacts). Therefore, the 2005 

report’s decision to not include small cars in the list of possible worst case scenarios may need to be 

revisited. 

Please contact Sarah Menassian at 202-862-1172 or Mark Wagner at 202-862-1155 with any questions or 

comments. 

 

4

 Charge size data for this analysis came from the Ford Motorcraft reference sheet on charge sizes, available at 

http://www.fcsdchemicalsandlubricants.com/supplier/quickref/refrigerant%20charge%20cap.pdf. Compartment volumes were 

taken from FuelEconomy.gov.