Request to Use an Alternate GWP for

Hexafluoropropylene (CAS Number: 116-15-4)

Summary:

EPA recently promulgated a mandatory reporting regulation for Fluorinated Greenhouse 

Gases (F-GHG). The regulation requires facilities to monitor and report CO2-equivalent 

F-GHG process vent emissions, if those emissions exceed a threshold of 10,000 metric 

tons CO2-equivalent per year. [1] Estimated CO2-equivalent emissions are obtained by 

multiplying the F-GHG mass emissions by the Global Warming Potential for the 

individual fluorinated gases that comprise the flow. EPA has provided a table of 100-

year time horizon GWP values for about 70 individual F-GHG, and specifies that these

values are to be used for the purpose of computing CO2-equivalent emissions. [2] A 

default GWP value of 2,000 is to be used for any F-GHG not listed in Table A-1. The 

regulation allows a facility to request a lower provisional GWP when clear scientific 

evidence exists to support such a lower value.

Table A–1 does not list a GWP for hexafluoropropylene. Hexafluoropropylene is a shortlived fluorinated alkene. The default GWP value of 2,000 is inappropriate for such gases 

and a substantial body of evidence in the peer-reviewed scientific literature has 

established that the GWPs of fluorinated alkenes are modest. Kinetic rate constants for 

the atmospheric degradation of hexafluoropropylene have been measured in an 

environmental chamber; the atmospheric lifetime of hexafluoropropylene has been 

estimated as 6 days; the infrared spectrum of hexafluoropropylene has been accurately 

measured and the GWP of hexafluoropropylene has been estimated as 0.25 relative to 

CO2 with a 100-year integration time horizon. DuPont is requesting a provisional 

GWP of 0.25 be assigned for hexafluoropropylene.

Evidence Supporting Request:

F-GHG Identity: Hexafluoropropylene

Chemical Formula: C3F6

CAS Number: 116-15-4

Estimated GWP: 0.25 relative to CO2 with a 100-year integration time horizon 

Data and analysis: Acerboni et al. have measured kinetic rate constants for the vapor 

phase reaction of hexafluoropropylene with OH, NO3 and O3. [3] A chemical transport 

model was applied to calculate the atmospheric distributions and lifetime of 

hexafluoropropylene; the global and yearly averaged lifetime was calculated as 6 days. 

Quantitative infrared cross-sections of hexafluoropropylene were obtained at 298 K in the 

region 100-2600 cm-1, and radiative forcing calculations were performed assuming either 

constant vertical concentration profiles or the distribution derived from the chemistry 

transport model. A GWP of 0.25 relative to CO2 with a 100-year integration time horizon

was established. 
The methods used in determining this GWP value are essentially identical to those used 

for the values obtained for the gases listed in Table A-1: (1) the kinetic rate constants for 

reaction with critical atmospheric oxidants were measured and an atmospheric lifetime 

was determined; (2) the infrared absorption spectrum of the substance was measured; and 

(3) the atmospheric lifetime and infrared absorption spectrum were incorporated into a 

radiative transfer model to estimate the contribution of the substance to greenhouse 

forcing. 

Based on this publication in the peer-reviewed literature, DuPont requests that a 

provisional GWP of 0.25 be assigned for hexafluoropropylene.

1. "Mandatory Reporting of Greenhouse Gases: Additional Sources of Fluorinated 

GHGs; Final Rule", Federal Register 75:230 (December 1, 2010) p.74774.

2. "Table A-1 to Subpart A of Part 98—Global Warming Potentials": Table A-1 in 

40 CFR part 98, subpart A.

3. Acerboni, G., et al., Atmospheric degradation and global warming potentials of 

three perfluoroalkenes. Atmospheric Environment, 2001. 35(24): p. 4113-4123.