Which of these refrigerants has the lowest 100-year GWP in EPA's reference table?
R-290 is far lower than the common HFCs. EPA's reference table lists R-290 (propane) at a 100-year GWP of 3.3, against 1,430 for HFC-134a, 2,088 for R-410A and 3,922 for R-404A.
- R-410A
- R-404A
- R-290Correct answer
- HFC-134a
Why “R-290” is correct
EPA's Technology Transitions GWP Reference Table lists R-290 (propane) at 3.3. The HFCs and HFC blends here are hundreds of times higher, which is why hydrocarbons count as low-GWP refrigerants.
Source: EPA: Technology Transitions GWP Reference Table
Why the other answers are wrong
- R-410A — EPA lists R-410A at 2,088.
- R-404A — EPA lists R-404A at 3,922, the highest of these four.
- HFC-134a — EPA lists HFC-134a at 1,430.
The source, word for word
R-290 (propane) 3.3 IPCC 2007
R-410A 2,088 Calculated
R-404A 3,922 Calculated
The numbers
GWP compares a gas with the same mass of carbon dioxide over 100 years, so a higher number means more warming.
| Refrigerant | Type | 100-year GWP |
|---|---|---|
| HFO-1234yf | HFO | 1 |
| R-290 (propane) | Hydrocarbon | 3.3 |
| HFC-32 | HFC | 675 |
| HFC-134a | HFC | 1,430 |
| R-410A | HFC blend | 2,088 |
| R-404A | HFC blend | 3,922 |
Low GWP does not mean free to vent
Propane is exempt from the venting prohibition only in the end-uses the rule lists, such as household refrigerators and stand-alone retail food units (40 CFR 82.154(a)(1)(viii)). Elsewhere the ban applies, so check the list before assuming.
Keep practicing
- Refrigerant types: CFC, HCFC, HFC and HFO
- What is true of HFO refrigerants
- What may be released without breaking the venting ban
- EPA 608 Core practice test
Unofficial, not affiliated with the EPA or any EPA-approved certifying organization. Questions are original practice written from public EPA material, not real exam questions.