Alternative refrigerants Refrigerants with low GWP that come in two broad categories; see “natural refrigerants” and “HFOs” (listed under “synthetic fluorocarbons”).
CO2 equivalent (CO2e) CO2 is the most prevalent greenhouse gas, and its greenhouse gas effects are quite stable over time. Other greenhouse gases are assayed for how much more intense they are than CO2. The EPA’s greenhouse gas equivalencies calculator is a great source for understanding the intensities of the various greenhouse gases.
GWP (global warming potential) a measurement that compares the relative strength of greenhouse gases. CO2 has a GWP of 1, and the GWPs of other gases are measured as multiples of the effect of CO2. CO2 is quite stable, but other greenhouse gases can decay at different rates, so the time period over which the greenhouse gas effect is measured is very important. When a one hundred year time frame is used, this is referred to as the 100 year GWP or GWP100, while a twenty year time frame is used for the 20-year GWP or GWP20.
HVAC/HVACR Heating, Ventilation and Air Conditioning or Heating, Ventilation, Air Conditioning and Refrigeration
Kigali Amendment An Amendment to the Montreal Protocol that governs the global phase down of refrigerants with high global warming potential.
Montreal Protocol The international treaty that governs the global phase out of refrigerants that are Ozone Depleting Substances.
Natural Refrigerant Natural refrigerants stand in contrast to the synthetic fluorocarbons in that their molecules are not created by industrial processes. Examples are carbon dioxide, isobutane, propane, and ammonia. These refrigerants have very low GWPs and can be very efficient with energy use, but special handling is required. For example, carbon dioxide needs a system designed to handle especially high pressure; isobutane and propane are [lightly flammable] [and must be kept away from electrical sparks]; and ammonia is toxic so potential leaks cannot affect inhabited areas.
ODP (Ozone Depletion Potential) This is the standard measure for determining the strength of gases that deplete the ozone.
ODS (Ozone Depleting Substances) * These are the refrigerants that have high ODPs.
SNAP (Significant New Alternatives Policy) —policies written by the EPA to update which refrigerants are acceptable for use in new equipment. Ever since the United States adopted the Montreal Protocol, the EPA has been authorized by the Clean Air Act to determine which “new alternative” refrigerants are safe and effective for use, as well as to regulate at what point older refrigerants are no longer acceptable for production or use. These policies have been implemented over time as the science and technology behind refrigerants has evolved. Originally the new alternatives were aimed at moving us away from Ozone Depleting Substances. Under the Obama administration, Rules 20 and 21 were designed to begin implementing the Kigali Agreement and move us away from high-GWP refrigerants. During the Trump administration, those rules were rolled back, and some of the roll backs were successfully challenged. But when the AIM act was passed, the EPA has regained the authority to pass regulations like those for HFCs.
stratospheric ozone The ozone in the stratosphere that was depleted by CFCs to such an extent that scientists determined we needed to phase out CFCs and reduce their emissions.
synthetic fluorocarbons In the context of refrigerant management, this refers to CFCs, HCFCs, HFCs, and HFOs. These chemicals tend to be patented and stand in contrast to the natural refrigerants.
CFCs (Chlorofluorocarbons) Also known as Class I refrigerants, these were the first synthetic refrigerants, designed in the 1930s. After several decades of use, it became clear that the chlorine atoms in these molecules were responsible for depleting ozone in the stratosphere, which led to them being phased out by the Montreal Protocol in . While CFCs were phased out because they are Ozone Depleting Substances, it is also true that CFCs are very intense greenhouse gases.
HCFCs (Hydrochlorofluorocarbons) Also known as Class II refrigerants, these were the transitional synthetic fluorocarbon replacements for CFCs. They are Ozone Depleting Substances, but their Ozone Depletion Potential is just a small fraction of the ODP for CFCs. HCFCs also have high GWPs, and although they can no longer be manufactured in or imported into this country, legacy equipment that uses HCFCs is still legal, the use of reclaimed HCFCs is still legal, and stockpiles of HCFCs will be around for decades to come. HCFCs also have high GWPs.
HFCs (Hydrofluorocarbons) These are the transitional synthetic fluorocarbon replacements for HCFCs. They have no Ozone Depletion Potential, but they have high Global Warming Potential. The Kigali Amendment to the Montreal Protocol is the international plan to phase down these refrigerants and transition to Alternative Refrigerants, such as HFOs and natural refrigerants.
HFOs (Hydrofluoroolefins) These refrigerants have no Ozone Depletion Potential and very low Global Warming Potential. They also are not flammable. While they have promise as fourth generation refrigerants, researchers have raised questions about the unknown long-term effects of HFOs.
Refrigerant Management — Project Drawdown refers to reducing leak rates of refrigerants and increasing end-of-life refrigerant capture rates as “Refrigerant Management.” But this is also sometimes used as a blanket term that also covers “alternative refrigerants.”