EPA 608

Every Core exam opens with the reasons refrigerant rules exist. This section covers how chlorine and bromine destroy stratospheric ozone, the health and environmental effects of ozone depletion, ozone depletion potential and global warming potential, the Montreal Protocol and the U.S. phaseout schedule, and the Clean Air Act Section 608 rules for certification, venting, refrigerant sales, leak repair, recordkeeping, safe disposal, and enforcement. Expect questions that ask which refrigerants deplete ozone and why, which releases are permitted, who may buy refrigerant, and what happens when the rules are broken.

Ozone (O₃) is a molecule of three oxygen atoms, unlike the two-atom oxygen (O₂) we breathe. Most of the atmosphere's ozone sits in the stratosphere, roughly 10 to 30 miles above the earth's surface. There it absorbs most of the sun's harmful ultraviolet (UV-B and UV-C) radiation. Ozone forms naturally when UV radiation splits O₂ molecules into single oxygen atoms, which then join other O₂ molecules. Ozone near the ground, in the troposphere, is a different matter: it is a pollutant and a component of smog.

CFC and HCFC refrigerants are so chemically stable that they do not break down in the lower atmosphere. Over years they drift up into the stratosphere. There, intense UV radiation breaks the molecule apart and releases a chlorine atom. The chlorine acts as a catalyst: it destroys ozone and then is freed to repeat the reaction, so a single chlorine atom can destroy about 100,000 ozone molecules. Bromine, found in halons and methyl bromide, destroys ozone even more efficiently than chlorine.

Evidence That Refrigerants Reach the Stratosphere

Chlorine from natural sources, such as ocean spray and volcanoes, is mostly water soluble and rains out of the lower atmosphere before it can reach the stratosphere. Chlorine from CFCs does not. Scientists have measured rising levels of chlorine and chlorine monoxide in the stratosphere at the same time and place that ozone levels fall, and the chlorine compounds found there match the breakdown products of CFCs. The most dramatic result is the Antarctic ozone hole, a seasonal thinning that forms each southern spring. Ozone depletion also occurs over the Arctic and at middle latitudes.

The chlorine in a refrigerant molecule is what destroys ozone. Refrigerants with no chlorine or bromine (HFCs, HFOs, hydrocarbons, ammonia, carbon dioxide) have an ozone depletion potential of zero.

When the ozone layer thins, more UV-B radiation reaches the earth's surface. The exam expects you to recognize the major consequences.

Ozone Depletion Potential and Global Warming Potential

Two numbers describe a refrigerant's environmental impact. Ozone depletion potential (ODP) compares a substance's ability to destroy ozone with that of R-11, which is assigned an ODP of 1.0. Global warming potential (GWP) compares the heat a substance traps in the atmosphere over 100 years with that of the same mass of carbon dioxide, which has a GWP of 1. A refrigerant can have zero ODP and still have a high GWP, which is why HFCs, although harmless to ozone, are now being phased down.

Refrigerant	Class	ODP	GWP (100-yr)	TypicalUse
R-11	CFC	10 .	4750 ,	Older low-pressure centrifugal chillers
R-12	CFC	10 .	10900 ,	Older refrigerators and medium-
				temperaturerefrigeration
R-22	HCFC	0055 .	1810 ,	Olderresidentialandcommercialair
				conditioning
R-123	HCFC	002 .	77	Low-pressure centrifugal chillers
R-410A	HFCblend	0	2088 ,	Residentialandlightcommercialair
				conditioning
R-134a	HFC	0	1430 ,	Medium-temperature refrigeration chillers , ,
				vehicles
R-404A	HFCblend	0	3922 ,	Low- and medium-temperature commercial
				refrigeration
R-32	HFC	0	675	Newresidentialairconditioningandheat
				pumps
R-454B	HFC/HFOblend	0	466	Newresidentialandlightcommercialair
				conditioning
R-1234yf	HFO	0	<1	Vehicleairconditioning;blendcomponent
R-744 (CO ₂)	Natural	0	1	Commercialrefrigeration cascadesystems ,

Ozone depletion and climate change are separate problems, but they are linked. CFCs and HCFCs are potent greenhouse gases as well as ozone depleters, so the phaseout protected the climate as well as the ozone layer. Every pound of refrigerant recovered instead of vented helps on both counts.