It’s back! R-744

By Jim Taylor, Editor MACS ACtion Magazine

The U.S. EPA has issued a final rule for the use of carbon dioxide (CO2 or R-744)  in motor vehicle air conditioning systems. Wait a minute; didn’t we hear that before? Well, yes, a few years ago, but at the time EPA simply put the gas on the SNAP list and reserved the right to revisit or redefine the rules at their choosing. That’s what just happened.

Instead of simply being “acceptable,” the gas is now termed “acceptable subject to use conditions.” That makes sense, and the prime condition is that the system be specifically designed to use R-744. As you may recall when it was the hot topic a few years ago, a carbon dioxide system operates at much higher pressures than today’s R-134a systems. Thus, to run that gas, every component needs to be beefier, and there can be no retrofits.

Other requirements include unique fittings to prevent connecting the wrong equipment, installation of warning labels, a compressor cut-off switch, and a method of guaranteeing that in case of an evaporator leak the CO2 levels in the cabin do not exceed certain limits.

Interestingly, EPA took great pains to note that they are not advocating any particular method of controlling or detecting CO2 in the cabin. All of that is left to the manufacturer and there are several schools of thought on the matter.

They also said “we do not believe it is necessary to establish any use conditions regarding servicing because the overall environmental and human health risks posed by the use of CO2 in the new systems…is lower than or comparable to the risks posed by other substitutes …” Meaning, since it’s already in the atmosphere as a natural element, you can vent the gas directly without recovering it. It’s already exempt from the recovery requirement for stationary (Sec. 608) equipment, too.

With all the turmoil and delay surrounding the introduction of R-1234yf in North America, it’s interesting to ponder if this recent approval of R-744 for specific systems is just the normal and coincidental grinding of bureaucratic gears (it’s been in the works since 2006) or if some other forces are at work behind the scenes. We do know that all the major OEMs and suppliers were working on CO2 systems a few years ago, and that some had developed their products to a high level before mass-manufacturing costs overcame the effort. Are we in for yet another surprise?

The Mobile Air Conditioning Society’s blog has been honored as the best business to business blog in the Automotive Aftermarket by the Automotive Communications Awards and the Car Care Council Women’s Board!

When having your mobile A/C system professionally serviced, insist on proper repair procedures and quality replacement parts. Insist on recovery and recycling so that refrigerant can be reused and not released into the atmosphere.

If you’re a service professional and not a MACS member yet, you should be, click here for more information.

You can E-mail us at or visit to find a Mobile Air Conditioning Society member repair shop in your area. Visit to find out more about your car’s mobile A/C and engine cooling system.

The 33rd annual Mobile Air Conditioning Society (MACS) Worldwide Training Conference and Trade Show, Be the Best of the Best will take place February 7-9, 2013 at the Caribe Royale, Orlando, FL.


About macsworldwide

Mobile Air Conditioning Society (MACS) Worldwide Founded in 1981, MACS is the leading non-profit trade association for the mobile air conditioning, heating and engine cooling system segment of the automotive aftermarket. Since 1991, MACS has assisted more than 600,000 technicians to comply with the 1990 U.S. EPA Clean Air Act requirements for certification in refrigerant recovery and recycling to protect the environment. The Mobile Air Conditioning Society (MACS) Worldwide’s mission is clear and focused--as the recognized global authority on mobile air conditioning and heat transfer industry issues.
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