The Environmental Protection Agency (EPA) is looking at possible new criteria for the use of carbon dioxide (CO2) as a vehicle refrigerant, which is a controversial yet logical step in the air-conditioning category.
The EPA has issued a request for comments upon the release of new information on the effects of short-term CO2 exposure on humans. In 2006, the agency proposed to list the use of R-744 (CO2) in vehicle air conditioners as an acceptable alternative to ozone-depleting substances including R-12. However, the agency found that certain use conditions would be necessary due to finding that elevated CO2 levels could cause drowsiness in passengers and drivers.
The EPA-commissioned study, "Review of Health Impacts from Short-Term Carbon Dioxide Inhalation Exposures," found that short-term exposure to CO2 concentrations between 40,000 and 50,000 parts per million (ppm) in confined spaces can cause dizziness and headaches. Hearing and visual impairments have also been noted at exposures as low as 25,000 ppm lasting greater than one hour.
The EPA is considering revising the ceiling limit to 4 percent or 40,000 ppm. This ceiling limit could not be exceeded for any duration inside the passenger compartment.
Some in the air-conditioning service industry have suggested that to convert CO2 into a usable refrigerant would involve adding an odorant to the mix so drivers would be able to quickly detect a leak in the vehicle's cockpit.
The EPA has proposed to require that the motor vehicle air conditioning system be designed to limit automotive exposurer of CO2 concentrations to 3 percent, averaged over a 15-minute span.
Using CO2 in a car would likely decrease fuel efficiency due to the extra load it would place on the engine and the heavier components that would be required. Further, CO2 is highly pressurized and the components involved will have to be thicker to protect driver and vehicle.
Also, climate of the vehicle in question plays a significant role in this refrigerant's success.
For example, "The CO2 would be a better option in cooler climates like Germany," says Elvis Hoffpauir, president of the Mobile Air Conditioning Society. "If you look at places where there's heat, CO2 does not lend itself to those conditions."
The agency is accepting comments on the study and proposed use condition until Nov. 16. For more information, including the report, visit www.regulations.gov.
