SAN DIEGO/May 13, 2003 - Comerica (NYSE: CMA), a leading financial services company, and Clean Air Partners, a leader in the development and commercialization of high-tech solutions to reduce emissions from mobile and stationary engines, announced today that Comerica’s Technology and Life Sciences Division has provided Clean Air Partners with a $4 million credit facility. The majority of the facility - $3 million - is a revolving line of credit; $1 million is an equipment loan.

"We are pleased to provide this credit facility to Clean Air Partners, which has become a leader in the development and supply of emissions reduction solutions," said Chris Woolley, senior vice president and managing director of Comerica’s San Diego-based Pacific Southwest Technology and Life Sciences Division. "We are committed to serving the financial needs of venture-backed companies with compelling technologies, solid business models and management teams, and a desire to work with a technology-focused team that can provide total lifecycle banking."

For more than 10 years, Clean Air Partners has developed low emission vehicle and oil and gas application products, and the company recently expanded into the electric power generation market. Last month, Clean Air Partners announced the closure of its second round of venture capital funding, $8.6 million secured from CIBC Capital Partners, Emerson Electric Co., EnerTech Capital, Exelon Capital Partners, Nth Power and RBC Capital Partners.

"Coming on the heels of our recent equity funding, this credit facility will enhance our ability to support ongoing product and market expansion," said Craig Williams, executive vice president and CFO of Clean Air Products. "In Comerica, we feel we’ve found a bank that understands the unique challenges we face, and has the resources and expertise to be a long-term financial partner."

About Clean Air Partners
Clean Air Partners was founded in 1991 to develop technologies that would allow diesel engines to operate with the low emissions benefits of natural gas while retaining the power, efficiency, longevity, and cost effectiveness of compression ignition engines. Since that time, Clean Air Partners has broadened its scope to include a wider range of diesel and natural gas emissions reduction technologies and applications. Clean Air Partners' time proven products, based on proprietary technologies from 38 active patents, are operating globally: thousands of low emission vehicle and industrial systems utilizing the company’s technology are in service today. Clean Air Partners' sub-components are used in low emission vehicles produced by some of the world's largest automotive and truck manufacturers. For more information about Clean Air Partners and their Dual-Fuel technology, please visit www.cleanairpartners.com.

About Comerica’s Technology and Life Sciences Division
Comerica’s Technology and Life Sciences Division is one of the nation’s leading technology banking practices, offering a wide range of financial services tailored to corporate customers, entrepreneurs and professionals. Veteran bankers provide credit and financial services and products to young, growing, professionally backed technology and life sciences companies, as well as their more mature counterparts. From 18 offices located across the U.S., Comerica’s Technology and Life Sciences Division serves all major technology centers. Comerica is among the 20 largest banking companies in the nation, with nearly $56 billion in assets as of March 31, 2003.

Media Contacts:
Carol A. Tiernan
Clean Air Partners
(858) 332-4805
ctiernan@cleanairpartners.com
or
PJ Jennings
Jennings & Associates (for Clean Air Partners)
(760) 431-7466
pj@free-ink.com
or
Adrienne Moch
Pacifico (for Comerica)
(619) 291-4645
amoch@pacifico.com
or
Keith Turner
Comerica Bank-California
(408) 556-5111
keith_turner@comerica.com