Campbell-Parnell Campbell-Parnell is a Phoenix-based company that was incorporated as Parnell USA, Inc. in 2002. The company distributes and installs EPA-certified LPG and CNG conversion systems to corporate and government fleets across the United States. The company exclusively uses a bi-fuel configuration for its system, which general manager Tom Campbell says can be used universally on every platform. Campbell says this is one of the most distinguishing characteristics of the company because most fleets are not all made up vehicles that are the exact same. Most fleets, he says, are made up of different model years and different vehicles. Campbell-Parnell's system can be installed the exact same on any vehicle, excepting tank configurations. Their platforms are used for both OEM and afte