This project included laboratory testing and field studies to evaluate the methods and procedures used by both professionals and non-professionals while servicing mobile air conditioning (MAC) systems. A majority of professional technicians used recovery and recharge machines with some using small cans. All non-professional do-it-yourself (DIY) individuals used small cans. Field testing was also conducted to determine refrigerant emissions from nonprofessional servicing. While the data indicated that the majority of the refrigerant was charged into the MAC systems, thirty-three percent was emitted to the atmosphere. Laboratory testing was performed to measure the leak rate from small cans and charging hoses and to compare different leak detection techniques used by professional technicians. In addition, testing was conducted to measure the initial leak flow rate of new MAC systems installed in the 5 most popular vehicles in California.