This handbook has been developed for technicians servicing room air-conditioners. It was prepared in the course of trainings under the hydrochlorofluorocarbon (HCFC) Phase-Out Management Plans of the Montreal Protocol in India. The handbook provides preliminary and practical information to the technicians that can be applied on day-to-day basis during installation and servicing of air-conditioners. It explains in a simple and easy to understand manner, the principles of air-conditioning. It further provides information on how the refrigerants, if vented into the atmosphere, have an impact on the environment.