Heating/ventilation/air conditioning/refrigeration (HVACR) technicians (also known as "heating and cooling technicians") are the people who install, maintain, test and repair the machines that control temperature, circulation, moisture and purity of air in residential, commercial and industrial buildings. These systems consist of a variety of mechanical, electrical and electronic components, including motors, compressors, pumps, fans, ducts, pipes, thermostats and switches. Technicians must be able to maintain, diagnose and correct problems throughout the entire system. This article describes the training, personal characteristics, earnings potential, scholarships, job opportunities, certification process, and professional organizations associated with a career in HVACR.