This year’s, 40th international congress on heating, refrigerating and air-conditioning is a rare example of a professional and scientific convention that has been held every year during the four decades, gathering more and more participants and expanding its thematic fields. Since the first conference in 1970 up to this date, our professionals, desirous to improve their skills, expand their knowledge on professional accomplishments and present their ideas and results, meet their colleagues from all the continents. At the same time, the Belgrade HVAC&R congress has received recognition and support from all HVAC&R associations worldwide in its efforts to minimize energy use in buildings, which account for the highest energy use in all the countries worldwide, and focus on renewable sources, which represent a solution for the continued existence of our planet. The congress motto is sustainable development, accepted as a guiding idea, although our future development also depends on what has been done in the past. The accompanying exhibition, which has grown into a unique show of HVAC&R equipment and technology for the past four decades, confirms that anything we learn, analyze and establish is only valuable when applied in practice. Welcome to the 40th jubilee HVAC&R congress and exhibition!