This is an archived recording of the 2021 online version of the course. The course materials and continuing education credits and/or professional development hours are not available. This course addresses the role of HVAC systems in helping to reduce Hospital Associated Infections (HAI), explaining airborne vs contact transmission. Through filtration, air patterns, air changes, dilution, temperature, humidity, UV, and pressurization the hospital HVAC can either help or hinder efforts to reduce HAI. This course describes the why and how of each of these processes from the perspective of particle physics. The instructor, an experienced healthcare engineering professional, provides unabashed analyses of the controversies regarding the science behind the requirements in ASHRAE Std-170, such as: how many air changes, what level filtration, etc. The course covers production and fate of airborne microorganisms and how people can get infected. HVAC design of airborne infectious isolation rooms, protective isolation rooms, operating rooms, emergency departments, sterile processing departments, and infection control risk assessment are all covered, making the course essential training for anyone designing healthcare facilities.