Health care architects and engineers have stressed the need for ventilation since the 1860s. The purpose of this paper is to summarize the many changing concepts behind health care ventilation practices. This paper explains a number of concepts that have evolved and developed over time. It looks specifically at concepts considered relevant to health care spaces. It compares those developments to the history of ventilation rates used in other nonresidential buildings. Topics covered include: Progression from miasma to germ theory and the architectural influence of miasma, the origin of 2 ach as an outside air ventilation standard, discovery of airborne germs, historical progression of nonresidential outdoor air rates and comparative progression of health care outdoor air rates, the advent and progression of health care codes in the U.S., use of filtered or outdoor air as a sepsis control technique, ventilation reforms and pressures resulting from the U.S. energy crisis of the 1970s, tuberculosis and construction dust controls, historical progression of clean air technology and relevance to health care spaces, modern advancements in nonresidential ventilation, and the consensus of literature on the relevance of air quality to infection control.