Ventilation requirements in hospitals are a substantial contributor to a hospital’s total cost of ownership. Hospitals have high ventilation rates, compared to commercial buildings. These contribute to HVAC capital, maintenance, and energy costs. Ventilation rates are governed by a national standard and by regional codes. Both are largely empirical based, where the logic behind specific requirements is sometimes unclear. The national standard for ventilation rates is ASHRAE Standard 170 - Ventilation for Health Care Facilities. The state of California has, for over 40 years, separately maintained an independent set of ventilation standards. The California standard is contained in Table 4-A of the California Code of Regulations, Title 24, Part 4: California Mechanical Code. Requirements in this table vary from the national standard in several ways. Of particular interest are air flow reductions, allowed in California when 100% outside air is used. This paper considers the comparative impacts to indoor air quality, comfort, infection prevention, cost, and energy. Indoor air quality and comfort are not affected. Infection rates in California are not substantially different than national rates. Systems with 100% outside air can be used to affect cost savings. Use of 100% outside air during economizer hours can also reduce energy consumption. This paper recommends that S170 include reduced air change rates for 100% outdoor air systems, based on the 40 year demonstration of the practice in California, the lack of demonstrable relevant negative consequences to indoor air quality, comfort, or infection prevention, and the benefit of designer flexibility, which can be leveraged toward energy refuction, capital cost reduction, or both.