The focus on COVID-19 transmission shifted in summer 2020 to include the role that ventilation, and heating, ventilating, and air-conditioning systems, might play in preventing the spread of the virus. In October, the Centers for Disease Control and Prevention (CDC) updated its guidance accordingly. The property market response shifted, too. A survey of corporate decision-makers by the Building Owners and Managers Association International in late 2020 found that among five COVID-related health and safety services tenants would pay extra for, “full utilization of 100% fresh air in HVAC systems” topped the list.