Target Air Exchanges Per Hour (ACH)

The goal is to achieve at least 4 to 5 air exchanges per hour (ACH) in order to lower risk of exposure to potentially infectious aerosols. This can be done by enhancing natural ventilation, by increasing the outside air component in heating, ventilation, and air conditioning (HVAC) systems, and by filtration.

In a naturally ventilated space, outside air is circulated through windows and/or doors. Outside air supply can be enhanced using the provided box fans.

In contrast, HVAC equipped rooms provide air exchange driven by a combination of the outdoor air supply plus filtration provided by the system. Portable HEPA air filters can add additional air exchange, when needed.