They include filtration or germicidal UV: https://www.cdc.gov/coronavirus/2019-ncov/community/ventilation.html https://www.cdc.gov/coronavirus/2019-ncov/communi

They include filtration or germicidal UV: https://www.cdc.gov/coronavirus/2019-ncov/community/ventilation.html https://www.cdc.gov/coronavirus/2019-ncov/community/ventilat... If you do want to bring in outside air, you can use a heat exchange system to minimize the energy impact.