Fresh Air: it is recommended that the use of fresh air be maximised where possible for all HVAC purposes. The ratio of fresh air to recirculated air in your building should be increased to 50/50.
Filtration: it is recommended that filtration be used to trap airborne contamination and increase the cleanliness of the air. Please note there are no filters proven to block COVID-19. The use of HEPA filters have been demonstrated to affectively remove a higher percentage of droplets and particles from the air.
Humidity: Scientists believe that the spread of viruses is dramatically reduced when the Relative Humidity (RH) is between 40-60%. RH should be considered when designing an air conditioning system and steps taken to ensure it remains between 40-60% and this may include humidification and dehumidification if required.