Engineering Strategies for Airborne Diseases

H V A C S Y S T E M S T R A T E G I E S

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TEMPERATURE AND HUMIDITY

• Small droplets will evaporate fast under any relative humidity (RH), but higher space humidity levels slow the evaporation of large droplets. • Controlled humidity reduces transmission of certain airborne infectious organisms including influenza. • Breathing dry air can cause desiccation of nasal mucosa, which can make occupants more susceptible to respiratory virus infections. • Maintain dry-bulb temperatures per ANSI/ASHRAE Standard 55- 2017. • Maintain RH level between 40% and 60%. This could require humidification during dry & cold and dry & hot days. • Per REHVA (Federation of European Heating, Ventilation and Air Conditioning Associations) Covid-19 guidance document, SARS- CoV-2 has been found highly stable for

2018 Study Humidity decreased Influenza A illness in pre-school

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14 days at 4C (40F)

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1 day at 37C (99F)

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30 minutes at 56C (133F)