Covid 19 and beyond: a procedure for HVAC systems to address infectious aerosol illness transmission

From pandemic to seasonal, the COVID-19 experience suggests many common respiratory infections rather than likely having a fomite etiology as previously thought, are primarily caused by inhalation of infectious aerosols shed ill persons during coughing and normal breathing talking. Given this new understanding, good news is that, unlike indoor-sourced noxious irritating gases that can only be mitigated practically diluting them with outdoor air ventilation, indoor aerosol illness transmission route addressed circulating already conditioned through commonplace commercial filters. released from breath occupants were an unknown vector disease in healthcare community for decades, understandably HVAC regulations have not issue yet. However, about change. To further end, paper develops formulae needed set recirculation rates such filters design emission rates, HID values, exposure times occupancies, target significantly lower currently airborne infection reproduction rates. The analysis extends equations developed group develop predicting number occur rate spread (reproduction). governing provided exemplified use exposures since (reproduction number) based. Examples using given different settings two case study findings compared their predictions. Some typical office shown relatively low rate. Alternatively, others school classroom or longer flight require increased filtered ventilation flows yield similarly application will interest government industry health standard setting bodies.