Addressing COVID-19 contagion through the HVAC systems by reviewing indoor airborne nature of infectious microbes: Will an innovative air recirculation concept provide a practical solution?

Abstract

As the world continues to grapple with the reality of coronavirus disease, global research communities are racing to develop practical solutions to adjust to the new challenges. One such challenge is the control of indoor air quality in the COVID-19 era and beyond. Since COVID-19 became a global pandemic, the "super spread" of the virus has continued to amaze policymakers despite measures put in place by public health officials to sensitize the general public on the need for social distancing, personal hygiene, etc. In this work, we have reviewed the literature to demonstrate, by investigating the historical and present circumstances, that indoor spread of infectious diseases may be assisted by the conditions of the HVAC systems. While little consideration has been given to the possibility of indoor airborne transmission of the virus, the available reports have demonstrated that the virus, with average aerodynamic diameter up to 80-120 nm, is viable as aerosol in indoor atmosphere for more than 3 h, and its spread may be assisted by the HVAC systems. Having reviewed the vulnerability of the conventional ventilation systems, we recommend innovative air circulation concept supported by the use of UVGI in combination with nanoporous air filter to combat the spread of SARS-CoV-2 and other harmful microbes in enclosed spaces.

Keywords: Aerosols; COVID-19 spread; Coronavirus disease; HVAC systems; Public health; Ventilation systems.

Fig. 1

Schematic representation of potential transmission routes of COVID-19 in an indoor environment.

Fig. 2

Recommended actions against indoor spread of SARS-CoV-12 either as droplets or as aerosols.

Fig. 3

Potential Applications of UVC to Control Microorganisms in Air and on Surfaces. UVC system, in-duct and upper-room level. Source: ASHRAE. Ultraviolet Air and Surface Treatment. ASHRAE Handbook-HVAC Appl 2011. (Edition, 2011).

Fig. 4

Schematic representation of aerodynamic differences between (a) typical mixed-air ventilation system and (b) personalized displacement ventilation system inside the aircraft cabin.

Fig. 5

Inflatable jacket (seat cover) mounted on a typical cabin seat showing air-curtain's air distribution around the passenger.

Fig. 6

Schematic representation of aerodynamic differences between (a) typical mixed-air ventilation system and (b) personalized displacement ventilation system in occupied buildings.