An overview of solutions for airborne viral transmission reduction related to HVAC systems including liquid desiccant air-scrubbing

Abstract

The world is facing on-going challenges due to the spread of the coronavirus SARS-CoV-2, which is affecting the health of people worldwide and the economy of countries. Social distancing, lockdown and quarantine measures have been implemented globally to limit the spread of the virus with a profound impact on people’s lives. These are interventions which are not considered to be permanent and reproducible in the long-term. As more evidence is growing around the airborne transmission routes of the virus, as previously identified for other viruses such as tuberculosis, measles, influenza and coronaviruses, the role of heating, ventilation and air-conditioning (HVAC) systems in buildings, enclosed spaces and public transport in limiting the transmission of airborne pathogens has become a topic of significant relevance. Although the HVAC strategies recommended by professional engineering associations are capable of minimising the transmission of airborne pathogens, they are also responsible for an increase in energy consumption and possibly in a reduction of thermal comfort for occupants. The objective of the study is to review the role of HVAC in airborne viral transmission, to estimate the energy penalty associated with the implementation of the main HVAC strategies for transmission reduction and understand the potential of liquid desiccant technology as an air scrubber. That is capable to a) energy-efficiently control temperature and humidity in buildings, enclosed spaces and public transport; b) increase the indoor air quality by offering the conditions of temperature and humidity less favourable to the growth, proliferation and infectivity of microorganisms; and c) inactivate pathogens. The main factors involved in the process of the inactivation of viruses or pathogens by liquid desiccant solutions are also described together with possible modifications to the solutions to increase their heat and mass transfer and sanitising characteristics. The study is ended by an economic evaluation of the potential energy benefits resulting from the use of liquid desiccant technology. It is concluded that the technology could be particularly favourable in those buildings where humidity control and/or moisture removal is required or in buildings where viruses are more likely to be present, such as in healthcare facilities/operating rooms, or in the event of an airborne viral outbreak.