The impact of HVAC systems on the spread of the novel coronavirus has been a hot topic since the beginning of the pandemic. However, it is striking that, even given all the discussions and guidance, there is still a lot that we do not know.
Vaguely speaking, we know that crowded spaces with poor ventilation and/or low humidity levels tend to promote virus spread that filtration can help to remove the virus, and that measures such as UV-C radiation can help to disinfect indoor air. But even those suggestions are far from definitive and may be undermined by future study. In general, we ‘think’ that HVAC systems are a factor in spreading the virus, but we are not sure.
Obviously, because the coronavirus is new, much information about the relationship between HVAC and virus spread is based on studies that were carried out in previous years related to other germs, such as SARS-CoV and MERS-CoV, which are similar to SARS-CoV-2, the virus that causes COVID-19. But can this previous testing and studies really be extrapolated to apply to the new disease? The answer is that no one really knows; therefore, such information basically amounts to educated guesses.
There have been some studies since the pandemic began about how HVAC and air flow impact disease spread, some of them in China. However, these studies involve smaller sample sizes and come with caveats, disclaimers, and fine print contained in footnotes about the limitations of the conclusions. Hypotheses are often formulated, but typically the authors have not conducted aerodynamic testing or used other techniques to confirm them.
HVAC and the transmission of pathogens
A rush to provide useful (if flawed) information is understandable in the midst of an emergency
More study is needed, and more time is needed to complete those studies and expand our base of knowledge on this important subject. A rush to provide useful (if flawed) information is understandable in the midst of an emergency. Acting on imperfect information has likely saved thousands of lives. But that success does not diminish the need to pursue more detailed and accurate information.
Those pursuits will likely extend years into the future and well past the aftermath of the pandemic. Studies are needed in specific areas to round out the knowledge base and prepare us to better understand the impact of HVAC on disease spread in the next pandemic. There are no clear answers, and the role of a building’s HVAC systems in transmission of pathogens requires more attention.
Further areas of study
Among other areas, we need studies to cover:
- Epidemiologic factors to measure the role of ventilation, recirculated air, and to adequately quantify ventilation rates
- Use of computer simulations to more accurately track the spread of fine-exhaled droplets.
- More robust examination of the direct role of HVAC in transmitting and removing viable viruses within respiratory droplets or short-range aerosols.
- More research by multi-disciplinary teams that include HVAC engineers, epidemiologists, virologists, infectious disease experts, and other experts working together. Broader studies should cover the fields of epidemiology, engineering and aerodynamics/aerobiology.
- More partnerships between building facilities management departments and those tasked with preventing infection.
Will the pandemic change HVAC?
The pandemic has impacted the HVAC market in many ways. As more of us spend time at home, we become more concerned about issues of air quality and indoor comfort. Some of the changes in our work-life patterns will likely be permanent, which will have a lasting impact on how office buildings are used – and how they are heated and cooled.
It may be that the global pandemic changes the HVAC market for good, both challenging us to expand our technologies and providing opportunities to enhance our businesses. In the future, 2020 may become a pivotal date in the history of the HVAC market – a date after which nothing is ever quite the same. Establishing a sound scientific basis to direct the changing role of HVAC ‘after Covid’ will enable the industry to invest in safer technologies and innovative approaches to drive the future of the industry – and of the world.