Do HVAC systems help with the spread of COVID-19? No one is entirely sure, but it seems very likely. Especially in the case of enclosed indoor spaces. As soon as the COVID-19 pandemic began, fingers pointed to air-conditioning systems as culprits, and scientists now believe a super-spreader event traced back to a restaurant in Guangzhou, in China, which could have started with an asymptomatic person who just happened to cough close to an HVAC fan.
Scientists also believe something similar happened on the Diamond Princess cruise ship, which made headlines over the world, in February 2020. Especially because cruise ships have elaborate inter-connected HVAC systems, which could have aided the coronavirus as it ripped through the cruise population.
HVAC systems Role in COVID-19 spread
And because air-conditioning units typically function indoors, and because the coronavirus (COVID-19 virus) can float about for a little while on respiratory droplets in the air, it should be no surprise at all that HVAC units have come under scrutiny.
In response to this, over the last year, the REHVA (European Federation of Heating and Ventilation Engineers) group actually set out guidelines on what to do, in order to make HVAC units safer. Actually, they went further than that, because on the contrary, properly configured air-conditioning units can actually help to fight the coronavirus, rather than aid its spread.
How AC units can limit viral transmission
By making sure there is a fast and constant exchange of air, AC units can actually wash away virus particles
Despite the apparent doom that HVAC units can kick start super-spreader events, the answer is not to do away with air-conditioning systems. In fact, REHVA recommends the opposite. Instead, what we actually need to do is to reconfigure our AC units so that they can stop coronavirus particles from loitering about in the air, and then settling down.
When virus particles ‘settle’ on a surface, they can be infectious for a time. The technical term for this is a ‘fomite’ and an area that is infectious to touch. By adjusting the settings on AC units to increase the amount of outside air they pull in, and the rate to which this fresh air is distributed indoors, we can make indoor environments much safer. By making sure there is a fast and constant exchange of air, AC units can actually wash away virus particles and prevent fomites from occurring.
What about just opening the windows?
Before modern HVAC units, there was, of course, the humble open window. And sure, open windows is a great way to make sure that air from the inside is quickly and constantly being exchanged with the air from outside. But as we all know, opening the windows is seldom the ideal choice. For example, it isn’t desirable in cold or in air-polluted or noise-polluted spaces. Open windows can even be a hazard if there is a risk of injury or falling.
If you can work in an environment with open windows in a way that’s feasible and manageable, that’s great. They will likely offer similar protection against lingering coronavirus particles. But even if you can, the evidence suggests that a properly configured HVAC system is still safer (not to mention more comfortable, given their ability to regulate temperature) than the age-old open window option.
AC units with high-efficiency particulate air filters
Arguably the most proficient AC units today are those equipped with high-efficiency particulate air (or HEPA) filters. Although, you will struggle to find any outside of surgical theatres and airplanes, where getting the right amount of air exchange is primarily a health and safety issue and not just an issue of comfort.
But as the pandemic has revealed to us, having better optimized HVAC units in public indoor spaces is a health and safety issue. With that being said, could HEPA filters become the norm throughout major public indoor spaces?
HEPA filters
HEPA filters are so reliable because they are made up of thousands of layers that trap all types of particles
HEPA filters are so reliable because they are made up of thousands of layers that trap all types of particles, from dust to viruses. And they operate with an astonishing speed, being able to completely turn over a room’s air up to 30 times per hour. It would almost certainly make sense for HEPA filters to at least be considered for widespread use, but there are some technical issues to work out before their deployment becomes feasible.
Cost aside, these filters can cause ‘dragging’ when attached to traditional AC units, among other issues. But if we are serious about tackling all forms of viruses, including influenza which hospitalizes and kills thousands every year, perhaps the widespread deployment of HEPA filters should be at least thought about in our approach to the ‘new normal’.
Protecting people with proper air conditioning
Whatever the fate of the HEPA filters, we do not have to sit around and wait for a revolution in the HVAC units to keep the general public safe. We can do that right now by equipping and configuring our current systems to properly exchange the rate of air in indoor spaces — to blow away lingering particles and keep surfaces free from fomites.
Fortunately for us, the COVID-19 virus finds it hard to spread outdoors. But that means almost all of the spreading must happen indoors. So, it is crucial that we do all we can from an HVAC perspective to limit the spread of the coronavirus, and indeed all the other infections (including flu), which collectively can infect and hospitalize thousands of people every year.
New infectious diseases emerge, and old ones come and go all the time. With the guidelines that REHVA has put together and some vigilance, our actions could indirectly save many people from falling ill every year. In summary, it’s not rocket science. To make an indoor area safer from the coronavirus, turn your AC unit up. Blow away the germs and stop them from settling down with a frequent exchange of air at all times.