Over the past several months, a new scientific consensus has been forming around the transmission mechanisms of SARS-CoV-2, the virus that causes COVID-19. Whereas initial reports stated that the primary mechanism was tied to large droplets from close contact interactions, we now know that respirable aerosols also play a large role, with some scientists claiming aerosols are the primary transmission route. There is extensive data surrounding every component of this process.
The aerosol generation process from different activities such as breathing, talking, or talking loudly, along with the data on the efficacy of masks indicate that bars and restaurants, where people have to remove their mask in order to eat and drink, are particularly high risk environments. There is also data showing the stability of virus-laden aerosols in air, and that the aerosols that stay airborne for hours originate from deeper in the lungs where there is a much higher concentration of viral particles. Moreover, the inhalation of viral aerosols enables the viral particles to come into contact with the ACE2 receptors needed to cause infection, whereas a so-called ballistic droplet has a small chance of hitting the eyes, lips, or inner nose.
Overall, the existing practices are worth continuing since many of the preventive measures needed for ballistic particles, such as masks and social distancing, are effective in cutting down aerosol transmission as well. Disinfecting surfaces and handwashing certainly won’t hurt, but with fomite (infected surface/object) transmission playing a minor role in transmission, it is important to be aware that this does not eliminate the threat.
Additionally, plexiglass partitions, while possibly useful in breaking up high density aerosol plumes, are unlikely to do much at even a couple feet in distance when people are not directly facing each other since the aerosols will float around them.
So what do scientists recommend to combat the aerosol threat? It’s simple: more ventilation. There are a number of compelling case studies pointing to regions in restaurants where air was not circulating well, leading to infection. When the weather is nice, dining outside can be rather effective, but this is not possible for every restaurant, nor is it possible throughout the year in most parts of the world.
But increasing ventilation is easier said than done, especially since oftentimes the air being ventilated is being circulated inside a closed system, with a small amount of outdoor air being exchanged. HEPA filters and even MERV-13 filters can eliminate a lot of the aerosols present to ‘locally’ increase effective air exchange without having to pull out tools and start cutting into the HVAC system. Moreover, restaurants frequently have high air exchange rates, but a lot of that air exchange is happening in the kitchens so augmenting this may have limited benefits to those dining, and the distance at which they can safely sit.
HEPA filters can work, but you would need a huge number of them if you want to have all the air in the restaurant filtered every 5-10 minutes. You don’t need to have all the air replaced instantly since risk is tied to dose, where a small amount of exposure is far less likely to lead to infection, and in the cases it does, the lower dose leads to a less severe case.
That’s why Reflow Labs recently built a new type of device, the Airsafe, which is uniquely capable of moving a large amount of air, far faster than a HEPA filter. The Airsafe does away with dense physical filtration and uses optically-enclosed UVC light instead. Being “optically-enclosed” refers to a number of patent-pending techniques for internally reflecting the light to multiply the effective flux hitting the air to levels that scientists have shown result in over 99% inactivation of coronavirus, as well as ensuring that light can’t escape and come into contact with people nearby. The great thing about the Airsafe is it’s based on simple, proven principles that are easy to explain and allow people to dine in confidence. As a bonus, the product name allows you to declare Airsafe Inside.
As winter approaches, the threat of COVID-19 induced economic disaster looms large. The aerosol transmission risk is particularly worrisome since cold, dry air helps aerosols stay in the air longer (which is likely why meatpacking plants have been COVID-19 hotspots). With municipalities going back and forth between open and close regulations throughout the summer, we can expect things are going to get a lot worse for the restaurant industry in the coming months. Although Phase III trials for vaccines are looking promising, those vaccines are not expected to have widespread availability until well into 2021. Even once vaccines are widely available, not everyone will take one, and the infection risk for everyone still remains above zero, especially given the numerous instances of re-infection that have been observed.
Now we have a choice: We can hit ourselves over the head for not thinking of the obvious thing from the get-go, or we can move forward diligently and be happy that a solution exists.
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