Even the ever-optimistic and ever-composed Dr Fauci says that expecting a vaccine in 18 months is putting our hopes high. (https://scroll.in/article/961746/dr-faucis-belief-that-well-have-a-covid-19-vaccine-in-18-months-is-optimistic-but-not-improbable) Some European agencies are calling this period (when we have to live in this new-normal, without a vaccine) as the Covid-19 “echo period”. Echo period is a period that is going to last for sometime before the pandemic's last reverberations go down.
Using masks and sanitizer and physical distancing are not the only things that need to be followed carefully. In this article, we briefly discuss an important issue that we need to be aware of during this echo period. This is regarding the air-conditioning systems we use in public and office places.
Action Item: Minimize the use of wall/ceiling mounted split air-conditioner units in public/office buildings.
Issues - When we say split AC here, we mean the systems which have an indoor part and an outdoor part and these parts are connected by electrical wiring and piping for the coolant/refrigerant. Such units do not have a ventilation duct - a duct that would carry outdoor air inside and filter and cool it down before supplying it to the occupied space.
Without any air coming from outside, the split AC unit is just moving the same air in the room, round and round. Secondly, a consequence of installing an AC in a room is that all kinds of entry points for outdoor air in the room (windows, skylights) are blocked off. This is done to prevent cool air from escaping. An unintended consequence is that chances of outside air coming (leaking) in, is furthered reduced. So, having a split AC in a room, you get the cooling but you are quite limited to the stale indoor air with nor fresh outdoor air coming in.
Now, you can clearly see why this is a very bad idea. In spite of all masks and precautions (like sneezing into a tissue) if anyone has Covid-19 (and a very high percentage are asymptomatic) then the viruses will be gradually circulated all through the room, reaching a large number of the people inside (https://wwwnc.cdc.gov/eid/article/26/7/20-0764_article). Since there is no connection with the outside, there is no way for the viral load to get out or for outdoor air to come in and dilute them. Split units do have filters but those are not rated to deal with the small-sized droplets that carry the virus.
For homes, it may barely work because the rooms are small enough that the existing small leakages get enough outdoor air in. For other places, like a classroom or an office or a shop, split units are just not enough for ventilation. They keep circulating stale air, laden with multiple pollutants, increasing your chances of exposure.
The solution: For this summer, if you have such split units, try to go without the use of AC as long as possible. You can try desk or standing fans to help cool you down a little. If you live in a dry area, desert coolers can also help out. If you have to turn on your split unit, then try some of these tricks - better even combine them all!
- Try keeping the internal doors of the building open. This connects up the multiple rooms in a building, creating a larger volume, and diluting any viral load.
- Try keeping the windows open a little. It is bad for the energy bill but again, this is a once in a century event.
- Try having exhaust fans operational in restrooms/toilets. This gives more impulse for outdoor air to leak in, increasing this leakage ventilation rate.
Authors: Asit Kumar Mishra, PhD (BEARS, Singapore) & Amit Kumar Mishra, PhD (University of Cape Town)
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