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According to this paper I covered yesterday, saying "stay healthy" ten times releases 1/23rd the volume of liquid droplets as one cough. That suggest saying "stay healthy" 230 times at a consistent pace is equal to one cough. https://chrismasterjohnphd.com/covid-19/how-dangerous-is-the-indoor-air-in-public-spaces
Saying it ten times takes me about 8 seconds. So, saying it 230 times at a consistent pace would take 3.07 minutes. That suggests that speaking for roughly 3 minutes releases the same amount of liquid droplets as coughing once.
The paper also estimated that in a 2x2x2 cubic meter space, it would take a single person 12 minutes to risk inhaling an infectious dose of SARS-CoV-2 previously spread by a single cough.
By extension, it would 12 person-minutes for 3 minutes of talking to risk an infection.
By extension, it would 12 person-minutes for 3 minutes of talking to risk an infection.
I've noticed that many people pull their mask down when talking. Unless you're coughing and sneezing, talking is the main time you need to have the mask covering your face, assuming the mask is filtering the droplet spray.
It would be interesting to estimate how much talking it takes to transact an order at a coffee shop. That might be a good way of estimating how many people should be in the room per unit time per unit space.
Apparently it takes 3 minutes to fulfill a Starbucks order: https://www.chicagotribune.com/news/ct-xpm-2005-04-13-0504130351-story.html#:~:text=At%20Starbucks%2C%20it%20takes%20about,started%20measuring%20five%20years%20ago.
I'm guessing it takes somewhere around 15-30 seconds to place the order. That would suggest that at least one person has to occupy the space for three minutes and let's say 20 seconds of talking need to occur.
The article says it used to take 30 seconds from standing in line to have a Starbucks order fulfilled, so it probably takes less than 30 seconds to order, but the increase in drink complication has made orders more complicated, so I'll stick with 20 seconds.
Let's give 10 seconds between customers and one cash register operating. At maximal capacity, customers would keep ordering so during the 2.5 minute wait after the first person ordered five more would order.
So in 3 minutes spent getting the drink, 6 customers and the cashier barrista have shared one cough worth of time speaking, and, while staggered every 30s, they are basically spending 21 person-minutes in the space, enough to risk more than one infection.
That's assuming a 2x2x2 cubic meter space or 282.5 cubic feet.
Assuming an 8-foot ceiling, this would be 35 square feet. But the average Starbucks is 1500-2000 square feet. https://www.netleaseadvisor.com/tenant/starbucks-coffee/#:~:text=The%20average%20Starbucks%20store%20size,0.50%20%2D%201.00%20acres%20of%20land.
Then again, most coffee shops have closed off all their seating, so have people occupying a much smaller space to order, generally sized on the logic that being six feet apart is sufficient social distancing. You could fix 6 people 6 feet apart with 48 square feet.
That's only a little bit bigger than the space you'd need to confine people in order to ensure that every six people ordering 30 seconds apart risks one infection.
This somewhat overestimates the risk in that it assumes no air ventilation, assumes the space is closed off when in fact the unused seating area will allow air dispersion, and of course assumes that someone has COVID-19 in order to spread the illness.
However, it emphasizes:
1) the need to test the effect of masks specifically on spread microdroplets while talking
2) the need to emphasize people cover their mouth with the mask specifically when talking
3) the need to have more space indoors than required for 6-feet-apart
1) the need to test the effect of masks specifically on spread microdroplets while talking
2) the need to emphasize people cover their mouth with the mask specifically when talking
3) the need to have more space indoors than required for 6-feet-apart
Specifically it would seem wise to leave a margin around infection risk and have 70 square feet for each person spending three minutes in the enclosed space, which is double what you would expect to risk an infection.
The paper I'm referring to is here: https://chrismasterjohnphd.com/covid-19/how-dangerous-is-the-indoor-air-in-public-spaces
You can subscribe to my newsletter here: http://chrismasterjohnphd.com/covid19-updates
I welcome critiques of my math and geometric conceptualization as I'm a bit rusty on math generally speaking. End thread.
