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Holt Architects Coronavirus Computer Cough ModelingComputer model of three coughs in 10 minutes in a common work-space by Holt Archetects

Tompkins County is currently in Phase 4 of reopening, which means more people are returning to work.  A local architecture firm, with offices in Ithaca and Syracuse decided to use a computer model to see exactly how safe the common studio work space in their Ithaca office would be when employees came back to work.  Holt Architects Principal Steve Hugo narrates two videos that show how one infected un-masked person coughing three times over a ten minute period could spread a devastating cloud of droplets over the first 30 feet of their common work-space area, and enough droplets to infect co-workers 50 feet away.  Hugo says the staff wanted to know whether it would be safe to remove their masks while working at their workstations.  The result?  Six feet of separation is not nearly enough for people who are not wearing masks.

"The first model gave us absolute clarity on deciding that all of our staff would be required to wear masks at all times, unless in a single occupancy space with the door closed," Hugo says in the first of two videos.

The first model was not encouraging.  The work stations at Holt's studio take up about 50 feet of the large common work area.  The HVAC heat pump system includes vents near the ceiling.  In the first computer model a worker at one end of the studio coughs three times over a ten minute period.  A huge cloud of droplets at the Human Infectious Dose (HID) level engulfs workstations in the first 30 feet of the studio, and enough droplets to infect other workers make it to the 50 foot mark.  A cloud of droplets that are so dense they are five times the HID level are propelled across the first 30 feet. Hardly any of the droplets make it up to the vents.

The second computer model explores how wearing masks mitigate the spread.  When the coughing employee wears a mask, some droplets do escape, but they are "almost completely contained to the immediate workstation."  But they found that some of the cloud with droplets between 100% and 300% of the HID still traveled between 20 and 60 feet.

"The conclusion here is that if you're indoors for an extended period of time with someone who has contracted the coronavirus, six feet and a mask could be a false sense of security.  The mask is extremely useful in containing a droplet cloud, but it's not 100% effective," Hugo says.

Despite the masks' effectiveness, Hugo says that working indoors in  an enclosed space for an extended period of time with someone who has the coronavirus increases the chances of exposure, even with masks.  he outlined some changes to the physical space that could help reduce the chance of infection, and said the models concluded that the company would be compelled to have a 100% mask mandate in their office.

"Our staff would wear masks at all times in all office public areas," Hugo says. "And would only be able to remove masks in single occupancy rooms."

Holt Architects built a web page on the company site to explain the modeling, and posted additional videos on their YouTube channel.

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