Airflow in passenger cars (re COVID spread) - Printable Version

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Airflow in passenger cars (re COVID spread) - M_T - 01-07-2021

Nothing unexpected, but here's a study on airflow in a typical passenger car with a driver and a passenger in the back right, with a view as to airflows from passenger to driver and from driver to passenger.

Best: all windows open.
Essentially as good: opposite windows open (front right & rear left)
Worst: all windows closed.  But, the air exchanges per hour were higher than recommended for most indoor situations, but it is a tiny space.

A nit I have with this study is that they didn't study partially open windows.  I'd have suggested including 2"-open and half-open, as having wide open windows is quite a blast in the winter.

(A good friend's brother-in-law contracted COVID from his passenger during a 2-hour drive in MN in early December.)

RE: Airflow in passenger cars (re COVID spread) - cardcrimson - 01-11-2021

Working with a couple of companies on localized air purification, including in autos. It's all about the airflow in conditioned spaces, not necessarily the filtration of the HVAC system. So much misinformation out there, and frankly snake oil, it's scary.

RE: Airflow in passenger cars (re COVID spread) - M_T - 01-11-2021

Anything you can tell us?  

One of my work areas is in sealed multi-room facilities.  The HVAC is 5 or 6 decades old (at least in design).  I haven't been in them but once for months.  I am very interested in making sure the air I breathe is COVID-free.

I remember one study where they showed that the localized air purifiers in a hospital apparently blew COVID-laden air to another part of the room where it infected another patient.  The outflow of the purifier was presumably safe, but the Bernoulli effect carried virus-laden air along with the outflow.

Where ever you have airflow, even of clean air, other air gets moved as a result.  Maybe the best way to think of it is not output vents but exhaust vents.

RE: Airflow in passenger cars (re COVID spread) - cardcrimson - 01-12-2021

Can share a lot, but where to begin? Would help to know more about your system and help as I can.

FWIW, I had a conversation a few months back with a systems contractor, who did a study with a major mechanical contractor (fancy term for an HVAC guy) and a major hospital organization. While Covid was found in the HVAC systems, not a single case of transmission through the HVAC had been documented. To your point though, transmission from a shedding person in the conditioned space upstream of a healthy person is problematic. Proper positioning of localized purifiers can greatly reduce the risk, though Computation Fluid Dynamics can greatly help with the analysis, but pretty much has been completely ignored as a tool due to the complexity. . ..

Also, another critical aspect is fast air changes and kill rates. Tracing is set for people unmasked for 15 minutes within six feet--in our products, we're looking at changing and cleaning the air in a conference room completely within half that, and in smaller spaces such as an elevator in less than a minute. Cars, restaurant tables, theatre seats all somewhat similar. The key seems to be, pull in potentially contaminated air quickly, clean it, and send it away from anyone else.

More tomorrow. . . .