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COVID questions: HVAC spread; indoor swimming; national debt

August 13, 2020 By Kristina LeVan

Editor’s note: We will be publishing answers to questions about COVID-19 and the pandemic each week in this COVID questions column. If you have a question, please email it to

Q: What about transmission of virus particles throughout a building via the HVAC system? Unless there are HEPA filters installed in campus buildings, couldn’t the virus be circulated from room to room via the air circulation system?  Couldn’t this allow a superspreader event to occur if there is an infected person in the building, even if the people in my classroom are not infected?

A: To-date, there have not been any confirmed cases of COVID-19 where a positive person is shedding the virus via “long-range” aerosol transmission through a building’s HVAC system.  The confirmed cases have been by infection of a positive person to other individual(s) occupying the same space.

Douglas Reindl, professor, engineering professional development, mechanical engineering; director, Industrial Refrigeration Consortium

Q: If workers come into a home and are infected but don’t know it yet, will them being masked and the home being air-conditioned help? I’m not sure how much ventilation is necessary?

A: A few things to think about if this is a concern for you.  First, consider whether or not the in-home work necessary.  If the work is not urgent, you could consider postponing until a future date.   Second, you might contact the company who is providing the workers and ask what means and measures they are using to ensure their workers are not COVID-positive.  This could include simple things like daily temperature checks and periodic testing of their field personnel.  Infection risk will be reduced if the time they are in your home is minimized.  Wearing a mask provides some protection if properly fit and worn while indoors.  If working is commencing in a specific area, such as your basement, you could avoid that area for a day or two after their work concludes.  If weather conditions are favorable, the work area can be ventilated by opening windows.

Douglas Reindl, professor, engineering professional development, mechanical engineering; director, Industrial Refrigeration Consortium

Q: The US has taken on trillions in debt to fight the pandemic; what are long term implications of taking on that much debt?

A: When contemplating the implications of massive government debt accumulation, two things must be remembered. The first, learned in the years after the Great Recession, is that trying austerity – raising taxes and cutting spending – in the midst of a deep downturn is doomed to failure, as the shrinking economy drives up the debt-to-GDP ratio. The second is that when the inflation adjusted real interest rate is less than the growth rate of the economy, then a much bigger debt load can be sustained. As of mid-August, the ten year real interest rate is -1%. The longer term growth rate for the US economy is about 2%. So, the better question would be – what would be the consequences of trying to avoid building up debt load during the recession by not spending? Likely, the outcome would be much worse.

– Menzie Chinn, professor, La Follette School of Public Affairs, economics

Q: Is it safe to swim in an indoor pool?  

A: Physical distancing and masking is challenging in that setting, so the risk [of contracting COVID-19] is higher at an indoor swimming pool than in other settings.

– Nasia Safdar,  professor, University of Wisconsin School of Medicine and Public Health, Medical Director of Infection Control at UW Hospital and Clinics  

See more answers to COVID questions at Also, visit our COVID-19 impact site.