In early 2020 there was a Covid outbreak in an air-conditioned restaurant in Guangzhou, China. A study about this specific outbreak concluded that,“droplet transmission was prompted by air-conditioned ventilation.” A subsequent study recommended avoiding re-circulated air and maximizing outdoor air supply in buildings. Then the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) produced a guidance document for re-opening schools and universities. However, one key fact remains: there is less risk of Covid transmission outdoors than indoors.
We can safely conclude that there is less risk outdoors, because most Covid transmissions have taken place indoors, and there has only been a limited number of outdoor transmission cases, as per Ian Hanomansing’s informative tweet.
This knowledge should be driving our public policy. Specifically, in the following areas:
- University and school classes need to be outdoors (weather permitting) or better yet completely online,
- Bars and restaurants need to have open windows or preferably patio seating, and
- Employers may need to upgrade their ventilation systems and implement engineering controls.
On a personal note, it was sad to see Brothers Food & Wine permanently closed. I have wonderful memories of spending time there with family. However, it was admirable to see the owners of Brothers recognize that it would not be responsible to reopen a locale which did not lend itself to physical distancing.
Likewise, we must all do our part during this pandemic and whenever possible take our activities outdoors. If outdoors is not an option nor is staying at home, employers and educational institutions must rely on professional advice to implement risk mitigation measures, such as engineering controls, personal protection equipment, physical distancing and upgrading of ventilation systems.
High Park Engineer 