In-person events pose a risk of Covid transmission for attendees, but how much? It depends on a large variety of factors, from the size of the meeting space to attendees’ mask fabric. A new website allows meeting organizers to plug in 14 event variables to get a quantitative estimate of the risk in their unique circumstances.
The tool, COVID-19 Indoor Safety Guideline, was developed by researchers at the Massachusetts Institute of Technology and posted in November. It considers the event from several angles:
Room specifications: square footage, ceiling height, the type of air ventilation and filtration systems, the air-recirculation rate, and the relative humidity in the space.
Behavior of attendees: exertion level (resting, standing, light exercise, etc.), respiratory activity (normal breathing, whispering, loud talking, singing, etc.), the quality of attendees’ masks (for example, a one-layer cotton mask is 50 percent efficient whereas a disposable surgical mask is 90 percent efficient), and the compliance with wearing them.
The system also asks about the kind of space (classroom, restaurant, etc.), how much time will be spent there, the risk tolerance of the group, and, of course, the number of attendees in that space.
Based on your variables, the MIT site returns information on how many people can be in the space safely for a certain length of time. For example, in a 1,000-square-foot room with a 12-foot ceiling and moderate ventilation and air filtration, where attendees are standing and talking while wearing multi-layer cotton masks (with 85 percent of attendees well fitted and complying with mask rules), the six-foot distancing guideline would limit occupancy to 27 people and, according to the tool, the group would no longer be safe after two hours. Interestingly, using one-layer cotton masks would shorten that window dramatically, making the group unsafe after only 59 minutes.
The site does not take into consideration the destination where the meeting is taking place, but planners looking for more data can continue their research using a Covid Risk Assessment Planning Tool created at the Georgia Institute of Technology that looks at group risk based on U.S. location and event size.