How to cheaply ensure good ventilation and air filtration in a large room with many people?

 This is a prerequisite for allowing those people to work together, minimizing the chance of getting coronavirus infection. 

 "Experts agree that good ventilation is the most effective and practical way to rid a space of contaminants. The Healthy Buildings program recommends four to six air exchanges per hour in classrooms, through any combination of ventilation and filtration.

New York City mandated every classroom have at least one operable window to help with ventilation, even in the winter. So let’s see what happens when we open a window.

We managed to achieve four total air exchanges by opening just one window in this simulation, which was dependent on specific weather conditions. To get to six air exchanges, we will have to do more.

Let’s try adding a simple air cleaner with a HEPA filter and a box fan blowing fresh air into the room, both practical and low-cost options.

With the window open, the concentration remains densest near the infected student, but the contaminants are diluted in the rest of the room. Exposure for the other students is reduced.

And with an air cleaner and a fan, the overall concentration levels are at their lowest. The contaminants are concentrated at the front of the room where the fan is blowing, and diluted everywhere else.

The Healthy Buildings guidelines call for a fan blowing out the window, not in. “We don’t want to ever blow air across anyone’s face, not knowing who’s infected,” Dr. Allen said.

And since our open window and fan were in the front of the room, we placed our air cleaner in the back for balance. When you don’t know the airflow patterns, it’s generally best to put it in the center of the room."