As long as someone remembers to turn on the HVAC, a button by the door of each classroom, the HVAC pulls in fresh outside air. The Church will not tell us if they are using MERV13, but we have word from an EQ president, the Church is only using MERV8

CO2 remains below 800 ppm with up to 12 people in the classroom when the HVAC is on. When it is off, 12 people can bring the levels close to 2000 ppm in short order.

We have no readings yet of a full classroom.