Reuter’s discusses a study which shows that the more outside air inside a building, the less germs in the air.

The Swiss know that. They’ve known it for years. When I was living there back in ’82 (22 years ago), one office building had not opened because the owners had ordered it with a/c. To the builders that meant the windows wouldn’t open. To the workers that meant the environment would be alive with germs. So no one had gone to work. They had to re-do the building so the windows would open. I think they also took out the a/c.