I noticed that in a Walmart supercenter, the ceilings were about 20 feet high. The place was crowded with chatting, loitering goons, and it felt like a tropical reptile exhibit building in a zoo (humid, stuffy). There’s no ventilation because of the company’s policy for keeping heating and cooling bills low, security (doors closed), etc. The place reeked of bad breath, perfume and B.O.
In those places, I wear my N-95, and get in and out ASAP.