The real hazard is when you're on the ground. I've seen cabin C02 levels above 3000ppm when the cabin air handling hasn't been turned on! I'll take my mask off

The real hazard is when you're on the ground. I've seen cabin C02 levels above 3000ppm when the cabin air handling hasn't been turned on! I'll take my mask off to eat/drink in the air, which I didn't do the one time I had to fly mid-pandemic.