I had a monitor with me on an international flight recently. Once with hit our cruising altitude, co2 was only 800 ppm. Higher than you might want, but lower th

I had a monitor with me on an international flight recently. Once with hit our cruising altitude, co2 was only 800 ppm. Higher than you might want, but lower than a lot of office buildings. Humidity, however, was 10%, and the cabin pressure would also have been lower than at ground level.