Even 1000 ppm is pretty high in practice. In offices it approaches this value, and it's no wonder that one needs pharma-strength stimulants and intense exercise

Even 1000 ppm is pretty high in practice. In offices it approaches this value, and it's no wonder that one needs pharma-strength stimulants and intense exercise to survive the day in the office. Ever wonder why one feels sleepy in meeting rooms: it's because the CO2 is approaching 2000. At home I like it below 600 ppm, with values between 600 and 800 leading to a gradual deterioration of mental interest. Once it goes above 800, then in the absence of pharma stimulants, the harm to cognition is quickly apparent. I'd be willing to bet that the value for optimal cognition could be closer to 200 ppm which would be close to its per-industrial value.