Yet it is a little appreciated fact that many of us at home, school, and work breathe air containing CO2 concentrations of 1,000 ppm every day.

A 2012 study concluded that at “1,000 ppm CO2, compared with 600 ppm, performance was significantly diminished on six of nine metrics of decision-making performance.” At 2,500 ppm, performance levels became more or less “dysfunctional.”

Jean started cracking his bedroom door open at night, and saw the average CO2 level drop by 500 ppm.