CO密度: 1.250 g/L at 0 °C, 1 atm, 1.145 g/L at 25 °C, 1 atm, 

 空氣密度: 1.292 g/L  at 0 °C, 1 atm, 1.184 g/L at 25 °C, 1 atm, 

因為1 ppm = 1mg/kg

所以at 25 °C, 1 atm

1 ppm = 1 mg/(1kg/(1.292 kg/m^3)) = 1.292 mg/m^3 = 1.292 mg /(1.250 kg/m^3)/m^3 = 1.034e-6 atm

1 mg/m^3 = 0.774 ppm

1.0e-6 atm = 0.967 ppm