Ozone measurements in jet airliner cabin air

Ozone measured in cabin air on 14 flights over polar areas shows maximum concentrations during Spring. Ozone numbers close to atmospheric values were found in the air entering the cabin through the air conditioning system but a reduction to about half of this value takes place immediately within the cabin air. Aircraft with recirculating cabin air showed an additional reduction by about 25%. Maximum concentrations are considerably higher and the duration of such periods longer than those reported in FAA Technical Report ADS-5 in which, however, data from polar areas during O₃ maximum are missing. Ozone destruction effects within the pressurization system as claimed in the FAA report are doubtful. Although O₃ reduction occurs within the cabin air, the threshold value of 0.1 ppm. for breathing air was surpassed in about 75 % of the flight time (8 to 10 hr between Copenhagen and Seattle) and maximum concentrations (0.4 ppm during 4 hr and 0.6 ppm during 1 hr) were found to be close to critical values recommended by the Environmental Protection Agency. Assuming that no O₃ destruction takes place in the pressurization system, O₃ concentrations exceeding 1 ppm, can be expected to enter the cabin at flight levels for commercial flight on polar routes during Spring. Some experiences during periods of high O₃ concentrations were increasing irritation in the eyes and the respiratory tract, effects different from those associated with low humidity in cabin air.