Indoor air quality: recommendations relevant to aircraft passenger cabins

To evaluate the human component of aircraft cabin air quality the effects of respiration of a resting adult on air quality in an enclosed space are estimated using standard equations. Results are illustrated for different air volumes per person, with zero air exchange, and with various air change rates. Calculated ventilation rates required to achieve a specified air quality for a wide range of conditions based on theory agree to within 2% of the requirements determined using a standard empirical formula. These calculations quantitatively confirm that the air changes per hour per person necessary for ventilation of an enclosed space vary inversely with the volume of the enclosed space. However, they also establish that the ventilation required to achieve a target carbon dioxide concentration in the air of an enclosed space with a resting adult remains the same regardless of the volume of the enclosed space. Concentration equilibria resulting from the interaction of the respiration of a resting adult with various ventilation conditions are compared with the rated air exchange rates of samples of current passenger aircraft, both with and without air recirculation capability. Aircraft cabin carbon dioxide concentrations calculated from the published ventilation ratings are found to be intermediate to these sets of results obtained by actual measurement. These findings are used to arrive at recommendations for aircraft builders and operators to help improve aircraft cabin air quality at minimum cost. Passenger responses are suggested to help improve their comfort and decrease their exposure to disease transmission, particularly on long flights.