Objective  To investigate and evaluate the cabin air quality of domestic flights in China.

Methods  The parameters of cabin temperature, relative humidity, wind speed, air pressure, illuminance, noise, carbon monoxide, carbon dioxide, and total numbers of airborne bacteria and fungi of different aircraft types were monitored with convenience sampling. The distribution of the parameters detected during cruising for different aircraft types and different positions and the correlation between the parameters were statistically analyzed.

Results  For the 56 flights investigated, the average cabin temperature was 23.7 ℃, with the average relative humidity being 34.5%, the average air pressure being 84.9 kPa, the median wind speed being 0.07 m/s, the average noise value being 72.1 dB(A), the median illuminance being 141 lx, the average carbon monoxide concentration being 0.124 mg/m³, the average carbon dioxide concentration being 0.11%, the median total number of airborne bacteria being 2 per dish, and the median total number of airborne fungi being 1 per dish. The cabin wind speed of medium aircrafts was significantly higher than that of large aircrafts (P < 0.05), and the other parameters were not significantly different between different aircraft types (P>0.05). The cabins in the middle had a significantly lower carbon dioxide concentration and significantly higher noise level and wind speed than those at the front and the back (P < 0.05), with no significant differences in the other parameters (P>0.05). Humidity was insignificantly correlated with the total numbers of bacteria and fungi (P>0.05). Wind speed was significantly correlated with carbon dioxide concentrations (P < 0.05), and not significantly correlated with humidity (P>0.05).

Conclusion  The sampling survey showed that the level of cabin air quality of domestic flights is good in terms of most parameters, but there are still issues including low humidity and high noise levels, compromising the comfort of passengers and aircrew, although they usually do not affect flight safety. In addition, some parameters are different for different positions and aircraft types. An appropriate increase in wind speed can effectively reduce carbon dioxide concentrations. At present, civil aircraft cabin air quality is an important part of aviation environmental health, but there is no unified industry standard or specification for its monitoring. This study can provide a reference and data support for the formulation of civil aircraft cabin air quality standards and monitoring method.