VIP 16: Air quality in passenger aircraft

This VIP focuses on best practice, as well as challenges, for the conditioning of the indoor environment in passenger aircraft cabins, and their implications from a ventilation stand-point.
This article is based largely on findings from EU’s FP5 project “CabinAir”.
In early commercial jet aircraft, passenger cabins were ventilated with 100 % outside air. In more recent jet aircraft, approximately 50 % of the ventilation air is outside air and the remaining 50 % is filtered recirculated cabin air.
This development has allowed for fuel savings as well as a supposed improvement in the relative humidity of cabin air.
With typical passenger densities in modern airline cabins employing partial recirculation of cabin air, however, carbon dioxide concentrations have been shown to exceed 1000 ppmv (parts-permillion by volume) in some sections of the cabin on some flights.
This has raised the question of whether air quality and ventilation are acceptable in modern jet airliner cabins.