The air was somewhat drier but also of higher 'quality' because less of it was recirculated; most was fresh intake from the atmosphere, heated, passed through the cabin and dumped.

The introduction of widebody twins in the early 1980s coincided with increased air recirculation, in order to reduce bleed-air load on the engines, and until the 787 and A380 it was often over 60% recirculated.

Ironically the elimination of smoking led to a big increase in recirculated air.