Churches crammed with religious folk are a thing of the past in Western-Europe today, but not so in the 1930's.
A lot of people in a closed locale wasn't too pleasant before aftershave and deodorant were prolific among the masses.
So mediating smelly arm-pits and pongy feet in summer through the use of ventilation became a hot topic.
Ventilation in silent-running mode of course. Acoustics was/is a big issue in church buildings and extra noises were/are to be avoided.
Numerous are the articles on how d.i.y.-priests could tackle noisy pipes in their own House of God.
A cross-section drawing of a ventilation-installation show a possible set-up for expelling the foul air. There is a preference expressed that it be vacated through the bell tower if at all possible.
However there is not a mention on how fresh air is to be pumped into the church.
My guess is the priest would be hunting down whistling doors from drafts in the building instead of poltergeist-like banging sounds in his plumbing system.