pyestock | your guess is as good as mine

To the back of the control room, and traversing the whole building north-south was another corridor, which we quickly dubbed the "brown corridor" on account of its appalling utilitarian colour scheme. Yet another random image from random websites was now anchored firmly in my mind. Interestingly, for Pyestock, all the heavy duty doors to the west remained locked and padlocked. Normally wed have found a key (as they were plentiful and well labelled) but one of the doors was open. Inside it was strangely dark and a breeze whipped through the open grilled vent in the floor. To the south, I immediately recognised an air filter, having seen one very similar at RAF Wyton. This bank of parallel rooms were obviously where air was sucked into the Air House passing through all these air filters.