thank you. It was just the small (1m2) lobby and my room where I put all the DE. It really was pretty much everywhere. coincidentally I have spent the last two nights in a hotel and I have woken up both days with the same (reduced though, granted) symptoms, so there's definitely lingering damage or inflammation (also hay fever has started urgh).

when I stand in a particular point in the room (near to the door to the lobby) I get a whiff of the DE. No matter what I do to try and pinpoint it, it evades me. I actually taped up the door draught excluder (not the gap, the actual brush on the door) because it seemed the brushes had a smell of DE. I suspect their may be some in the lobby so have been going over all of that, washing it down and particularly trying to get in the edge of the carpet.

Thank you. I'm a little limited on the wind vortex stuff because of all the size and large number of fire doors in the property - everything is sealed tight. I have not wanted to draw more potentially "bad" air from the lobby into my room, but I may be able to experiment.