On Monday, May 18, 2020 at 7:46:10 AM UTC+1, wrote:
Brian Gaff (Sofa) explained :
I do remember we had a clean air room at one place I worked and most of the
dust was removed by a surface at high voltage which was continuously swept
into some kind of receptacle, and the filters seemed to last a long time, but
then this was a very large room and we are talking three industrial sized
units here.

Leeds University had a high voltage / plenum system for their
refectory, back in the 1960's.

Leeds Uni Refectory? Ah, happy days ... some of the sweatiest, noisiest, most
enjoyable gigs of my life were experienced there, in the 80's. I confess I
didn't experience the air as being very pure at that time...

Jon N