thanks everyone, that makes a lot more sense.
I thought that the location for the welding room was decided back in December, so didn’t really expect practical objections along these lines right now. But I understand the concerns.
this looks useful: https://www.hse.gov.uk/pubns/guidance/wl2.pdf
I don’t know exactly how you define “confined space”. It could well be the case that every part of the Hackspace is confined in some way.
I don’t know (and I literally mean I don’t know – I’d like to be told differently) why local exhaust ventilation (LEV) isn’t sufficient for welding. You remove fume at the source, and as long as the room isn’t sealed, air will be drawn in from elsewhere in the space. Gases and fumes shouldn’t accumulate or seep into other rooms as they are removed at source.