I just had a moderately long conversation with a distributor of these UV-C products. Theirs, once the safety is tripped (ie: the PIR) they will not re-energize until the whole fixture is reset. So, indeed, they Latch off to prevent the "sleeping person" scenario. They also recommend the use of timer switches to only apply power in the early hours of the morning, or when manually overridden. (eg: clear the auditorium between shows and manually "blast" it.) One thing to watch out for is rooms like control rooms that are not a part of the auditorium, technically, but have windows into it. Any kind of interlock would need to take that into account. I'm not sure what, if any UV-C attenuation is offered by regular glass. The units I was looking at are good for about 40M2 each, with about a 100 degree "beam", so probably OK to be mounted at 6 metres and permitted to overlap each other to reach the required dose. (That also helps with the shadowing problem.) Auditoria with finished ceiling might have a challenge but I could see them working in an "exposed services and catwalks" kind of room. One other thing to watch is the maximum effective range of the movement sensors they come equipped with. Cost was comparable to mid-range fixed LED fixtures, around $1000-$2000 / fixture. (That's about 600 -1200 quid in old money. ;)) However, one big unknown: How they interact with the fabrics they will be shining on. We all know how bad sun-bleached theatrical drapes get - so a big concern for me would be the longevity of the seats / drapes in the treated area.