Hi, 

Can you install a thumb turn lock in a stairwell door (emergency escape route). I didn’t think you could but some of the staff in the office want the lock installed.  There is no lock at door at the moment. So would a push bar be better option?

Depending on who will be using the door (staff/public, under/over 60 persons) you should use either a BSEN 179 emergency exit device (https://www.safelincs.co.uk/emergency-bolts-and-push-pads/) or BSEN 1125 panic exit device (https://www.safelincs.co.uk/panic-bars-with-latches-or-bolts/)