Tom,
AnthonyB has summed it up very succinctly but you still seem to be missing the point. I might have a small pub, say, with eight exit doors. But it can only hold 100 people at the very most, so my fire risk assessor has told me I need two fire exits. I choose one at the front and one at the back, I sign them up, provide appropriate emergency lighting covering the routes to them (probably don't put break glass call points or extinguishers by them because it's a pub) and the other six exits I can do whatever I like with - deadlock them, padlock them, paint them pink, hide them behind curtains, keep man-eating dogs behind them, etc.
I am not compelled to choose between the two extremes that you suggest - either providing them with opening mechanisms suitable for fire exits or bricking them up.
Stu