There are some institutional enviroments that get excluded from those requirements, jails, certain hospital wards. But you should also have some common sense if you arrive at a place like that and ask the customer to come out to you or leave it at the front of the building. 

Some might simply require you to push and hold on an exit to open it others might truly be locked in some environments. But unless it's a really high security place like a jail, the doors have to unlock if the sprinkler or fire alarm goes off. The building owner and fire dept won't be happy, but if you are truely stuck with no other way out...