Many main entrance doors to a block of flats, for example, have a basic Yale nightlatch or similar fitted. While this is convenient for the tenants it fails to meet two criteria…
Meeting insurance approved security levels
Allowing for easy fire escape in emergencies
A standard Yale type nightlatch arrangement is easy to use but also vulnerable to being picked/slipped or bypassed by people who should not be entering (non-keyholders). If you want to improve the security of the lock a BS3621 nightlatch can be fitted. It features an armoured cylinder escutcheon and automatically deadlocking latchbolt when the door is closed. However these nightlatches also have the ability to have the inner handle deadlocked with the key, stopping it from being operated if someone smashes the glass.
This is fine for a domestic property but totally unsuitable for a communal entrance door.
The reason is that in the event of an emergency the residents need to escape quickly. It can potentially be fatal if someone has locked the inner handle, as without the key it cannot be unlocked and therefore allow the lock/door to be opened and escape made. You cannot have the residents being forced to go back into their smoke filled flat, for example, to find a key in their panic.
So Yale make a version specifically to cater for this requirement. Depending on the size of the lock it is called the PBS3 or PBS4. The British Standards these locks adhere to is BS8621 (as opposed to BS3621 for the lockable version). Here is a picture of a PBS4 fitted by Linacre locksmiths.
The inner handle has no keyway so cannot be deadlocked – fire escape regulations will always override security. The safe evacuation of residents is always the first concern.
So if you are concerned what is fitted to your own communal doorway, or if a landlord looking to check you have the right lock in place, give Linacre Locksmiths a call and we can give the correct advice. http://www.linacrelocksmiths.com