Why we install Fire Alarm Conduites As Embeded at normal rooms / offices < while we install it Expossed at corridors / lobbies?

You can install it exposed in the rooms too.

Thats not mandatory to be embedded

It is a general practice to install fire alarm conduites exposed even in rooms as well becasue they need multiple joints in the future. They are preffered in corridors because of more danger of fire in corridors.

in carridors it might be subject for extentions or new connections thats why

We can not install it in the rooms because it is no need to increas cost , that we have to decreas ,EMT is5 times expensive than pvc.