Thank you very much for your reply.
I was thinking that case, and I am almos sure that you are right. But it is like that it seems that the Coordinator will be saturated if all the sensor of occupancy in the several rooms detect someone at close moments.
So, I have read that a cluster tree can be divided in different cluster heads, where the routers are called Cluster Head, so.. I have the doubt if this Cluster Head are still acting as a router, as you explained before, or they can make decisions, for example:
In the same room, the sensor devices check that someone is there, so the end device transmitt that to the Cluster Head of this room and that one to the other end device which turns on the light. (without going thourgh all the tree until the PAN coordinator).