[BroadHopper]

Codes varies from town to town. Laconia requires a smoke detector on every floor preferably in the hallway. I have rental property in Hooksett. The Hooksett codes requires a smoke detector in the Bedroom hallway, a heat detector in the Kitchen area. If you have gas applinces, A CO detector should be located near the floor where the appliance. If you have a cellar the CO detector should be located in the cellar. Hooksett requires hard wiring.
As for rental property HUD federal requiements is a smoke detector on all floors including cellar if you have one. The federal requirements almost always contrdict local codes.

Call your fire dept for code requrements. They will even come inspect your house as to proper placement.