All homes need smoke alarms.
There should be units in all bedrooms and on all floors with at least one in every large area. 
Near the furnace and fireplace are other good locations. You cannot have too many smoke alarms.
All smoke alarms are not the same!
Ionization Alarms are the older type.
They are very good at detecting smoke from burning toast but slow to detect a house fire.
Photoelectric Alarms are the newer type.
These do not false alarm with toast and have a very fast reaction time to a house fire smoke. These should be your choice.
they can be hardwired or for homes without alarm hard-wiring they are available with a radio link between the alarms, if one goes off, they will all alarm.
They are also available with a built in Carbon Monoxide detector, or as a dual unit with ionization and photoelectric sensors so it can detect fast and slow-burning fires.
Do not place smoke alarms in the kitchen where they tend to false alarm all too often, place them in an adjacent room.
