Every house should have several smoke alarms. There should be a smoke alarm in every bed room so that when a fire occurs the person in the room is more likely to be woken up. Besides having an alarm in every room there should be at least one alarm on every level of the house and in the kitchen.
Alarms should be tested every month. This is done easily but pushing the test alarm button. If the alarm is not working properly try to change the batteries. The batteries should be changed every time there is a time change, so twice a year.
When testing alarms make sure that everyone in the building knows where to go in case of a fire. Practice getting them to location safely. Also, it is good to have the alarms set off at night once to see if everyone in the house wakes up. If it does not wake everyone up you may want to look in to placing more alarms in the house.
Smoke alarms are not very expensive and some fire departments even give out smoke alarms because an alarm is the first way to get a person notified of smoke in the house, which in an indicator of fire.