Smoke alarms are like having a spare tire in a car: you may never need or use it, but no one should drive a vehicle without a fully inflated spare tire. Most smoke and carbon monoxide alarms only need a battery to operate, but there are hard wired models as well. There currently are combination models that serve for both purposes, and many with a 10 year lithium ion battery. It appears these products have become more sophisticated and, therefore, seem to be more reliable. You can purchase some models that are interconnected so when one senses a problem all of them go off; newer models can be purchased that do not “chirp,” but actually have a voice alarm, and yet others have a strobe light that flashes as a warning.
Remember, it is important to use the “test” button on a regular basis and to change the battery at least one time a year unless you feel at ease with those that the manufacturer designates a 5 or 10 year battery. In addition, you should select the best date you will remember to change the battery, such as holiday (July 4th, Thanksgiving or New Years’ day, etc.). These products also have to be clean; and, when dust and debris accumulates, the alarm may not work or be delayed to the point it is not safe. All of the above factors help make your residence safer even if no smoking is allowed &/or you have a newer home.