We recommend purchasing a major brand from an established hardware or home supply source. Make sure you get alarms with the label of a recognized testing laboratory. Save and always follow the manufacturer’s instructions.
A smoke alarm with a PHOTOELECTRIC sensor is better at detecting slow, smoldering fires, while a smoke alarm with an IONIZATION sensor is better at detecting fast-flaming fires. An alarm with both types of sensors is called a DUAL SENSOR alarm. We recommend your home has at least one of each kind (ionization vs. photoelectric), and get as many dual sensor alarms as you can. The National Fire Protection Association (NFPA) has more useful information on these alarm types.
Also, if you have any gas appliances, you should have at least one carbon monoxide alarm on every level of your home. You may choose to get a COMBINATION alarm that can detect both smoke and carbon monoxide.
The best protection comes from alarms that are HARD-WIRED (also known as INTERCONNECTED), meaning they are tied into your electricity with a battery back-up. When one hard-wired alarm sounds in your home, they all sound! Most homes built since the 1990s have hard-wired alarms.
