To test a smoke alarm, first station someone at the furthest point away from the alarm, and then hold the test button on the smoke detector. Because smoke alarms are typically loud, it is best to alert family members before testing; this avoids causing any disturbances or upsetting small children. Having someone stationed at the furthest point in the home away from the alarm makes sure the noise can be heard in all parts of the home.
After holding the test button on the alarm, a loud siren should begin to sound, although it takes a few seconds to do so on some models. A weak or nonexistent siren indicates that the batteries need to be replaced. As a general rule, batteries should be replaced every six months.
Another way to test a smoke alarm is by using real smoke. To do this, light a match and blow the smoke directly under the alarm. Keep in mind that it may take a little longer for the detector to register the smoke and sound the siren (compared to the test button method). If the smoke alarm is out of reach, then an aerosol can of smoke sprayed at the alarm allows for testing.