Photoelectric alarms are exempt from this requirement. Smoke detectors for fire alarm systems do not require the hush feature and ten-year battery, either. Ionization smoke alarms contain material that ionizes the air, making an electrical path. When products of combustion enter the device, the molecules attach themselves to the ions. The change in electric current flow triggers the alarm.
Photoelectric alarms contain a light source and photocell, which is activated by light.
Light from the bulb reflects off the smoke particles and is directed towards the photocell. The photocell is then activated to trigger the alarm. When properly installed and maintained both types of alarms will save lives. Apartments are required to have smoke alarms as per the building code at the time of construction. However, there are minimum requirements for all buildings.