Direct Wire vs. Hardwired Ionization Smoke Alarms

Alarm Power Types

• Direct wire and hard-wired ionization smoke alarms refer to the same type of alarm. The terms "direct wire" and "hard-wired" are used interchangeably for citing the alarm's power source. These alarm types are directly connected to a home's electrical supply. The only other smoke alarm alternative to the direct or hard-wired alarm is the battery-powered type. Batteries must be placed in the alarm periodically for a functional unit.

Ionization Functioning

• The direct or hard-wired alarm uses ionization science for detecting smoke. Electrically charged plates within the alarm ionize, or convert, air molecules passing through its assembly, generating a current flow. Interruptions to the current flow, such as smoke, activates the smoke alarm with loud, piercing chirps or horns.

Ionization Benefits and Drawbacks

• False alarms do not occur from steam or dust particles entering the alarm assembly but rapid flame fires with minimal smoke are easily detected with the ionization technology. Ionization alarms are less expensive compared to photoelectric, or optical, alarms. However, small, smoldering fires are more difficult to detect, possibly spreading before the ionization technology reacts with an alarm. Smoke from cooking can falsely activate the alarm. Consumers should also be aware that ionization alarms use radioactive material for the ionization current flow function.

Interconnection

• Many consumers choose direct or hard-wired smoke alarms because of their interconnection ability. Multiple alarms within a home connect together through the home's electrical supply. When one alarm detects smoke and sounds an alarm, all of the alarms will sound simultaneously. This function is especially helpful during sleep. For example, an alarm sounding in the bedroom will wake inhabitants in the middle of the night to a fire detected in the kitchen. Battery-powered smoke alarms cannot connect to one another, regardless if they are ionization or photoelectric versions.

Safety

• Although direct or hard-wired smoke alarms do not require periodic battery replacements, consumers should test the smoke alarm system on a monthly basis. Each alarm should have a test button. Pressing the test button should activate the alarm, as well as any interconnected alarms within the system.