1. Introducción
This manual provides essential information for the installation, operation, and maintenance of your First Alert 9120B Hardwired Smoke Alarm. This device is designed to provide early warning of smoke and fire hazards in residential environments.
Las características principales incluyen:
- Ionization Sensor: Detects smoke from fast-flaming fires.
- Cableado con respaldo de batería: Garantiza un funcionamiento continuo incluso durante cortes de energía.tages using a 9-volt battery.
- Interconectividad: Can be linked with compatible BRK or First Alert alarms, causing all connected alarms to sound when one is triggered.
- Alarma de 85 decibeles: Provides a loud alert upon smoke detection.
- Botón de prueba/silencio: Allows for easy testing of alarm functions and silencing of nuisance alarms.
- Latching Alarm Indicator: Identifies the initiating alarm unit after an event.
- Señal de fin de vida: Notifies you when the unit needs replacement.

Image 1.1: First Alert 9120B Hardwired Smoke Alarm. This image shows the front view of the smoke alarm with its test/silence button and speaker grille.
2. Información de seguridad
Please read and understand all instructions before installing and operating this smoke alarm. Keep this manual for future reference.
- Seguridad eléctrica: Installation involves electrical wiring. Ensure power is turned off at the circuit breaker before beginning installation. If you are unsure about electrical wiring, consult a qualified electrician.
- Wiring Polarity: Confirm correct wiring polarity and secure all wire nut connections. A loose neutral (white wire) connection within the home junction box can cause device malfunction.
- Copia de seguridad de la batería: The 9-volt battery backup is crucial for operation during power failures. Ensure a fresh battery is installed and replaced annually.
- Colocación: Install smoke alarms on every level of your home and in each bedroom for optimal protection.
- Pruebas: Pruebe la alarma de humo semanalmente para garantizar su correcto funcionamiento.
3. Contenido del paquete
Su paquete debe contener los siguientes artículos:
- First Alert 9120B Hardwired Smoke Alarm Unit
- Soporte de montaje
- Mazo de cables
- Batería 9-Volt
- Manual de instrucciones
Note: This product is typically sold in multi-packs (e.g., 6-pack), meaning you will receive multiple sets of the above items.
4. Configuración e instalación
Follow these steps for proper installation of your hardwired smoke alarm:
- Apagar la energía: Before starting, turn off the power to the circuit where you will be installing the smoke alarm at your main electrical panel.
- Retire la alarma antigua (si corresponde): If replacing an existing alarm, carefully remove it and its mounting bracket. Disconnect the wiring harness.
- Preparar el cableado: Connect the new wiring harness to your household wiring. Typically, this involves connecting:
- Black wire (hot) to black wire
- White wire (neutral) to white wire
- Red/Orange wire (interconnect) to red/orange wire (if interconnecting multiple alarms)
- Instale el soporte de montaje: Secure the universal mounting bracket to the electrical junction box using the provided screws.
- Instale la batería: Open the side-load battery compartment and insert the 9-volt battery, observing the correct polarity. Close the compartment.
- Conecte la unidad de alarma: Connect the alarm unit to the wiring harness. Align the alarm unit with the mounting bracket and twist clockwise until it locks securely into place.
- Restaurar energía: Turn the power back on at the circuit breaker. The alarm should chirp once and the power indicator light should illuminate.
- Alarma de prueba: Press and hold the Test/Silence button until the alarm sounds. This confirms proper operation.
Colocación recomendada
For optimal safety, follow these placement guidelines:
- Instale al menos una alarma de humo en cada nivel de su casa, incluido el sótano.
- Install a smoke alarm inside every bedroom.
- Install a smoke alarm in the hallway outside of each sleeping area.
- Avoid placing alarms near windows, doors, or forced-air vents where drafts could interfere with smoke detection.
- Keep alarms away from cooking appliances to prevent nuisance alarms.

Image 4.1: Recommended Smoke Alarm Placement. This diagram illustrates ideal locations for smoke alarms, carbon monoxide alarms, and fire extinguishers throughout a typical home, including bedrooms, hallways, living room, kitchen, basement, and garage.
5. Instrucciones de funcionamiento
Prueba de la alarma
Test your smoke alarm weekly to ensure it is functioning correctly:
- Press and hold the Test/Silence button firmly for a few seconds.
- The alarm will sound a loud, pulsating horn. This indicates the electronic circuitry, horn, and battery are working.
- Suelte el botón. La alarma se detendrá.
Si la alarma no suena durante la prueba, consulte la sección Solución de problemas.
Silenciamiento de alarmas molestas
If a non-emergency situation (e.g., cooking smoke) triggers the alarm, you can temporarily silence it:
- Press the Test/Silence button briefly.
- The alarm will enter a temporary silence mode for approximately 10 minutes.
- The alarm will automatically reset after the silence period if the smoke condition has cleared. If smoke is still present, the alarm will reactivate.
Indicadores de alarma
- Power/Alarm LED: A red LED light indicates the status of the alarm. It flashes periodically during normal operation and rapidly during an alarm condition.
- Alarma de bloqueo: If multiple interconnected alarms are present, the unit that initiated the alarm will have its red LED flash rapidly, while other interconnected alarms will sound but their LEDs will not flash as quickly. This helps identify the source of the alarm.
6. Mantenimiento
Reemplazo de batería
The 9-volt battery should be replaced at least once a year, or immediately when the low battery chirp sounds. The alarm will chirp approximately once every minute to indicate a low battery.
- Turn off power to the alarm at the circuit breaker.
- Gire la alarma en sentido antihorario para quitarla del soporte de montaje.
- Abra el compartimento de la batería.
- Remove the old 9-volt battery and dispose of it properly.
- Insert a new 9-volt battery, ensuring correct polarity.
- Cierre el compartimento de la batería.
- Reattach the alarm to the mounting bracket by twisting clockwise until secure.
- Restore power at the circuit breaker and test the alarm.
Limpiar su detector de humo
Clean your smoke alarm at least once a month to remove dust and debris that can interfere with its operation:
- Turn off power to the alarm at the circuit breaker.
- Remove the alarm from its mounting bracket.
- Use a soft brush attachment on your vacuum cleaner to gently vacuum the alarm's cover and vents.
- Do not paint the alarm. Paint can clog the openings and interfere with the sensor's ability to detect smoke.
- Reinstall the alarm, restore power, and test.
Señal de fin de vida útil
The smoke alarm is designed to provide reliable protection for approximately 10 years. After this period, the unit will emit an end-of-life signal (typically a chirp every 30-40 seconds) to indicate it needs to be replaced. Replace the entire unit immediately upon hearing this signal.
7. Solución de problemas
| Problema | Posible causa | Solución |
|---|---|---|
| La alarma no suena durante la prueba. | No power, dead battery, or faulty unit. | Check circuit breaker. Replace 9-volt battery. Ensure alarm is properly connected to wiring harness and mounting bracket. If issues persist, replace unit. |
| Alarm chirps once a minute. | Batería baja. | Reemplace la batería de 9 voltios inmediatamente. |
| La alarma suena cada 30-40 segundos. | End-of-life signal. | Reemplace toda la unidad de alarma de humo. |
| Alarmas molestas (falsas alarmas). | Cooking smoke, steam, dust, high humidity, or insect infestation. | Press the Test/Silence button. Ventilate the area. Clean the alarm. Relocate the alarm if it's consistently triggered by non-fire sources. |
| Alarm malfunctions or behaves erratically. | Loose neutral wire connection. | Apague la energía en el disyuntor. Check all wire nut connections, especially the white (neutral) wire, in the home junction box to ensure they are secure. If unsure, consult a qualified electrician. |
8. Especificaciones
| Característica | Especificación |
|---|---|
| Número de modelo | 9120B |
| Fuente de poder | 120 V CA cableado con batería de respaldo de 9 V |
| Tipo de sensor | Ionización |
| Volumen de la alarma | 85 dB a 10 pies |
| Humedad de funcionamiento | 10-95 % HR (sin condensación) |
| Temperatura de funcionamiento | 40 °F (4.4 °C) a 100 °F (37.8 °C) |
| Dimensiones (D x W x H) | 1.9" x 5.6" x 5.6" |
| Color | Blanco |
| Material | Plástico |
| Certificaciones | Listado por UL |
9. Garantía y soporte
Información de garantía
This First Alert 9120B Smoke Alarm comes with a 10-year limited warranty. For specific terms and conditions, please refer to the warranty documentation included with your product or visit the official First Alert websitio.
Atención al cliente
For technical assistance, troubleshooting, or warranty claims, please contact First Alert customer support. Contact information can typically be found on the product packaging or the official First Alert websitio.





