Introduction
The First Alert SMI100 Battery-Operated Smoke Alarm is designed to provide early warning of smoke and fire. Equipped with First Alert's Precision Detection advanced sensing technology, it aims to reduce nuisance alarms while ensuring timely alerts in a home fire emergency. This manual provides essential information for the proper installation, operation, and maintenance of your smoke alarm.
Important Safety Information
Please read and understand all instructions before installing and operating your smoke alarm. This alarm is designed for residential use only. Failure to follow these instructions may result in property damage, injury, or death.
- Do not paint the smoke alarm. Paint can clog the sensing chambers and prevent the alarm from operating properly.
- Do not install in areas with high humidity, extreme temperatures, or excessive dust.
- Test your smoke alarm weekly to ensure it is functioning correctly.
- Never ignore a smoke alarm. Investigate the cause of the alarm and take appropriate action.
- Replace the smoke alarm unit at least every 10 years from the date of manufacture.
Package Contents
Verify that all items are present in your package:
- First Alert SMI100 Smoke Alarm Unit
- Mounting Bracket
- Mounting Screws and Anchors
- 9V Alkaline Battery
- User Manual (this document)

The smoke alarm is shown alongside its mounting plate and included screws, illustrating the components needed for installation.
Setup and Installation
The SMI100 smoke alarm is designed for easy installation. Follow these steps for proper setup:
- Choose a Location: Install smoke alarms on every level of your home, including basements and in every bedroom. For optimal protection, place alarms in hallways outside of sleeping areas. Avoid placing alarms near windows, doors, or air ducts where drafts might interfere with smoke detection.
- Install the Battery: The SMI100 features a front-access battery compartment for easy installation and replacement. Open the battery compartment and insert the included 9V alkaline battery, matching the positive (+) and negative (-) terminals correctly. Close the compartment securely.
- Mount the Alarm:
- Mark the location for the mounting bracket on the ceiling or wall.
- Drill holes and insert the plastic anchors if necessary.
- Attach the mounting bracket using the provided screws.
- Align the smoke alarm with the mounting bracket and twist clockwise until it locks into place.
- Test the Alarm: After installation, press and hold the Test/Silence button on the front of the alarm until you hear a loud, piercing alarm sound. This confirms the unit is functioning correctly.

This diagram illustrates optimal locations for smoke alarms and carbon monoxide alarms throughout a typical home, including bedrooms, hallways, living rooms, kitchens, basements, and garages.

The smoke alarm features a convenient front access battery compartment, simplifying battery replacement without needing to remove the unit from its mounting.
Product Overview Video
This video provides a comprehensive overview of the First Alert SMI100 Smoke Alarm, including its features and basic operation. This video is provided by the seller.
Operating Instructions
Your First Alert SMI100 Smoke Alarm is designed for simple operation:
- Normal Operation: The power indicator light (LED) will flash approximately once every 40-60 seconds to indicate that the smoke alarm is receiving power and functioning correctly.
- Alarm Condition: When smoke is detected, the alarm will sound a loud, continuous siren. The LED will flash rapidly.
- Silence Feature: In case of a nuisance alarm (e.g., from cooking smoke), press the Test/Silence button. This will temporarily silence the alarm for approximately 10 minutes. The alarm will automatically reset after this period if the smoke has cleared. If smoke is still present, the alarm will reactivate.
- Testing the Alarm: Test your smoke alarm weekly by pressing and holding the Test/Silence button until the alarm sounds. Release the button once the alarm sounds.

A person is shown pressing the test button on a ceiling-mounted smoke alarm, demonstrating regular testing procedure.
Maintenance
Regular maintenance ensures your smoke alarm remains in optimal working condition:
- Battery Replacement: When the 9V battery is low, the alarm will chirp approximately once every minute. Replace the battery immediately. Use only a 9V alkaline battery. The front access battery compartment makes this process simple.
- Cleaning: Clean your smoke alarm at least once a month. Use a soft brush or vacuum cleaner with a soft brush attachment to remove dust and debris from the alarm's vents. Do not use cleaning solvents or spray directly onto the alarm.
- End-of-Life Warning: The alarm has a lifespan of approximately 10 years. After 10 years from the date of manufacture, the unit will emit an end-of-life warning chirp (usually 5 chirps every minute). This indicates it's time to replace the entire smoke alarm unit.

A woman holds a smoke alarm, illustrating the importance of replacing units at least every 10 years for optimal safety.
Troubleshooting
If your smoke alarm is not functioning as expected, refer to the following common issues and solutions:
| Problem | Possible Cause | Solution |
|---|---|---|
| Alarm chirps once every minute. | Low battery. | Replace the 9V alkaline battery immediately. |
| Alarm chirps 5 times every minute. | End-of-life warning. | Replace the entire smoke alarm unit. |
| Alarm sounds frequently without smoke. | Dust or debris in the sensing chamber, high humidity, or cooking fumes. | Clean the alarm as described in the Maintenance section. Use the Silence button for nuisance alarms. Relocate if consistently triggered by cooking. |
| Alarm does not sound during test. | No battery, dead battery, or faulty unit. | Ensure battery is installed correctly and is fresh. If problem persists, replace the unit. |
If you continue to experience issues, please contact First Alert customer support.
Specifications
| Feature | Detail |
|---|---|
| Brand | First Alert |
| Model Number | SMI100 |
| Power Source | Battery Powered (9V Alkaline) |
| Sensor Type | Ionization |
| Color | White |
| Product Dimensions | 5.4"D x 5.4"W x 1.9"H |
| Item Weight | 0.7 Pounds (11.2 ounces) |
| Included Components | 9V Alkaline Battery |
| Manufacturer | Resideo |
| Country of Origin | Mexico |
Warranty and Support
For warranty information or technical support, please contact First Alert customer service. You can typically find contact details on the manufacturer's website or on the product packaging.
Visit the official First Alert Store for more information: First Alert Store





