First Alert Combination Smoke & Carbon Monoxide Alarm, Battery Operated Detector with Test & Silence Button, SMCO100, 1-Pack,White

Why I chose this combo alarm

I replaced an aging single-purpose detector in my hallway with First Alert’s combo alarm to simplify my setup: one device for both smoke and carbon monoxide. I wanted something easy to mount, battery powered, and less prone to nuisance chirps and false alarms from the kitchen. The SMCO100 checked those boxes and promised “Precision Detection” that complies with newer standards aimed at cutting down on cooking-related alarms. After several weeks of use—and a few intentional tests—I’m comfortable saying this is a solid, no-drama safety upgrade for most homes.

Design and build

The alarm is a plain, low-profile white puck that blends into a ceiling or high wall without attracting attention. The face features a prominent test/silence button you can press without reaching for a pin or paperclip, and status LEDs that remain unobtrusive until you need them. The battery compartment is tucked away, and the mounting plate locks in with a satisfying click. Nothing about the build feels flimsy, and the overall fit and finish are what I expect from a major safety brand.

Small touches help in day-to-day use. The test/silence button is easy to find by feel, which matters when an alarm goes off at 2 a.m. and you’re trying to confirm whether it’s a real event or not. The unit also includes an end-of-life warning so you’ll know when it’s time to replace the alarm rather than guessing at its age.

Installation and setup

Installation is straightforward:

• Choose a location: ceiling or high on a wall, away from corners and vents. I placed mine in the hallway just outside the kitchen to cover bedrooms and common spaces while minimizing cooking-triggered alarms.
• Attach the mounting plate with two screws/anchors.
• Insert the batteries, align the marks, and twist the alarm onto the plate until it locks.
• Press the test button to confirm the alarm is working.

Because it’s battery operated, there’s no wiring and no pairing. Setup took me under ten minutes, including drilling pilot holes. If you’re replacing an old unit, take a moment to write the installation date on the label—makes maintenance and eventual replacement a lot easier.

Placement tip: keep smoke alarms at least 10 feet from cooking appliances to reduce nuisance trips. Avoid bathrooms where steam can cause false alarms, and don’t put them right next to supply vents or windows that can disrupt airflow.

Performance and false-alarm behavior

The headliner here is First Alert’s Precision Detection, designed to meet updated standards that aim to reduce nuisance activations from normal cooking. I tested the unit with a can of UL-rated smoke test aerosol and with some decidedly overdone toast. The alarm responded quickly to the aerosol test (as it should), and it did not trip during typical stovetop simmering or while my oven preheated with the door cracked—a win for day-to-day sanity. When I went out of my way to burn toast, it eventually sounded as expected. That’s exactly the balance you want: tolerant of minor cooking plumes but decisive when actual smoke is present.

I can’t simulate a carbon monoxide leak at home, but the built-in test function checks the sensor circuitry and sounder. The siren is undeniably loud—piercing enough to jolt someone awake from down the hall. Distinct alarm patterns and a status LED help differentiate conditions so you can tell at a glance whether the unit is complaining about smoke, carbon monoxide, a low battery, or end of life.

Everyday usability

• Test/silence: The front button works reliably. A quick press triggers the test; a press during a nuisance alarm silences it temporarily. I’ve used it mid-cook to quiet the unit without disabling protection entirely.
• Battery life and alerts: The alarm will chirp periodically for a low battery, and it provides a separate end-of-life message when the sensing elements have aged out. That distinction matters; it prevents unnecessary battery swaps when it’s actually time for replacement.
• Maintenance: Like all smoke/CO alarms, it benefits from monthly testing and a quick vacuum pass with a soft brush to clear dust.

What I like

• Two-in-one coverage: One unit handles smoke and carbon monoxide, simplifying placement and maintenance.
• Fewer nuisance alarms: In my setup, it has been appropriately resistant to routine kitchen activity while still reacting promptly to genuine test smoke.
• Loud, attention-grabbing siren: You can hear it through closed doors and across a floor, which is the point.
• Simple, tool-light install: Battery power and a twist-on plate make it a quick upgrade for renters and homeowners alike.
• Practical controls: A big test/silence button and clear status indications keep interaction simple.
• Replacement clarity: End-of-life warning reduces guesswork about when to retire the unit.

Where it falls short

• No interconnect: This model doesn’t wirelessly or physically interconnect with other alarms. If you want every alarm in the house to sound when one goes off, you’ll need an interconnected system or a different model.
• No smart features: There’s no app, no phone notifications, and no voice announcements. Some households will prefer the simplicity; others might want remote alerts or a digital CO readout.
• Battery maintenance: Battery-powered alarms are only as reliable as the batteries in them. If you’d rather not manage that, consider a sealed 10-year battery model or a hardwired unit with battery backup.

None of these are deal-breakers for the SMCO100’s core mission, but they do shape who it’s best for.

Who it’s for

• Renters and condo owners who want a quick, reversible safety upgrade without touching electrical wiring.
• Older homes that lack hardwired detectors and need reliable smoke and CO coverage across multiple rooms.
• Secondary spaces—garages, workshops, guest rooms, or home offices—where a simple, standalone alarm makes sense.
• Homeowners who prioritize reduced cooking nuisance alarms near kitchens or open-plan living areas.

If you’re outfitting a larger home, I’d still recommend a layered approach: place smoke alarms in every bedroom, outside sleeping areas, and on every level; add at least one CO alarm on each level and near sleeping areas. This combo unit is a strong candidate for the hallways and common areas in that plan.

Safety notes and best practices

• Test once a month using the front button.
• Vacuum the unit every few months to keep dust out of the sensing chamber.
• Replace the batteries when the unit chirps for low power; don’t ignore it or remove batteries as a “fix.”
• Pay attention to the end-of-life warning and replace the unit promptly when it arrives.
• Follow local codes for placement and quantity—requirements vary by jurisdiction and home layout.

Value and the bottom line

In a market crowded with feature-heavy “smart” alarms and bare-bones budget models, this First Alert combo alarm strikes a practical balance. It’s dependable, easy to live with, and designed to cut down on the most common pain point—false alarms from routine cooking—without compromising response to real risks. While it lacks interconnectivity and app support, the fundamentals are strong: accurate detection, loud alerts, straightforward maintenance, and simple installation.

Recommendation: I recommend the First Alert combo alarm for anyone who wants reliable, two-in-one smoke and carbon monoxide protection with minimal hassle. It’s particularly well-suited to apartments, smaller homes, and retrofit scenarios where running new wires isn’t feasible. If whole-home interconnectivity or smart notifications are must-haves, look at networked or app-enabled alternatives. For everyone else, this model delivers exactly what a safety device should: consistent performance, clear alerts, and fewer false alarms—without making you think about it day to day.