First Alert SMCO210, 10-Year Sealed Battery Combination Smoke & Carbon Monoxide Alarm with Slim Profile Design, 1-Pack

Why I chose this combo alarm

Aging 9V smoke detectors and a standalone CO alarm in my home meant batteries to replace, chirps at inconvenient hours, and a patchwork of devices on the ceiling. I wanted something simpler and more modern: a single, reliable unit that covered both smoke and carbon monoxide, with a battery I wouldn’t be thinking about every year. That put the First Alert SMCO210 on my shortlist. After living with a few of them installed around the house, here’s how they performed and what I learned.

Install and setup

Setup is straightforward. The base plate mounts with two screws, and the alarm twists on to activate the sealed battery. No wiring, no pairing, no app. I installed one outside the bedrooms on the hallway ceiling, one in the basement near the HVAC and water heater, and another in a large living area. The included instructions are clear and emphasize proper placement: not too close to vents or bathrooms, a reasonable distance from kitchens, and on the ceiling or high on a wall.

Total time per unit was under five minutes, including marking and drilling. I appreciated that the alarm ships dormant and only powers up when you lock it onto the base; you can handle the install without it beeping at you. I labeled each alarm with install date and room location—helpful a decade down the road.

Design and usability

The slim profile is the first thing you notice. It sits much closer to the ceiling than older pucks and looks tidy. The face has a single, easy-to-find button for test and hush, and a small status LED. The plastic feels solid, and the twist-on motion to the base is positive and secure. It’s not a design piece—you won’t admire it—but it blends in and doesn’t call attention to itself, which, for a life safety device, is the right goal.

The silence/test button is responsive. Monthly testing takes a couple of seconds of press-and-hold, and the indicator light behaves as expected during normal operation and while testing. I keep a step stool handy for testing, though in one hallway I can reach the button with a long-handled tool.

Sensing performance in daily life

First Alert’s “Precision Detection” is designed to meet updated industry standards and reduce cooking-related false alarms. In practice, I found the SMCO210 to be well-behaved around normal cooking. Basic sautéing and baking didn’t set it off, even with the hallway unit 15 feet from the kitchen. It handled toast and oven preheats without complaint.

I tried to provoke it with a controlled “burnt toast” scenario and a smoky pan. It sounded as expected when visible smoke made its way down the hall, and it responded quickly. The hush function worked after I cleared air and ventilated the space; a momentary press quieted the alarm while the room returned to normal. That’s how I want an alarm to behave: tolerant of everyday steam and minor cooking smoke, responsive when there’s sustained smoke.

For CO detection, I didn’t simulate a dangerous scenario (nor should anyone). My evaluation here relies on regular testing via the button and placement best practices—one unit near potential CO sources and one near sleeping areas. Given First Alert’s track record and compliance with modern standards, I’m comfortable with it covering both risks in a single housing.

Nuisance alarms and placement tips

No alarm is entirely immune to nuisance triggers. I learned two things that improved my results:

• Keep it out of the steamy bathroom plume: Steam can look like smoke to a sensor. Moving a hallway unit a couple of feet farther from a bathroom door eliminated occasional steam-induced alerts after hot showers.
• Mind the kitchen distance: Even with the improved sensing, placing an alarm too close to the stove is asking for false alarms. The manufacturer’s distance recommendations are worth following.

The hush feature is useful but not magic. If there’s sustained smoke, the alarm will re-sound, which is the correct behavior. Also note: you cannot “pull the battery” to silence it—it’s sealed. If a unit is sounding and won’t hush, ventilate and resolve the source; if the unit is malfunctioning, you’ll need to deactivate and replace it.

Battery and service life

The sealed 10-year battery is the main reason to consider this model. In exchange for a slightly higher upfront cost, you get a decade of power without battery swaps—and no low-battery chirps at 3 a.m. That’s a relief. There’s an end-of-life warning when it reaches the end of service, reminding you to replace the entire alarm. That’s standard for sealed units.

A small quirk of sealed-battery devices is that if a unit fails prematurely, you can’t fix it with a battery change; the whole alarm needs replacement. That’s the trade-off for convenience. Because of that, I suggest labeling install dates and keeping the purchase info handy.

Maintenance

Even “maintenance-free” alarms benefit from simple care:

• Test monthly using the button.
• Vacuum the exterior every few months to keep dust from the sensor inlets.
• Avoid painting over it or blocking airflow.
• Replace at 10 years (or sooner if the end-of-life signal appears).

These steps take minutes but help avoid nuisance behavior and ensure the unit remains responsive.

What it doesn’t do

A few features you won’t get here:

• No interconnection: These aren’t hardwired or wireless-interconnected. If one sounds, the others don’t follow. If you have a larger home or want alarms that talk to each other, you’ll need a different model.
• No smart features: There’s no app, no phone notifications, no self-testing reports. For some homes, simplicity is ideal; others might prefer connected options.
• No replaceable battery: By design. You’re trading replaceable batteries for long-term convenience.

None of these are deal-breakers in a straightforward setup, but they’re worth noting before you commit.

Value

On a per-unit basis, the SMCO210 costs more than basic 9V smoke detectors and standalone CO alarms. Over a decade, the math evens out once you add annual batteries and time climbing ladders. For me, the “set it and forget it” factor, reduced nuisance triggers, and single-unit coverage made the value proposition strong.

If you’re outfitting a whole home, the cost bumps up quickly. I’d love to see better multi-pack pricing, but in terms of long-term ownership costs, this still lands in a reasonable place—particularly for rental units or for anyone who can’t easily maintain ceiling-mounted devices.

Everyday experience

After install, the best compliment I can give a safety device is that I stop thinking about it. These have been quiet during normal life, loud when tested, and unobtrusive on the ceiling. The slim profile is genuinely nicer than older, bulky designs. The dual protection simplifies planning, especially in hallways where space is at a premium.

The only adjustment I made was moving one unit slightly farther from a bathroom to eliminate steam interactions. Beyond that, the experience has been uneventful—in the good way.

Who it’s for

• Homeowners and renters who want straightforward, dual protection without wiring.
• Landlords equipping units where simple install and long service life reduce maintenance calls.
• Anyone tired of ladder climbs for battery changes.

Who might look elsewhere:

• Those who need interconnected alarms for larger homes or specific code requirements.
• Users who want app alerts or integration with a smart home platform.
• People who prefer replaceable-battery units to handle rare device failures without replacing the whole alarm.

Recommendation

I recommend the SMCO210 for most households that want reliable, low-maintenance protection against both smoke and carbon monoxide. The slim design looks better than older alarms, installation is simple, and the sealed 10-year battery eliminates routine battery changes and low-battery chirps. In daily use, it’s appropriately calm around normal cooking and decisive when there’s sustained smoke, and the end-of-life alert makes replacement planning clear.

It’s not the right pick if you need interconnected or smart features, and the sealed battery means a rare device failure requires full replacement. But as a straightforward, modern combo alarm with thoughtful sensing to cut down on nuisance triggers, it’s a strong, practical choice.