A smoke detector can be the difference between life and death.

This smoke detector two-pack from First Alert packs a one-two punch.

First Alert’s 9120B Smoke Detector brings quick protection to your home.

Kidde’s combo smoke alarm also protects against carbon monoxide.

According to the National Fire Protection Association (NFPA), around two-thirds of home fire deaths happen in spaces without a smoke detector. It takes minutes for a fire to fill your home with thick black smoke. The critical warning they provide can mean the difference between life and death. If your detectors are broken or very old, you should take the time to replace them. Luckily, even the best smoke detectors are affordable and easy to install.

A smoke detector, or “smoke alarm,” senses the presence of smoke and blasts a loud alarm in response. While they vary in size and shape, household models typically feature plastic enclosures and are mounted high on a wall or ceiling.

Though smoke detectors seem ubiquitous and interchangeable, manufacturers use a couple of different methods to make them:

Photoelectric smoke detectors trigger an alarm when smoke enters a chamber and reflects light onto a sensor. They protect better against slow, smoldering fires than fast, raging fires. 

Ionization smoke detectors feature a sensor with a small amount of radioactive material between two electrically charged plates. When smoke enters the chamber, the flow of ions becomes disrupted, activating the alarm. Ionization-type detectors are generally better at identifying fast-burning flaming fires.

Both photoelectric- and ionization-style detectors have advantages and disadvantages, so there is no one obvious choice. For comprehensive coverage, the NFPA recommends using both kinds in your home. Some devices feature both technologies in a single device.

We recommend placing your smoke detectors based on their expertise. Use photoelectric detectors near stoves and outside of bathrooms, where smoke may accumulate over time from a small fire. Put ionization-style units in areas where fires are less likely to start, so they can catch fast-moving flames.

I’ve been renting an apartment with my wife (and dog) for nearly 10 years and, during that time, I replaced our old smoke detector with something new. I regularly test the detector to ensure it’s in working order, and I also monitor the condition of our major appliances, wall heater, and fireplace for potential fire risk. These are just a few small steps necessary in a more comprehensive fire safety plan, which also includes a fire extinguisher and escape route.

When I’m not obsessing over my family’s safety, I’m writing about gadgets and gear for publications like Popular Science, CNN Underscored, and TechnoBuffalo. To make these selections, I consulted fire safety guides from health and safety organizations, including NFPA.org, Ready.gov, and RedCross.org. I also reviewed PopSci’s previous coverage on the best practices for fire safety and consulted expert reviews.

You shouldn’t have to think too much about your smoke detectors. A great one should be easy to install, take little effort to maintain, and accurately alert you when there’s an emergency. After installing a smoke detector, you shouldn’t even notice it’s there (unless it goes off). We considered dozens of options to find the best smoke detector. These factors separated the good detectors from the bad ones.

The first and most important thing to look for in a smoke detector is a certification from Underwriters Laboratories, the safety science company that sets standards for equipment like smoke and carbon monoxide detectors. All smoke detector manufacturers must meet the company’s most recent standard for smoke alarms, ANSI/UL 217, to place a UL certification on their products. Essentially, the “UL Listed” seal of approval tells you that a detector has been tested to meet strict requirements, and will work as advertised. 

In addition to sensor technology, smoke detectors vary based on how they receive power. Most detectors rely on disposable batteries but hardwired models that you wire into your home’s power are also an option.

Battery-powered smoke detectors—which usually rely on disposable 9-volt, AA, or lithium cells—offer flexible placement. You can easily install one in any room in your home at any time. They also require slightly more maintenance, as you need to replace their batteries annually to ensure they’re operational. It’s important to note that manufacturers advise against using rechargeable batteries in smoke detectors, as they lose their charge more quickly and have a shorter runtime than standard disposable batteries.

Alternatively, some battery-powered detectors come with sealed-in lithium batteries designed to last 10 years, making it so you never have to worry about replacing a battery. Some states, including California, require you to use this kind of detector to prevent people from taking the batteries out when the alarm goes off. Check your state and city ordinances for the best guidance on what’s required in your area.

Other smoke detectors are designed to get hardwired into your home’s electrical system. This makes it so you’ll never have to replace a battery to keep them operational. That said, installing them is a much more time-intensive process and includes working with electrical wiring. If you purchase a hardwired detector, make sure to buy one that features a backup battery, which will keep your detectors on if your house loses power.

If you need to protect a large home with multiple floors, it helps to buy a set of “interconnected” smoke detectors that can sync with each other so that if one detector senses smoke, all of your alarms will go off. In the event of a serious, fast-moving fire, this will ensure that everyone in your home knows to get outside as quickly as possible.

Most smoke detectors are relatively basic devices, but there are some newer “smart” models with internet-enabled features. These detectors will often sync up with a mobile app, allowing you to check their status and mute them from your phone. The app also can give you a warning before the alarm goes off, giving you a small window to silence it if you’re cooking or already know it’s a false alarm. Some even offer voice alerts and can tell you which detector senses smoke.

Smoke detectors are extremely important for every home. If you haven’t replaced yours in the past 10 years, it’s time to buy a new set. The best detectors are affordable, reliable, and easy to install. More importantly, they’ll provide fire protection and peace of mind for you and your family.

Why it made the cut: The First Alert SA511CN2-3ST packs powerful interconnectivity and voice alerts to let you know when there’s a fire.

The First Alert SA511CN2-3ST hits all the basic marks we look for in a smoke detector. This UL-Listed photoelectric model features interconnectivity, so you can connect up to 18 smoke alarms across your home. You can also assign it with one of 11 pre-set home locations, so its voice alert can tell you where the smoke is coming from.

Since it is designed to work as part of a larger set, we’re recommending a two-pack of detectors to make it a little more affordable if you decide to replace a full set of smoke detectors. That said, you can always get an individual model as well.

Why it made the cut: The First Alert 9210B Smoke Detector supports interconnectivity, an easily accessible test/mute button, and a 9-volt backup battery system.

The First Alert 9120B Smoke Detector is a hardwired ionization unit that features a single test/mute button and a 9-volt battery backup system. It can also act as part of an interconnected, multi-unit alarm system of up to 12 First Alert smoke detectors, so you have more comprehensive coverage in your home. The 9120B also features a dust cover to keep particles from getting in, a mounting bracket lock for tamper resistance, and smart technology designed to reduce false and “nuisance” alarms. 

Why it made the cut: If you don’t already own a carbon monoxide detector, Kidde’s combination smoke/CO alarm has you covered.

Kidde’s combination smoke and carbon monoxide alarm is an excellent option if you need to install both smoke and carbon monoxide detectors. The battery-powered combination alarm constantly monitors your home for both smoke and gas, providing specific voice alerts if danger is present. (It also calls out “low battery” when it’s time to replace its 9-volt power source.) Kidde’s combination alarm also features a convenient hush/test button and a battery compartment on the front, making it easy to perform an annual battery change.

Why it made the cut: With a slim profile and long-lasting battery, the First Alert PR710 Slim is a great way to protect your home.

If your home is too old for a hardwired smoke alarm, but you don’t want to ever change a battery, the First Alert PR710 Slim is a solid photoelectric smoke detector with a sealed lithium-ion battery guaranteed to last 10 years. Its thin, low-profile design is no-frills—just a single test/mute button and that’s it. Unlike many of our other picks, it uses a classic siren, rather than voice alerts. It also cannot sync with other alarms. All in all, it’s a great option for apartments and other small spaces where you just need one smoke alarm, and you’d prefer to buy a new smoke detector every ten years than replace a set of batteries every few months.

Why it made the cut: The Nest Protect by Google provides a multitude of smart features in addition to smoke and CO detection.

The Google Nest Protect offers traditional smoke and carbon monoxide monitoring, with several convenient smart features. Chief among them, you receive a direct alert through the Nest smartphone when it detects danger. You can also conveniently mute the alarm through that alert. The Protect features a specialized photoelectric “Split-Spectrum” sensor, which uses two LED lights to detect a wider range of smoke particles. According to Google, the Split-Spectrum Sensor adds all the benefits of Ionization smoke detectors, without drawbacks like false alarms (or buying two types of smoke detectors).

Of course, the downside here is that the Nest Protect costs a lot more than any other smoke detector. In many cases, you can buy three standard photoelectric detectors for the price of one Nest Protect. It may be a convenient upgrade if you already have Nest gear at home, but it’s paying a pretty penny for the privilege.

Why it made the cut: The Kidde Smoke Detector is simple, affordable, and offers powerful interconnectivity.

If you’re already planning to get some electrical work done, this Kidde Smoke Detector is a very affordable hardwired smoke detector with a battery backup. It looks simple but can sync with up to 24 safety devices, including up to 18 smoke alarms. In addition to a hush/test button on the front, Kidde’s smoke detector also features a tamper-resistant locking pin, a low battery indicator, and a flashing LED, so you know it’s working. Conveniently, the unit also features a front-facing battery door, so you can easily replace the 9-volt battery. Small features like this can make a big difference, particularly if you’re in a space with multiple alarms.

The U.S. Fire Administration and National Fire Protection Association recommend replacing the batteries in your smoke alarms at least once per year. With a 10-year lithium battery, you should replace the detector when the battery gets low. In either case, you should test your alarms once per month to make sure they’re working properly.

You should consult the manufacturer’s instructions when replacing your smoke detector. In general, smoke alarms should be replaced every 10 years. This will ensure you always have a unit that works properly and meets modern safety standards.

It may sound like overkill, but the U.S. Fire Administration recommends you place a smoke detector inside and outside each bedroom and sleeping area. You should also have at least one smoke alarm on every level of your home to ensure every corner is covered. Remember, you only have a few minutes before conditions in your space become untenable from a raging fire, so it’s essential to have as early a warning as possible. An early warning could provide you with precious time to respond accordingly.

Everyone triggers a smoke alarm while cooking every once in a while. While “nuisance alarms” like these are annoying, so you shouldn’t take the battery out of your detector. When a smoky kitchen threatens to set off the detector, press the alarm’s hush button and open nearby doors or windows. Then wave a towel at the alarm to help clear the air. You can also temporarily move the alarm away from your kitchen, but remember to move it back when the smoke clears.

A house fire can spread quickly, so every second counts. An early warning from a smoke detector can be the difference between life and death. If your home isn’t properly outfitted with detectors, you should take the time to install them. Your safety depends on it.

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