The 5 best smoke detectors we tested in 2021

The best smoke detector overall

The X-Sense SC01 features a 10-year lithium battery, carbon monoxide detector, and a color-changing LED to let you know its current status.

Pros: Digital battery level display, doubles as carbon monoxide detector 

Cons: Lacks ionization sensor 

The X-Sense SC01 responded well in my testing and activated its alarm within two sprays of the aerosol. It had a loud alarm that was clearly heard from across the 2,700 square foot house I tested it in, and its red LED flashed continuously while the alarm was sounding. The alarm — and the light — shut off simultaneously when the sensor no longer detected any aerosol. 

The X-Sense SC01 lacks an ionization sensor and uses only a photoelectric sensor to detect smoke. This makes it marginally less sensitive to flash fires, but also cuts down on the chances of it being set off by nuisance alarms, or false alarms caused by cooking smoke or steamy showers. Its screen displays the real-time amount of carbon monoxide in the air, the status of the unit during a test, and a battery level icon.

Installing the X-Sense SC01 was simple, and with a power drill and pencil, I was able to attach it to the ceiling in about two minutes. The anchors are white, so they blended in with the ceiling, and also came in a resealable plastic baggie, which was convenient.

Overall, the value of the 10-year battery, the carbon monoxide detector, and digital readout make it the best option I tested. The detector also comes highly recommended by our fire investigator expert.

The best smart smoke detector

The Nest Protect features both a carbon monoxide and split-spectrum smoke detector that detects both fast and slow-burning fires, and delivers clear verbal instructions to explain why its sensor was triggered and what you should do next.

Pros: Spoken instructions, phone notifications

Cons: May not be ideal for those not technically savvy, requires three AA backup batteries

The color-changing LED, along with the verbal commands and smartphone notifications, made the Nest Protect fun to test out and operate. My first aerosol test activated its “heads-up” function, which issued a verbal warning that it detected a small amount of smoke. This would be a convenient feature if the smoke was due to burning toast, or another non-emergency — especially for anyone who might get overwhelmed by loud noises. By giving you the chance to resolve the problem before the smoke levels rise, you can prevent the unit from going into full-blown alarm mode. My second aerosol spray was enough for the Nest Protect to assume there was an actual fire, and it sounded its alarm immediately. 

The Nest Protect allows you to silence the unit in the event of a nuisance alarm easily with the large and easy to press test/silence button. You can even silence the alarm from your smartphone, although it doesn’t allow for this if the smoke is too heavy.

The Nest Protect is a hard-wired unit, so installation was a bit more elaborate than the other smoke detectors I tested. This will involve working with and reconnecting electrical wiring, so if you’re uncomfortable around that type of thing, you may want to hire a professional. It took me about 15 minutes to remove the previous unit and connect this one. The instructions walked me through every step of the process, and the included hardware was effective and easy to use. It also took me about 15 minutes to connect the Nest Protect to my home’s Wi-Fi network due to connection issues. 

If your home Wi-Fi goes down like in the event of a power outage, the Nest Protect will continue to work just fine — you just won’t get any notifications on your phone. The three AA batteries will ensure the Nest Protect continues to work during a power outage.

The best smoke detector for smoke only

If you already have a standalone carbon monoxide detector, the X-Sense SD01 is a dependable smoke-detector-only that uses an extra-bright LED to help lead you to safety. 

Pros: Ultra-bright escape light, easy to install, auto-monitoring feature

Cons: Lacks a carbon monoxide detector

The X-Sense SD01 has a nice solid feel to it and the large LED escape light gives it a professional look, like something you would see in a commercial building. This light automatically turns on when the alarm is activated, and not only alerts you about the presence of smoke but can also help to illuminate a darkened room. This is an especially important feature as more than half of home fire-related deaths occur between 11 p.m. and 7 a.m., according to the NFPA. This light would also be extremely valuable in the event of a power outage, a feature that Andler praised and why he endorses the X-Sense SD01 so strongly.  

This unit responded well to my tests and activated after two aerosol sprays. I made sure to perform one of my tests at night to best observe the escape light and was very impressed with how bright it was. The light, the loud alarm, and a flashing red secondary LED would be effective in the case of a real emergency. These high-visibility features also make the X-Sense SD01 a great option for hallways and stairwells as long as you have one or two on the ceiling as well. 

The X-Sense SD01 packs a built-in 10-year battery, so it will last for the life of the unit, and after you’ll need to purchase an entirely new alarm. It’s also designed to constantly auto-check itself to make sure its batteries are in working order. In the event of an issue, the secondary LED will turn yellow, alerting you that something is wrong. 

The X-Sense SD01 uses a photoelectric sensor, which works with the air flow design of the casing to better detect a variety of fire types. The sensor also analyzes smoke three times before activating the alarm, which minimizes nuisance alarms. 

Installing the X-Sense SD01 was a breeze, just like the other X-Sense models, and I had the mounting plate installed and the unit in place within a couple of minutes. 

The best dual sensor smoke detector

The First Alert SA320 is an affordable and effective smoke alarm with both photosensitive and ionization sensors, which can cause it to be too sensitive at times. However, there’s no denying its effectiveness.

Pros: Has both photosensitive and ionization sensors, has safety features suitable for landlords 

Cons: Very sensitive, batteries must be replaced regularly

The First Alert SA320 features both photosensitive and ionization sensors, which is likely the reason why it was the only unit that activated its alarm after a single aerosol spray test. 

Although this high sensitivity sounds good on paper, it can also be the cause of frequent nuisance alarms. These alarms, combined with the removable AA batteries, greatly increase the odds that someone will remove the batteries or the alarm itself. The NFPA reported that between 2009-2013, 21% percent of deaths in home fires occurred when smoke detectors were “present but did not operate.” It’s important to keep this in mind if you’re planning to get this unit — after all, the whole point of a smoke detector is household safety.

I didn’t experience any issues installing the First Alert SA320. But, it uses red wall anchors, which aren’t ideal if you want to move the unit to a different location in the room. It also has optional locking features to discourage unauthorized battery or alarm removal. There are two pins you can insert into the sides of the unit or by the battery compartment that expand once they’re in place to prevent anyone from taking down the smoke detector or removing its batteries. You “unlock” the unit with a flathead screwdriver to depress the pin’s teeth. This is a good feature for landlords, or anyone else placing the unit who won’t be there to monitor it. 

The First Alert SA320’s design makes it feel more functional and less clunky. It does lack the polished appeal of the X-Sense models, though it shouldn’t be a big factor compared with safety and effectiveness. Andler describes this as “a standard smoke detector at a good cost.”

The best interconnected smoke detector

The X-Sense Wireless Interconnected comes as a set of six separate smoke detectors with a range of more than 820 feet each, so they can cover small and large spaces safely.

Pros: Small size is easy to install, easy to find silence button in the dark, covers large areas

Cons: Does not have a built-in battery 

Even though the X-Sense Wireless Interconnected smoke detectors are smaller and lighter than typical ones, they still meet UL 217 standards. They also beeped at the same 85-db level as every other model tested. Their red alert lights were easy to see, and because of their side-mounted position, they reflected off the ceiling to increase visibility.  

Because they are interconnected, all six units will sound even if only one detects smoke, so you’ll be notified regardless of where you are in your home when a fire breaks out. They performed effectively in every test I did and were all relatively sensitive, responding within two aerosol sprays. Since the silence button is also the alert light, it was easy to quickly find the button to silence the unit — even in low light. 

Each unit was interconnected right out of the box, so there was no additional set up necessary. You can add up to 24 units to the network, but every new set will need to be manually connected to the rest. This process seems pretty straightforward though, and X-Sense’s instructions are clear, ensuring this process won’t be too complicated.

Installation of the six-pack took longer than other smoke detectors I tested because there were more units to install. Their small size only required two anchor holes per unit, as opposed to the three that the other units I tested needed. This not only made them easier to install but also reduced the amount of damage to the ceiling and walls. Each of the units easily clicked onto its mounting bracket and they were the simplest to install out of all smoke detectors I tested. Like all X-Sense models, their smooth finish gave them a nice, high-quality look. 

What else we tested

What else we recommend and why 

After researching a dozen smoke detectors, we ended up testing six that met our criteria for units you could install yourself. Here’s what else we tested and think are worth considering:

First Alert PRC710 ($49.99): The First Alert PRC710 responded well to my tests, and I really liked its slim 1.38-inch profile and light 0.73-lb weight. Although I personally preferred the informative LED screen of the X-Sense SC01, if you’re simply looking for a minimal, hassle-free unit that detects both smoke and carbon monoxide, the First Alert PRC710 is an effective choice. 

What we’re testing next

A few smoke detectors didn’t arrive on time for me to test, so I look forward to testing them soon. We’re also researching smoke detectors for people who are hard of hearing. 

First Alert BRK 3120B: This hardwired version of the First Alert SA320 includes both photoelectric and ionization sensors, and usually costs under $25, the lowest of any unit I’ve tested. 

Kidde KN-COSM-IBA: Kidde is one of the most well-known smoke alarm brands out there, and it offers a really wide variety of detector types, styles, and sensor options. This model features voice warning capabilities, a feature I’ve found to be really useful with other smoke detectors I tested. 

First Alert Onelink: I’m interested in how the First Alert Onelink and its smart capabilities will stack up against the Nest Protect. 

Testing methodology

For this guide, I personally tested six smoke detectors after consulting with fire and building experts, and doing extensive online research. 

I interviewed Patrick Andler, a fire investigator with 38 years of experience and a board member of the Arizona Burn Foundation. This organization — among many other functions — supplies free smoke detectors to low-income housing across Arizona. I also interviewed Nick Yahoodain, a home remodeler with more than 11 years of experience at Advanced Builders & Contractors. 

I also used my own experience installing hard-wired and battery-powered smoke detectors in my own apartments and my parents’ home, as well as my experience as a residential carpenter, which frequently required the relocation of hard-wired units.

I installed each of the smoke detectors and tested it three times a day for three days. I performed a basic maintenance test according to the manufacturer’s instructions (usually just by pressing the “test” button) and then sprayed the units twice with an aerosol spray that mimics real smoke. Most smoke detectors will not activate after a single spray so you will need two three-second sprays to set them off. I found this to be the case with every unit I tested, except for the First Alert SA320, which activated its alarm after only a single spray.  

I broke these tests up throughout the day to allow time for the spray to dissipate and the detectors to return to their working levels.  

I used several criteria to compare the units during testing. 

Installation: I installed each smoke detector on my ceiling according to the manufacturer’s included instructions, timing how long it took, and noting how helpful or detailed those instructions were. Aside from the hardwired First Alert, all the units used essentially the exact same mounting procedure, but I made sure to note any differences. 

Appearance: I took note of the size, weight, finish, and overall look of each smoke detector after installing units on a white ceiling.

Special safety features: I tested and evaluated each smoke detectors’ extra safety features, such as voice or light notifications, removal prevention, and more. For example, even though all the models I tested featured some kind of visual alarm component, the ultra-bright LED of the X-Sense SD01 was much more effective compared to the rest, and could be beneficial to those with hearing issues. Or the straightforward voice commands of the Nest Protect might be preferred by those who might get confused or disoriented by the single alarm siren of the other models.  

Operation: Throughout my testing, I made sure to use and observe each mode the smoke detectors offered. This included their testing and silence buttons, how they utilized any LED lights, and whether or not they included carbon monoxide detection.

Maintenance: I took note of the approximate lifespan of each unit, and the specifics of its battery replacement procedures. 

Types of smoke detectors

Battery: Smoke detectors can either be hardwired or standalone battery-powered units. Battery-powered detectors are easier to install than hard-wired units and are unaffected in the event of a power outage. Some newer smoke detectors are designed with lithium batteries inside the unit which can last up to 10 years without needing to be replaced. Units that use replaceable batteries typically need new batteries every six months and are vulnerable to tampering and being disconnected during false alarms caused by non-emergency situations like cooking smoke or steamy showers.

Hard-Wired: Hard-wired smoke detectors connect directly to your home’s electrical wiring, and typically have a backup battery in case of a power outage. These will initially need some electrical know-how or the help of a professional to be installed, but once the system is set up, it’s pretty easy to disconnect and install new units whenever you need them. Yahoodain recommends hard-wired smoke detectors since they’re easy to interconnect, so if one goes off, they all go off. 

Photoelectric: Smoke detectors use either photoelectric or ionization sensors to detect smoke. Some, like the First Alert SA320 that we tested, use both. Photoelectric smoke alarms use an LED light to detect smoke and are more responsive to slow-burning, smoldering fires than ionization alarms. When smoke particles enter the unit, they disrupt the light beam, which reflects it into a sensor and activates the alarm. These types of sensors are generally superior to ionization sensors because smoldering fires tend to be more dangerous and can go unnoticed for longer periods of time than flash fires, or ones that develop very suddenly and intensely. They also cut down on unnecessary nuisance alarms like which can cause people to remove the batteries out of frustration.

Ionization Sensors: These sensors are typically more effective at detecting flash fires. They do this by utilizing a small amount of radioactive material and placing it between two electrically charged plates. When smoke displaces the radioactive ions, the current between the plates is disrupted, and the alarm goes off. Ionization sensors have a higher chance of detecting nuisance alarms and tend to be much less effective at detecting smoldering fires. 

FAQs

Where should I install my smoke detector?

Even the best smoke detectors are only effective if they’re installed correctly. The NFPA recommends installing alarms inside and outside of every bedroom, and on every level of your home, including the basement. It also recommends installing both photoelectric and ionization smoke alarms or a dual-sensor detector as they can provide more protection than just one type of sensor.

Andler said that smoke alarms should be placed on your ceiling, not on the wall. Since smoke rises and begins gathering at the ceiling first, they have a much better chance of detecting smoke than a wall-mounted detector. As we mentioned earlier, seconds count when it comes to escaping a house fire, so correct placement is extremely important.

Andler also stressed the importance of having additional smoke detectors. He said that in the event of a fire in your home, hallway smoke detectors can sound their alarms much earlier than a bedroom alarm. Seconds count in home fires, and the early warning from hallway alarms can provide the extra time you and your family need to escape safely. 

He also recommends having a smoke alarm near — but not inside — the kitchen, to reduce the chances of false alarms. The Arizona Burn Foundation recommends keeping your detector at least 10 feet away from the stove. 

How do I test my smoke detector so I know it’s working?

Your smoke detector should have a “test” button. Press and hold it for a few seconds, and a high-pitched siren should start to sound. If there’s no sound or the sound is non-existent, it’s time to replace the battery. Many insurance companies also advise replacing the batteries every six months regardless of the siren loudness. 

What certifications should I look for in a smoke detector?

Whichever smoke detector you choose, make sure it meets the standards of Underwriter Laboratories (UL). UL is a third-party certification company that has been developing smoke detector standards for more than 40 years, and with their stamp of approval, you can trust that your unit will do its job.

The UL 217 code covers both “single station” smoke alarms that function as standalone units,  and “multiple station” smoke alarms that are interconnected — so when one goes off, they all go off. All the products we tested have this UL 217 certification, and our two combination smoke/carbon monoxide detectors, Nest Protect and First Alert SA320, also have a UL 2034 certification, which covers the CO detector.

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