Nest Protect Smoke and Carbon Monoxide Alarm

Last updated date: April 15, 2019

Review Melt Score
9.5

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We looked at the top 1 Carbon Monoxide Detectors and dug through the reviews from 9 of the most popular review sites including Tom's Guide, BestReviews, Trusted Reviews, Digital Trends, New York Times Wirecutter, Tuck, TechHive, CNET, Reviews and more. Through this analysis, we've determined the best Carbon Monoxide Detector you should buy.

Overall Take

The Nest Protect Smoke and Carbon Monoxide Alarm is a unique type of carbon monoxide detector, also providing smoke detection. This is a smart alarm, which means it hooks up to your home's Wi-Fi and lets you monitor your CO levels using an app. If you do have an evacuation, the Nest detector will light a path to help you get out even if it's late at night. In our analysis of 62 expert reviews, the Nest Nest Protect Smoke & Carbon Monoxide Alarm placed 1st when we looked at the top 10 products in the category. For the full ranking, see below.

Editor's Note April 19, 2019:
Checkout The Best Carbon Monoxide Detector for a detailed review of all the top carbon monoxide detectors.

Expert Summarized Score
9.2
9 expert reviews
User Summarized Score
9.3
7,185 user reviews
Our Favorite Video Reviews
What experts liked
The Nest Protect uses a split-spectrum sensor that Nest says is good at detecting both slow-smouldering fires as well as fast-burning ones.
- Tom's Guide
November 20, 2018 | Full review
Combination smoke alarm/CO detector
- BestReviews
With automated rules that can safely light a path out of your home and a choice of battery-powered or wired models available, the Nest Protect is a smart smoke alarm.
- Trusted Reviews
December 12, 2018 | Full review
It uses both photoelectric and ionization sensors to detect both smoldering and full-on burning fires
- Digital Trends
April 13, 2019 | Full review
Nest’s uses what they call a Split-Spectrum Sensor, which, while photoelectric, promises to detect fast-burning fires more quickly, more in line with the performance of ionization sensors.
- New York Times Wirecutter
November 15, 2018 | Full review
The app notifies you whenever the battery is low and self-checks the alarm regularly to ensure it’s still working properly.
- Tuck
When an alarm is tripped, Nest Protect gets to work alerting you not just via its alarm, but also via a color-coded LED on the top of the device (yellow for low levels of smoke or CO, red for a “get-out-now” level of danger).
- TechHive
November 13, 2017 | Full review
The Protect has built-in sensors to detect electrochemical CO, heat, humidity, occupancy and ambient light, as well as a microphone.
- CNET
July 27, 2015 | Full review
Uses a speaker and calm voice to tell you whether smoke or carbon monoxide was detected, the room it’s in, and its level of danger
- Reviews
What experts didn't like
At $100, the Nest Protect is one of the most expensive, but also one of the most comprehensive, of the smart smoke detectors we've tested
- Tom's Guide
November 20, 2018 | Full review
CO readings not given in PPM
- BestReviews
There’s no getting away from the fact that it’s expensive, however.
- Trusted Reviews
December 12, 2018 | Full review
I have to admit, I’m a little wary of entrusting something as important as a smoke alarm to a smart device.
- Digital Trends
April 13, 2019 | Full review
These alarms are expensive compared with a standard smoke and CO alarm.
- New York Times Wirecutter
November 15, 2018 | Full review
At over $100, this carbon monoxide detector isn’t cheap, but for those who want the security of monitoring their CO levels anywhere with their smartphone, the price may be worth it.
- Tuck
Nest Protect isn’t cheap, but even at $119 it’s not the most expensive smart smoke detector on the market.
- TechHive
November 13, 2017 | Full review
Nagating the Nest app is pretty straightforward, but it has some quirks. From the main screen you can initiate a safety check whenever you like to ensure that the alarms are working and, supposedly, review your history. But, although I've tested the Protect over several days, no history has ever populated in the app
- CNET
July 27, 2015 | Full review
Reported complications in troubleshooting problems, including Wi-Fi disconnection and locating certain types of routers
- Reviews

From The Manufacturer

It’s time to expect more from your smoke alarm. Nest Protect has been redesigned from the inside out. It has a Split-Spectrum Sensor, tests itself automatically and lasts up to a decade. It’s also the first home alarm you can hush from your phone without any extra hardware required. And it tells you what’s wrong and can even alert your phone. Nest products are made to work together. And they can even work with lights, locks and other products in your home. The Nest Protect can alert the Nest Thermostat when it detects carbon monoxide and the Thermostat can turn off the furnace to try and reduce the leak while you get to safety. Nest is focused on making simple, human, delightful things. That’s how we’re creating the thoughtful home: A home that takes care of the people inside it and the world around it.

Overall Product Rankings

1. Nest Protect Smoke and Carbon Monoxide Alarm
Overall Score: 9.5
Expert Reviews: 9
3. First Alert Carbon Monoxide Alarm
Overall Score: 9.3
Expert Reviews: 5
4. Alert Plus Carbon Monoxide Alarm Detector
Overall Score: 9.1
Expert Reviews: 2
7. First Alert Smoke Alarm
Overall Score: 8.5
Expert Reviews: 6
8. Sensorcon Carbon Monoxide Detector
Overall Score: 8.0
Expert Reviews: 6
9. Kidde Battery Operated Carbon Monoxide Alarm
Overall Score: 7.7
Expert Reviews: 5
10. Roost PP3 (9v) Specialty Battery
Overall Score: 7.1
Expert Reviews: 4

An Overview On Carbon Monoxide Detectors

It’s known as the silent killer. An odorless, colorless gas, carbon monoxide seeps into a home and gradually poisons its occupants, killing an estimated 400 people per year. Symptoms are commonly mistaken for the flu, leading sufferers to delay getting treatment until it’s too late.

The Centers for Disease Control says one of the best ways to prevent carbon monoxide poisoning is to install a detector in your home and update your batteries at least every six months. You’ll need to place it close to your master bedroom to ensure you hear any late-night alerts and replace the detector at least every five years.

But the first step in protecting your family against carbon monoxide is to choose a good detector. There are many on the market that will do the job, but some features are more important than others. You can find a detector that will display carbon monoxide levels at all times, giving you reassurance it’s actively monitoring the safety of the air you’re breathing.

If you don’t already have functioning smoke detectors in your home, you may want to consider a unit that will protect your home against fire as well as carbon monoxide. You may also want to consider purchasing a device that links up to smoke detectors so that all of your devices communicate with each other.

You’ll notice some carbon monoxide detectors are wired while others are battery-powered. If you choose a wired model, make sure it has a battery backup that kicks in if the power goes out. Whether it’s battery-powered or wired, though, you’ll need to change the batteries at regular intervals. Experts recommend updating the batteries in your smoke and carbon when you adjust your clocks for Daylight Savings Time to keep the task easy to remember. However, you can buy detectors that will alert you when the battery is low.

Review Melt Fun Fact

In addition to buying a carbon monoxide detector and maintaining it, there are a few other things you can do to keep your family safe. Oil, wood and gas furnaces are common sources of CO, as are gas stoves or dryers. If you use a gas or oil water heater, candle or a gas lantern, you may also be at risk. One important preventive measure you can take is to schedule regular inspections of any gas, oil or coal-burning appliance. You should also never use a generator or other CO-emitting appliance inside your home. If you have an attached garage, avoid running a vehicle inside it, even if you have the garage door open.

The Carbon Monoxide Detector Buying Guide

  • Before you buy a carbon monoxide detector, you’ll need to understand safe levels. These can vary from household to household, depending on the length of your exposure and the overall health of each person who lives there. Occupational Safety and Health Standards require workplaces to keep levels below 50 ppm, but many people won’t experience symptoms until at least 70 ppm. Heart patients may begin experiencing chest pains as levels rise within that range, though. Once carbon monoxide hits 70 ppm and keeps rising, occupants may notice an increase in headaches, fatigue and nausea. Levels between 150 and 200 ppm can cause unconsciousness and disorientation and eventually become fatal.
  • Accuracy should be a top priority when you’re comparing carbon monoxide detectors. One way to measure accuracy is to check a unit’s sensitivity. The Kidde Nighthawk Carbon Monoxide Detector can sense levels as low as 11 ppm but will only alert when the level gets dangerous. The First Alert Carbon Monoxide Alarm uses electrochemical sensors that can find both low and carbon monoxide levels.
  • Before you start shopping, determine exactly what type of danger detection you need. The Nest Protect Smoke & Carbon Monoxide Detector is a smoke and carbon monoxide detector in one. The unit combines both photoelectric and ionization sensors to monitor for fires. Those same sensors can also keep an eye out for signs of electrochemical carbon monoxide. Most other carbon monoxide detectors only handle CO detection, which means you’ll need separate smoke detectors. However, if you’re in the market for a new smoke detector as well, consider the First Alert Carbon Monoxide Alarm, which connects to other First Alert alarms to provide you with full-house protection.
  • With most CO detectors, you’ll only know once levels reach a certain threshold. However, both the Kidde Nighthawk Carbon Monoxide Alarm and the Alert Plus Carbon Monoxide Alarm show your current levels on an LCD display. The Alert Plus Carbon Monoxide Alarm Detector will begin issuing alerts within 60 to 90 minutes once you reach 50 ppm. If you hit 100 ppm, an alert will sound within 10 to 40 minutes, and 300 ppm sets off an alarm within three minutes.
  • If you do see an alert, it can help to know which part of your house the problem area is. The First Alert Carbon Monoxide Alarm lets you know where the threat is so that you can take action to fix it.
  • In addition to voice alerts to warn you of the danger, Nest Protect Smoke & Carbon Monoxide Detector has an LED that changes colors at varying levels. If you have low levels of smoke or carbon monoxide, you’ll get a yellow light while red light signals that you should exit the building immediately. The Alert Plus Carbon Monoxide Alarm also has a bright LED light.
  • When an alarm goes off, it’s important to have an alert at a volume audible to your entire household. The National Fire Protection Association recommends volume levels of at least 75 decibels. Both the Kidde Nighthawk Carbon Monoxide Alarm and First Alert Carbon Monoxide Alarm include alarms that are 85 decibels.
  • Another benefit of the Nest Protect Smoke & Carbon Monoxide Detector is that it connects to a smartphone app. This means you can log in and check your home’s levels even when you’re away.
  • One bonus feature on the Nest Protect Smoke & Carbon Monoxide Detector is that if you do need to exit, the alarm lights up the area to help you find your way out in the dark. It can also be linked up to the smart bulbs you have in your home to provide a visual alert when it’s time to evacuate.
  • You have two choices in how your carbon monoxide detector is powered. The Kidde Nighthawk Carbon Monoxide Alarm is a plug-in detector that runs off your home’s electricity. It also has a battery backup for those power outages. The First Alert Carbon Monoxide Alarm and Alert Plus Carbon Monoxide Alarm Detector are both battery-powered, so you’ll need to make sure you keep the batteries changed. The Nest Protect Smoke & Carbon Monoxide Detector is available in both wired and battery-powered versions.