Kidde Nighthawk AC Plug-in Operated Carbon Monoxide Alarm with Digital Display KN-COPP-3

Last updated date: April 15, 2019

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We looked at the top 1 Carbon Monoxide Detectors and dug through the reviews from 7 of the most popular review sites including Tuck, The Spruce, SafeWise, Review Lab, Best Consumer Reviews, Safety, A Secure Life and more. Through this analysis, we've determined the best Carbon Monoxide Detector you should buy.

Overall Take

The Kidde Nighthawk AC Plug-in Operated Carbon Monoxide Alarm with Digital Display KN-COPP-3 measures carbon monoxide levels as low as 11 ppm. The LCD will display current CO levels, helping you keep an eye on things long before there's a problem. The alarm is 85 decibels, ensuring you'll hear it even while sleeping. In our analysis of 60 expert reviews, the Kidde Kidde Nighthawk Carbon Monoxide Alarm placed 2nd 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
7 expert reviews
User Summarized Score
215 user reviews
Our Favorite Video Reviews
What experts liked
The Kidde Nighthawk’s digital display shows the current CO levels in the house, with sensitivity as low as 11 ppm.
- Tuck
Features on this Kidde include an LED display, a level button that lets users see the peak carbon-monoxide level detected since the last reset, a sensor-on indicator, and a test/reset button.
- The Spruce
March 1, 2019 | Full review
Some alarms only tell you if your carbon monoxide levels have reached critical mass. This one will tell you if any particles are in your home, so you’ll know if there’s a leak that’s getting worse and get to safety faster.
- SafeWise
Reviewers like the added security of knowing the exact levels of CO in their homes at all times; the Kidde KN-COPP-3 Nighthawk Plug-In Carbon Monoxide Alarm even displays CO levels that are below the threshold for alarm.
- Review Lab
The Kidde (KNCOPP3) Nighthawk Plug-In CO Alarm with Battery-Backup has a digital interface which displays the level of carbon monoxide the unit is sensing and the highest CO level the the alarm as recorded since last activation.
- Best Consumer Reviews
Digitally displays carbon monoxide levels to easily read level changes
- Safety
Kidde’s plug in alarm still includes a battery backup so it will work if the power goes out.
- A Secure Life
February 4, 2019 | Full review
What experts didn't like
Display accuracy is good, though not top-notch
- The Spruce
March 1, 2019 | Full review
This is only a carbon monoxide alarm. You’ll have to buy smoke alarms separately.
- SafeWise
Alarm cannot be snoozed. Unlike other carbon monoxide detectors, the Kidde KN-COPP-3 Nighthawk Plug-In Carbon Monoxide Alarm does not allow users to snooze false alarms. The device needs to be manually reset each time.
- Review Lab
The main downside of a plug-in alarm is that it is within reach of small kids. If you’re worried about kids tampering with the detector, you’re probably better off with one that can be mounted high up.
- A Secure Life
February 4, 2019 | Full review

From The Manufacturer

Digital Display – Displays the level of carbon monoxide the unit is sensing. The unit updates this reading every 15 seconds.Protect your family from the dangers of carbon monoxide (CO) exposure with the Kidde KN-COPP-3 Nighthawk Plug-In Carbon Monoxide Alarm with Battery Backup and Digital Display. The Nighthawk is an easy-to-install unit that provides reliable protection against the dangers of CO. It features a digital display that shows CO levels in parts per million allowing you to see if, how, and when levels change.

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.