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First Alert CO615

Est. $30
June 2013
by ConsumerSearch
First Alert CO615

Best plug-in carbon monoxide detector

  • Plugs into any standard outlet
  • Can operate on battery backup
  • Extremely loud horn
  • Seven-year limited warranty
  • CO level is not continuously displayed
  • Flimsy battery cover

Bottom Line

The First Alert CO615 is an effective and easy-to-install plug-in carbon monoxide detector. It operates on electricity but will run on battery backup during a power outage. It receives a recommendation from one testing organization and earns high marks from individual owners, although many complain about its flimsy battery cover. Those who don't want to buy batteries should pass on this detector, as it won't operate without them.


Safe and effective. Professional testers praise the First Alert CO615, citing its ability to detect high and low carbon monoxide levels, and owners agree. Although this unit is a plug-in model, owners say they feel more secure knowing it will run on backup batteries in the event of a power failure. However, the unit is not designed to run on battery power for long. CO levels are displayed when the indicator button is pressed, disappointing some users who would prefer a continual readout.

Owners praise the detector's few false alarms, but add that nuisance alarms can be silenced with any household remote control. The unit also has an incredibly loud horn, set at 85 decibels within 10 feet, and is destined to wake up even the soundest sleeper. Some of the device's negative feedback stems from misunderstandings about the unit's battery backup; the unit will not operate without batteries in place. Furthermore, there is no bypass option for battery backup use, forcing owners to use the function whether they want to or not. When the batteries run low, the incessant chirping is unnerving, writes an Amazon user.

Ease Of Use

Installation is a breeze. Most owners say the First Alert CO615 is easy to install, test and use. Its manual has been improved over the years and is now easier to read. This detector comes with a 6-foot extension cord, enabling it to be wall-mounted. It should be placed at least 4 inches from the ceiling and in an area where it's not obstructed. One reviewer cautions that owners with inquisitive young children should consider installing the unit out of reach to avoid accidental setoffs.

While the digital display screen is easy to read, it does not continuously display CO levels. To retrieve this info, you must push the indicator button. One Amazon reviewer complains this triggers "a cryptic sequence that frankly looks like it's malfunctioning." However, owners do appreciate the ability to monitor a potentially dangerous situation by pressing the Peak CO memory button, which lets them check the highest CO level recorded. The detector will save these readings until the owner clears the memory.


Lasts no more than seven years. The biggest flaw of this First Alert model is its flimsy battery compartment door. Several owners complain that after installing the batteries, the door is difficult to close and must be taped shut. But, the installed AA batteries are not depleted as long as the unit has power. Of note, the detector doesn't operate as well with rechargeable batteries; because they have a lower voltage, the unit considers the batteries discharged before they actually are. The first set of AA batteries is included.

The CO615 is equipped with a seven-year limited warranty, but is designed to last between five and seven years. When its sensors have worn away, users will hear the "end of life" beep every minute until the detector is removed, says a company representative. The date stamped on the back of the device is the manufacture date and will give owners an idea of when the detector should be replaced.

Where To Buy
First Alert CO615 Dual Power Carbon Monoxide Plug-In Alarm with Battery Backup and Digital Display

 (786 reviews)
Buy new: $59.99 $30.49   95 Used & new from $27.96

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Our Sources

1. tested 10 carbon monoxide alarms in two categories: interconnected alarms and stand-alone alarms. The consumer magazine tested the alarms' response to high and low carbon monoxide levels, and how accurately the alarms digitally displayed or voiced the carbon monoxide level. The First Alert CO615 was among the stand-alone alarms tested.

Review: CO & Smoke Alarmsq, Editors of, February 2011

2. publishes the reviews of the five best products and services in each category, bestowing special honor to one. Kerri Ryan names the First Alert CO615 her favorite, giving it a perfect score and praising the unit's backup-battery feature. The review highlights a couple of features from previous models. The current edition does not come with a remote and cannot be hardwired.

Review: Best Carbon Monoxide Detector, Kerri Ryan, Aug. 22, 2011


Over 360 owners reviewed the First Alert CO615, with about 55 percent giving it 5 out of 5 stars. Complaints from owners who gave low ratings centered on the poorly designed battery cover, or those owners found operating the device confusing.

Review: First Alert CO615 Carbon Monoxide Plug-In Alarm with Battery Backup and Digital Display, Contributors to, As of May 2013


The First Alert CO615 is the only carbon monoxide detector reviewed on this opinion website. Almost 40 people reviewed the device, giving it an average score of 88 out of 100. Generally, owners complimented its effectiveness and ease of use.

Review: First Alert Carbon Monoxide Plug In Alarm with Battery Backup and Digital Display #CO615 Reviews, Contributors to, As of May 2013


Nearly 50 people reviewed the First Alert CO615 at Walmart's site, giving it a 4.4-star rating. Some of the negative feedback stemmed from misunderstandings about the device. One reviewer, a home inspector with advanced detection equipment, writes that his unit accurately displays the appropriate 40 parts per million CO level whenever he smokes a cigarette. Yet, he gave the unit 3 stars because it does not produce an audible alarm at that level. A few minutes of cigarette smoke is not prolonged CO exposure, so the alarm will not sound.

Review: First Alert Plug-In with Battery Backup Carbon Monoxide Detector with Digital Display, CO615, Contributors to, As of May 2013

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