First Alert's Model CO600 Plug-in Carbon Monoxide Alarm: How Does It Compare to Kidde's KN-COB-LCB-A?

Dec 1, 2010 (Updated Dec 6, 2010)
Review by  
Rated a Very Helpful Review

Pros:Its "batteryless" design makes for quick, easy and affordable installation. It's UL-compliant (albeit not UL-listed).

Cons:No "emergency-backup" battery. Competing model lasts longer. [See my final section for summary of "Cons."]

The Bottom Line: The CO600 is eminently easy to install and might suffice as a CO alarm (especially a "secondary" one). However, its lack of an emergency-backup battery makes it—potentially—dangerously untrustworthy.

Prefatory note: For a SUMMARY of my major points, feel free to skip ahead to the final section of this review.


Carbon Monoxide: The Insidious Killer

You can't see or smell carbon monoxide (CO), but it can kill you. Such home appliances as furnaces and some water heaters—if they become defective or are not properly ventilated—can release CO gas into the air you breathe. In smaller concentrations, CO can cause flu-like fatigue, headaches, or nausea. Larger concentrations can be lethal within two hours or less.

Fortunately, at the prorated cost of less than a penny per day, you can safeguard yourself and your loved ones with a CO alarm from such established, US-based companies as "First Alert" (BRK Brands) and Kidde (pronounced "kidda"). This review will focus on First Alert's above-pictured CO600 (made in Mexico); additionally, I'll compare and contrast that model with the competing (comparably priced) Kidde KN-COB-LCB-A (made in China).

Both of those models implement electrochemical-sensing technology, which is said to be the most accurate approach available. And both feature "AC-plug-in" convenience; however, the Kidde model adds (potentially life-saving) "battery-backup" and "tamper-resist" features—as well as other enhancements—that make it the better buy.  

The First Alert Model CO600 Plug-in Carbon Monoxide Alarm
The Model CO600 is First Alert's most basic plug-in carbon monoxide alarm inasmuch as it lacks any "battery-backup" capability. Hence the unit won't function if electrical power is disrupted; and thus it might not comply with some state or community regulations. In fact, the US Consumer Product Safety Commission's Document #466 states (in section 9):

"Hard wired or plug-in CO alarms should have battery backup."

Nevertheless, after having recently installed the comparably priced, competing Kidde Model KN-COB-LCB-A near one of my split-level house's second-floor bedrooms (where I sleep), I decided to make do with this simpler First Alert model on the first floor (near the open stairwell to the basement level where my natural-gas furnace and water heater are located). Given that my neighborhood virtually never experiences any electrical power outages [knock on wood!], I figure this "batteryless" unit should suffice as a secondary alarm should my "primary" Kidde unit ever malfunction. [Moreover, it's generally recommended that you install a carbon monoxide alarm on every level of your home. That said, the technician who annually inspects my furnace (just beyond a doorway to the "rough" half of the basement) cautioned me not install a CO alarm anywhere near that appliance, lest the alarm be "falsely" triggered by merely transient traces of CO caused by occasional, harmless instances of "backdrafting."]

The bottom line is: if a significant "CO event" were to befall, unless I were continuously preoccupied with operating a power tool, blasting heavy-metal music, or singing in the shower (none of which, fortunately, is likely), there's now a CO alarm within easy earshot of all locations within this house's halls and rooms—including the basement.

Note that First Alert also markets a slightly cheaper, strictly battery-powered model (the CO400) that lacks "plug-in" capability. Given that I'm using this CO600 as a "secondary" or "backup" unit to the aforementioned Kidde product, I figure that, in this instance, I might as well enjoy the convenience—and economy—of never having to buy and replace batteries. After all, factoring the cost (and hassle) of annual battery replacement, the approximately five-bucks-cheaper, "battery-only" CO400 wouldn't end up seeming more economical than this "AC-only" CO600.

That said, if you're contemplating using this model CO600 as your only or primary carbon monoxide alarm, I would strongly urge you to instead choose First Alert's approximately five-bucks-costlier plug-in model (the CO605) that does include a "battery-backup" feature. [Better still, save some money by opting for Kidde's more powerfully and appealingly designed model KN-COB-LCB-A, which, at my neighborhood Walmart store, regularly retails for slightly less than the price of this relatively limited and plain CO600.]


The included English/Spanish user manual states:

"This CO Alarm is specifically designed for residential use, and may not provide adequate protection in non-residential applications."

The manual also stipulates "a CO alarm should be centrally located outside each separate sleeping area in the immediate vicinity of the bedrooms" and that (in a multi-level home) an additional CO alarm should be installed on each level of the home. Accordingly, having already installed my Kidde CO alarm on the second floor of my house, I opted to install this First Alert alarm on the first floor. The manual also states that, for added protection, you could install yet another alarm nearer—but at least 20 feet away from—your furnace (or other fuel-burning heat source).

Note: another "user reviewer" opined that a plug-in CO alarm is generally mounted too low upon a wall for it to be optimally effective. However, not only do First Alert's and Kidde's user manuals make no mention of height being an installation factor, but also the US Consumer Product Safety Commission's Document #466 states (in section 9):
"CO alarms may be installed into a plug-in receptacle or high on the wall." (The boldfacing is mine.)

Moreover, CO reportedly mixes with air so thoroughly and quickly that (in the event of a health/life-threatening CO event) it would generally spread throughout the home.

Hence you don't necessarily have to install a home CO alarm as high within a room or hallway as you would a smoke alarm. [However, if you were instead installing a combination "smoke/CO" alarm, you'd obviously need to mount the unit at a height appropriate for smoke detection.]

That said, the CO600 user manual does caution you not to install this alarm in locations (including garages, kitchens and furnace rooms) that are "extremely" dusty, dirty, greasy, humid, cold, hot, windy or sunny--not to mention "in outlets covered by curtains or other obstruction." Likewise you shouldn’t install it “within 5 feet of any cooking appliance” or “closer than 15 feet from a furnace or other fuel-burning heat source, or fuel-burning appliances like a water heater.” [Note: Essentially all of these "location" guidelines likewise pertain to the competing Kidde model KN-COB-LCB-A.]

Hands-on installation of the CO600 is quick and easy:

1. Plug the unit into a standard, unswitched 120-volt AC outlet where its audible alarm can easily awake you nightly from sleep;
2. When you plug it in, make sure its "POWER/ALARM" (red-LED) light shines continuously;
3. Test the unit by pressing its "Test/Silence" button firmly till the alarm emits a single, brief beep, which will be followed by: four loud beeps; a pause; and then four more loud beeps (which is a sample of how the unit would sound in the event of actual detection of CO gas). [And note that the "test" procedure—as well as the pattern of beeping—is essentially identical with the competing Kidde model.]

During this test, the CO600's "POWER/ALARM" light will flash rapidly, just as it would during an actual CO event. [And note that the competing Kidde model's red "alarm" LED analogously flashes whenever its alarm is sounding.]

Also note that an unsupervised child could easily remove the CO600 from the electrical outlet, and—conceivably—you might never discover it till after a CO tragedy occurs. By contrast, the competing Kidde model incorporates a "tamper-resist" function (that's selected/disabled via a rear, recessed, sliding switch) such that it can emit a very loud, constant tone if it's unplugged.

"Underwriters Labs versus Intertek" 

Regarding the widely known, USA-headquartered Underwriters Laboratories Inc. (vis-à-vis the London-headquartered Intertek Group PLC), note that the "First Alert" company (BRK Brands) touts this model CO600 as being fully UL-compliant (the package states it "complies with UL 2034"); nevertheless, it is not officially UL-listed (albeit it is "Intertek-listed"). I've elsewhere read a reviewer's surmise that this is purely because "First Alert" greedily wanted to save some UL-listing-fee money. In any case, the competing Kidde model is UL-listed. Although I myself don't distrust the basic functionality and reliability of this First Alert product, certain "conventional" consumers might frown on its not being UL-listed.

What levels of CO cause an alarm?
The user manual of this UL-compliant (albeit not UL-listed) product states:

"Underwriters Laboratories Inc. Standard UL2034 requires residential CO Alarms to sound when exposed to levels of CO and exposure times as described below. CO levels are measured in parts per million (ppm) of CO over time (in minutes)....
"If the alarm is exposed to 400 ppm of CO, IT MUST ALARM BETWEEN 4 and 15 MINUTES.
"If the alarm is exposed to 150 ppm of CO, IT MUST ALARM BETWEEN 10 and 50 MINUTES.
"If the alarm is exposed to 70 ppm of CO, IT MUST ALARM BETWEEN 60 and 240 MINUTES."

[The competing Kidde model likewise complies with this UL standard.]
The CO600 manual also states:

"An exposure to 100 ppm of CO for 20 minutes may not affect average, healthy adults, but after 4 hours the same level may cause headaches."


"An exposure to 400 ppm of CO may cause headaches in average, healthy adults after 35 minutes, but can cause death after 2 hours."

Outward appearance

While I'll readily concede that a CO alarm should be viewed primarily as a functional rather than a particularly stylish household object, I must say that I favor the outward appearance of the more full-featured Kidde KN-COB-LCB-A over that of this relatively spartan First Alert CO600.

Although either of these competing plug-in products features a large, straightforward "test/alarm" button on the front of a somewhat oblong housing; and although both models are similarly sized, this First Alert looks relatively "cheap" while the Kidde looks relatively deluxe. Not only is the smallish dark-gray text ("TEST / SILENCE") on this CO600's front button a bit less elegant than the corresponding text on the competing Kidde's face, but also the latter features two LEDs: a green "operating" light on the left, and a red "alarm" light on the right; moreover, both of those LEDs are neatly mounted flush with the front surface of the Kidde's similarly off-white plastic housing. By contrast, this First Alert unit has only one (red) LED that is mounted about midway between the front and the back (within the interior) of the housing and is less brightly discernible—especially during daylight hours—as the red light emanates not only through its intended little central port (at the oval button's bottom edge) but also (more weakly) through all of the housing's adjacent apertures, including even the leftward port for the alarm's speaker. Hence if the room is otherwise fully dark, the resultant, diffusely reddish effect frankly looks altogether slightly slipshod.

In fact, in the dark of night my Kidde unit (in the central hallway outside my bedroom) incidentally serves me as a sort of greenish nightlight (albeit not as effectively illuminative as the regular variety). By contrast, this First Alert's feebler emanations amount to virtually no "nightlight" whatsoever.

Furthermore, the Kidde's tastefully sculpted and labeled housing almost looks like a veritable artist designed it. By contrast, this First Alert unit—despite its nicely unangular contours—looks like it was relatively hastily and perfunctorily designed such that it ended up seeming decently "contemporary" (and undeniably "functional") but hardly elegant.

That said, provided you're sure you don't want battery-backup capability, there's nothing downright objectionable about this alarm's design (though I still frown on its somewhat dim light). Although neither this First Alert model nor the Kidde looked like much within their respective packages at Ace Hardware and Walmart, once I alternately installed each on my home's wall, this CO600 paled beside the more classily configured Kidde.

Dimensions and weight

With its hard-plastic housing, this model CO600 weighs (per my hands-on inspection) only 3.9 ounces (112 grams) and measures about 4.75" wide by 3.25" high. Its depth is about 1.5 inches, not including the non-polarized, two-prong plug that connects this alarm to any standard 120-volt electrical outlet.

The competing Kidde model weighs more than twice as much: 10.1 ounces (288 grams) and measures about 4 & 7/8" wide by 3 & 6/8" high. Its depth is about 1 & 6/8 inches (not including its non-polarized, two-prong plug). Thus, although the (slightly taller) Kidde is rather similarly sized, its perceptibly greater heft suggests superior build, durability and quality. [None of this, however, guarantees greater reliability.]

Which is the more reliable model?

Notwithstanding differences in appearance, size and weight, the crucial question is: Which model is more effective at detecting—and audibly reporting—the insidious presence of invisible, odorless carbon monoxide gas in the home? Thankfully, because my furnace—according to a recent test by an experienced technician—isn't emitting any detectable amount of CO, I myself can't definitively answer that question.

Nevertheless, both of these products comply with Underwriters Laboratories' Standard UL2034 (see above). And just as I'd trust virtually any of the popular, leading-brand smoke alarms to be “approximately” (within an acceptable range of discrepancy) equally effective for alerting me to a fire, so also do I presume that both the Kidde and this First Alert product would function comparably effectively to alert me in the event of a CO calamity. [Even so, especially considering that my furnace and water heater are rather old, I feel a tad safer with not one but two different CO alarms concurrently installed in this house.]

How LOUD is its alarm?

This CO alarm's so-called "beeps" sound virtually identical to the loud, high-pitched tones of your average residential smoke detector. [And, unsurprisingly, many smoke detectors likewise bear the "First Alert"—not to mention the "Kidde"—logo. (Moreover, costlier "combination" models can alarm you to both smoke and CO.)]

I lack the means to scientifically verify this CO alarm's touted 85-decibel noise level; but it sounds about equally as (somewhat painfully) loud as my nearby, preexisting, run-of-the-mill smoke alarm. Moreover, its loudness sounds neither appreciably greater nor appreciably less than that of the Kidde KN-COB-LCB-A (likewise an "85-decibel" model). [Note: the Kidde alarm's pitch is marginally—and, I think, inconsequentially—higher than that of this CO600.] Either product should alert the average sleeper, provided the unit is installed within reasonable earshot per the user manual.

That said, I've elsewhere read that certain sleeping individuals (including children and the elderly) didn't readily respond to, or recognize, such alarms' shrill signals. Hence it might be prudent for you to gather all family members and demonstrate the "test" button of any such carbon monoxide (not to mention smoke) alarm till they're thoroughly familiar with the potentially life-saving significance of those portentous tones.

How many years should it remain functional?

The manufacturer warrants this First Alert alarm for five years and states you'll have to replace it five years after initial use. [By contrast, "Kidde" states that its competing model KN-COB-LCB-A not only includes a five-year warranty but also will provide seven years of operation.] According to its user manual, this First Alert unit will emit telltale, end-of-life "chirps" to let you know (five years hence) when it needs replacing [and the Kidde unit will activate its analogous "end-of-life-chirping" seven years after initial use].

Thus it would seem the "longer-lived" Kidde model delivers more bang for your buck—assuming it will actually live up to its manufacturer's claims. [Having only recently installed these respective products, all I can say is I'll be rooting for both of 'em (not to mention my venerable furnace and water heater) to "live long and protect."]

The user manual

The CO600 manual—sparsely illustrated with five smallish, black-and-white line drawings—consists of a single sheet of paper measuring 3.75" by 3.25" (folded) or 19.5" wide by 15" high (unfolded). One side of this sheet comprises six columns of English text, and the opposite side is in Spanish. Though the sans serif font is annoyingly tiny (seniors might need to wield a magnifier), it's high-contrast and otherwise legible.

The instructions—logically divided into sections with boldfaced headings—are easy to follow. A table of contents comprises the following main sections: "Introduction;" "Installation;" "If Your CO Alarm Sounds;" "Testing and Maintenance;" "What You Need to Know About CO;" "Regulatory Information for CO Alarms;" "General Limitations of CO Alarms;" and "Troubleshooting Guide."

On the whole, this CO600 manual is roughly equivalent to the similarly "cheap-but-sufficient," repeatedly folded sheet included with the competing Kidde model.


This "user reviewer"—who himself lacks the means to generate hard, laboratory data, and who incidentally read the synopsis of a 2002 scientific study that discovered "a high malfunction rate for residential CO detectors“—doesn't particularly doubt his recently purchased, "UL2034-compliant" First Alert CO600 is functioning satisfactorily where it's plugged in (rather low upon the wall of this house's first-floor living room). And my ears—however unscientifically—estimate that this CO600 is about equally as loud as the comparably priced, "UL2034-compliant" and "UL-listed" Kidde model KN-COB-LCB-A, which, I trust, is simultaneously safeguarding me from its upstairs perch (in the hallway by my bedroom).

However, in the event of a protracted AC-power failure, this utterly "batteryless" CO600 (unlike either the competing Kidde or First Alert's somewhat costlier model CO605) couldn't operate.

Moreover, this unit's internal, single (dual-function) "POWER/ALARM" (red-LED) light is, arguably, way too deeply recessed; indeed, it is only faintly illuminative (i.e., relatively dim by night, and somewhat overlookable by day). Thus I find that lone LED less satisfactory than the bright-green "OPERATING" and the (adjacent) bright-red "ALARM" lights that are mounted tastefully flush with the face of the competing Kidde model. Moreover, the overall styling of that Kidde product—especially when viewed up-close—is classier than that of this relatively cheap-looking First Alert model.

And so, the chief shortcomings of this First Alert C0600 (in comparison with Kidde's KN-COB-LCB-A) are as follows:

(1) the "seven-year" Kidde should continue functioning fully two years longer than this "five-year" First Alert model;

(2) the CO600 includes only the primary "AC-plug-in" feature, and not the auxiliary "battery-backup" feature, of the Kidde [which, to sweeten the deal, comes with a conventional 9-volt battery conveniently preinstalled (you simply pull out a throwaway tab to activate the battery)];

(3) The Kidde—unlike this relatively "no-frills" First Alert unit—incorporates a "tamper-resist" function (that you can disable or reselect via a prudently recessed, sliding rear switch) such that it would emit a loud, constant tone if it were unplugged by a child from the wall;

(4) the CO600's single ("dual-function") red LED is too deeply recessed and thus isn't as satisfyingly bright as either of the Kidde's separate (green "operation" and red "alarm") lights;

(5) installed in one's home, this CO600 looks relatively "cheap" vis-à-vis the classier Kidde;

(6) the CO600 normally costs $24.99 at my local Ace Hardware store [but I used a "five-dollars-off" coupon] while the Kidde regularly costs $23.97 at my local Walmart.

Considering all of the above, I think the relatively deluxe, made-in-China KN-COB-LCB-A amounts to a significantly better deal than this relatively austere, made-in-Mexico CO600. Even so, I'll hereby stamp my (qualified) recommendation upon this product inasmuch as it does appear to do everything it was designed to do.

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