Kidde Temper Resistant Carbon Monoxide Alarm, Ac Powered, Plug In with Battery Backup Kn Cob Lcb A Reviews

Kidde Temper Resistant Carbon Monoxide Alarm, Ac Powered, Plug In with Battery Backup Kn Cob Lcb A

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Kidde's "Model KN-COB-LCB-A" Plug-in Carbon Monoxide Alarm Bests First Alert's CO600

Feb 28, 2011 (Updated Mar 14, 2011)
Review by  
Rated a Very Helpful Review

Pros:"Battery-backup" feature makes for a much more trustworthy alarm than the competing First Alert CO600.

Cons:Functions "only" seven years (which, nonetheless, beats the competing First Alert model by two years).

The Bottom Line:

Battery-backup and "Tamper-Resist" features (plus superior design) make this Kidde model a better deal than the comparably priced First Alert CO600. Note well my discussion of the Tamper-Resist feature.

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 Kidde’s model KN-COB-LCB-A; however, I'll now and again compare it to First Alert's competing plug-in model (CO600), not only because they're so closely priced but also because I've been using both products in my home for several months.

Like the competing First Alert, this Kidde model implements electrochemical-sensing technology, which is said to be the most accurate approach available. It features not only "AC-plug-in" convenience but also (potentially life-saving) "battery-backup" and "Tamper-Resist" features, which—along with other enhancements discussed below—make it a respectable value, considering that I found mine at Walmart for $23.97. This was about a dollar less than the usual price of the First Alert CO600 at my local Ace Hardware store. And, considering that the CO600 lacks "battery-backup" capability, it won’t work if electrical power is disrupted, and thus might not comply with some state or community regulations. In fact, the US Consumer Product Safety Commission's Document #466 categorically states (in section 9):

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


The Kidde user manual (included) states that CO on one level of the home might not reach other levels; thus, they recommend that you provide complete coverage by placing a CO alarm on every level of the home, making sure you can hear an alarm from all sleeping areas. However, the manual separately states that “if you install only one CO alarm in your home, install it near bedrooms, not in the basement or furnace room.”
As I'd opted to install my other (First Alert CO600) CO alarm in the first-floor living room of my house, I installed this Kidde unit on the second level, in the hallway outside my bedroom.

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, the Kidde's user manual simply cautions you not to install this alarm “in dead air spaces, such as peaks of vaulted ceilings or gabled roofs, where CO might not reach the sensor in time to provide early warning.” Otherwise, height doesn’t appear to be a major installation factor. Along these lines, 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.)

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.]

The Kidde manual recommends not installing the alarm in locations (including garages, kitchens and furnace rooms) that “may expose the sensor to substances that could damage or contaminate it."

Additionally, “do not install near vents, flues, chimneys, or forced/unforced air ventilation openings.”

Likewise you shouldn’t install it “within 5 feet of heating or cooking appliances;” in fact, it’s recommended that you install it at least 15 feet away “to prevent nuisance alarms.”

Be sure to read all of the manual’s sections regarding inappropriate installation locations.

Hands-on installation of the KN-COB-LCB-A is rather quick and easy:

1. Choose a standard, unswitched 120-volt AC outlet;
2. Pull the yellow (thin, flexible-plastic) tab to activate the (emergency-power) battery-backup feature. Important note: If you haven’t disabled the unit’s “Tamper-Resist” feature (by sliding the rear switch from the default “on” to the optional “off” position, the unit’s alarm should sound loudly until you plug it into the electrical outlet.)
3. Plug the unit into the outlet.

Note that this product includes a conventional 9-volt battery conveniently preinstalled. You simply pull out the aforementioned throwaway tab to activate the battery.

In the dark of night this Kidde unit incidentally serves me as a sort of greenish nightlight (albeit not as effectively illuminative as the regular variety). At all hours, the satisfying brightness of the Kidde’s separate (green "operation" and red "alarm") lights arguably makes it more likable than some competing models (including the aforementioned First Alert unit, whose single, "dual-function" red LED is so deeply recessed that it isn't nearly as bright as either of this Kidde's separate LEDs).

Testing the alarm

Before testing, be aware that the CO alarm is (appropriately) very loud. And prolonged, close-range exposure to the alarm noise could damage your hearing. Hence the manual suggests placing your fingers over the sounder opening (i.e., the circular hole at the lower right of the front panel) while testing the alarm.
Test the unit by pressing and releasing its "Test/Reset" button (on the front panel). You will hear four brief beeps; a five-second pause; and then four more beeps (which is a sample of how the unit would sound in the event of actual detection of CO gas).

During this test, the red "Alarm" light (LED) will flash rapidly, just as it would during an actual CO event. The alarm will then return to its normal operational mode (monitoring for CO).

The Tamper-Resist feature (and its "disable" switch)

With such a "plug-in" type of CO alarm, an unsupervised child could easily remove the alarm from the electrical outlet; accordingly, this Kidde model (unlike the competing First Alert CO600) includes a "Tamper-Resist" function such that the alarm can emit a (very loud) constant tone if it's unplugged from the wall socket. The pertinent sliding switch comes factory-set to the "on" position, but you can reposition it and thus disable the Tamper-Resist feature before/after you initially install this product. On the rear of the unit there is a so-called “Tamper-Resist activation switch” (i.e., a tiny, T-shaped pushbutton) adjacent to the “Tamper-Resist disable switch” (i.e., the aforementioned sliding—and recessed—switch). To disable the Tamper-Resist feature, first hold down the T-shaped pushbutton; then (by inserting a screwdriver’s tip into the adjacent, recessed area) firmly press and slide the "on/off" switch to the opposite (left) side. [Don't worry; both the pushbutton and the sliding switch are pretty clearly labeled—with both English and Spanish explanatory text—on the back panel.]

Note: At least one user reviewer elsewhere reported that, to his surprise, a brief electrical power outage activated the Tamper-Resist feature such that the alarm suddenly began blaring. As merely unplugging it from the wall socket had no effect, he found it necessary either to press (or temporarily tape down) the T-shaped pushbutton (on the back of the unit) or to use a screwdriver to slide the adjacent Tamper-Resist switch to the “off” position.

Now, while I feel compelled to convey that reviewer's unusual story (which I've no particular reason to disbelieve), I myself did not encounter any such erratic behavior when I conducted the following simple test. First, I activated the Tamper-Resist function and plugged the unit into a typical portable "power strip" that I had plugged into a wall socket. Then I unplugged that power strip from the wall socket (effectively simulating a power outage). The result? Nothing inappropriate happened. The alarm emitted no noise; the green "operate" LED shortly ceased to glow steadily (though it did flash infrequently—which served as a visual signal that the unit was now operating via the backup battery); also, I found it possible to press the "test" button in that mode, upon which the usual pattern of four brief beeps issued twice from the alarm, after which the unit returned to normal operation via the backup battery.

Thus my unit—with its Tamper-Resist function activated—did operate normally via the backup battery, as the vast majority of these Kidde units surely do.

That said (because there are virtually never any—potentially "tampering"—children in this house), I normally keep my unit's Tamper-Resist switch set to the “off” (left) position; but, regardless of which mode that switch is set to, I've no expectation that my unit (or the majority of other Kidde units out there) will ever begin emitting such false alarms. 

That aforementioned other reviewer also reported that "dust, smoke, etc." could likewise trip the alarm into sounding; in that case he found it necessary to blow some compressed air (evidently through the front panel’s aperture and/or slots) to clean the unit. Then he plugged the unit back into the wall, pressed the front “reset” button, and all was well again.

Now, again, I won't say I disbelieve that unusual story; however, after at least five months of continuous operation, my unit's slots remain virtually dust-free. Hence I conclude that your average, reasonably clean home should be perfectly compatible with this CO alarm—most likely for its entire (seven-year) lifespan.


This Kidde model (like many electrical products) is officially listed by the widely known, USA-headquartered Underwriters Laboratories Inc. By contrast, the aforementioned competing First Alert model CO600 is not UL-listed but is UL-compliant. Therefore certain "conventional" consumers might appreciate that this Kidde product is indeed UL-listed.

That said, this distinction is likely moot and insignificant to the average consumer, given that the competing First Alert product not only complies with UL specification 2034 but is also listed with the London-headquartered Intertek Group PLC. [I've elsewhere read a reviewer's surmise that "First Alert" merely wanted to save some UL-listing-fee money.]

What levels of CO cause an alarm? 

As this Kidde alarm is compliant with Underwriters Laboratories' Standard UL2034, its documentation states its carbon monoxide response times ["ppm" means "parts per million"]: 

"At 70 ppm (of CO), unit must alarm between 60 and 240 minutes.
"At 150 ppm, unit must alarm between 10 and 50 minutes.

"At 400 ppm, unit must alarm between 4 and 15 minutes."
Moreover, the Kidde manual states, “this alarm has not been investigated for carbon monoxide detection below 70 ppm.”

To give you an idea of the significance of those “ppm” numbers, the competing First Alert model’s user manual 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 this more full-featured Kidde KN-COB-LCB-A over that of the competing, relatively spartan First Alert CO600.

Although either plug-in product features a large, straightforward "test/alarm" button on the front of a somewhat oblong housing; and although both models are similarly sized, the First Alert looks relatively "cheap" while this Kidde looks relatively deluxe. Not only is the smallish dark-gray text ("TEST / SILENCE") on the CO600's front button a bit less elegant than the corresponding text on this Kidde's face, but also the Kidde features two LEDs: a green "operating" light on the left, and a red "alarm" light on the right; furthermore, both of those LEDs are neatly mounted flush with the front surface of the Kidde's similarly off-white plastic housing. By contrast, the First Alert unit has only one (red) LED that is mounted about midway between the front and 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 front button's bottom edge) but also (more weakly) through all of the housing's adjacent apertures, including even the alarm sounder port. Hence if the room is otherwise fully dark, the resultant, diffusely reddish effect frankly looks altogether slightly slipshod vis-à-vis this handsome Kidde.

Dimensions and weight

This Kidde model KN-COB-LCB-A 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). Contrasted with the competing, comparably sized First Alert model CO600, this Kidde weighs more than twice as much: 10.1 ounces (288 grams). Such perceptibly greater heft suggests superior build, durability and quality. [None of this, however, guarantees any greater reliability.]

Which is the more reliable alarm: Kidde, or First Alert?

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 do 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 this Kidde and the 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 the 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 "Kidde"—not to mention the "First Alert"—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 First Alert's CO600 (likewise an "85-decibel" model). [Note: this Kidde alarm's pitch is marginally—and, I think, inconsequentially—higher than that of the 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?

"Kidde" states that the model KN-COB-LCB-A not only includes a five-year warranty but also will provide seven years of operation.] After that time, the unit will emit a telltale, end-of-life "beep" every thirty seconds to let you know it needs replacing. At that point you should indeed replace it immediately, for, according to the manual, “it will not detect CO in that condition.”

Thus it would seem this "longer-lived" Kidde model delivers more bang for your buck than does the competing, aforementioned First Alert model.

The user manual

The model KN-COB-LCB-A manual—sparsely illustrated with five smallish, black-and-white line drawings—consists of a cheap-but-sufficient, repeatedly folded sheet of paper measuring 5 & 5/8” by 3 & 3/8" (folded) or about 26" wide by 3 & 3/8" high (unfolded). Each side of this sheet comprises eight columns of text/illustrations. An analogous Spanish version of this manual is also enclosed. Though the sans serif font is annoyingly tiny (seniors might need to wield a magnifier), it's high-contrast and otherwise legible.

The instructions—divided into sections with boldfaced headings—are pretty easy to follow. A table of contents comprises the following main sections: "Information About Carbon Monoxide;" “Product Features and Specifications;” "Installation Locations;" "Installation Instructions;" "Alarm Characteristics;" "Operating Characteristics;" "Maintenance" and "Limited Warranty."

Miscellaneous information:
From the Kidde manual’s “Product Features and Specifications” section:

Temperature: Operating range:  40 to 100 degrees Fahrenheit

Audible alarm: 85+ dB at 10’
Sensor: Electromechanical

Power: 120 volts AC, 60 Hz, 60 mA max; 9 volt battery backup


Though I myself lack the means to generate hard, laboratory data, I‘ve no reason to doubt that this Kidde model KN-COB-LCB-A—which I installed last September—is functioning satisfactorily where it's plugged in (rather low upon the wall in the upstairs hallway by my bedroom).

And my ears—however unscientifically—estimate that this "85-decibel" KN-COB-LCB-A is about equally as loud as the comparably priced, "UL2034-compliant" (albeit not "UL-listed") First Alert CO600, which I’ve been concurrently using for several months (throughout most of this winter).

Since both competing “plug-in” models are so closely priced, it might be instructive if I summarize the relative advantages of this Kidde product over the First Alert:

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

(2) First Alert’s CO600 includes only the primary "AC-plug-in" feature, and not the auxiliary "battery-backup" feature, of this 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) This Kidde—unlike the relatively "no-frills" First Alert alternative—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 First Alert model's single ("dual-function") red LED is too deeply recessed and thus isn't as satisfyingly bright as either of this Kidde's separate (green "operation" and red "alarm") lights;

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

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

Considering all of the above, I think this relatively deluxe, made-in-China KN-COB-LCB-A amounts to a significantly better deal than the relatively austere, made-in-Mexico First Alert CO600.

Recommend this product? Yes

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