Types Of CO Detectors
These carbon monoxide
detectors work independently. They can be battery operated or plug into an AC
socket (with a battery backup in the event of a power failure). They are the
easiest type to install, but don't have the ability to trigger other alarms in the
home if they detect CO.
This type of CO detector connects
to other alarms in your home to create a network. The connection can be hard
wired or wireless, and the alarms can either plug into an AC outlet (with battery
backup) or be completely battery operated. The advantage of an interconnected
network is that when any one alarm sounds, they all sound, giving you an early
warning of danger in a remote room, or one that's otherwise currently
You can also find CO detectors that
are part of a combination alarm that includes a smoke detector. There are
pluses and minuses to these types of alarms, but if you think one is right for
your situation, combination smoke and CO detectors are covered in detail in our smoke detector report.
Carbon monoxide detectors save lives
Carbon monoxide (CO) is a
potentially deadly, odorless and colorless gas that is estimated to kill
approximately 500 people a year and sicken many others. Often called the
"silent killer," CO is a by-product of incomplete combustion and
comes from malfunctioning appliances, such as gas or oil furnaces, wood burning
stoves, or gas clothes dryers. When these appliances are not adequately
ventilated, or if they malfunction, carbon monoxide can build up in the home to
lethal levels. The list of potential sources of carbon monoxide also includes a
wealth of items that shouldn't be used indoors under any circumstances,
including propane heaters, portable generators and charcoal grills.
Unfortunately, people don't always follow safety instructions and may use these
According to MedlinePlus,
a service of the National Institutes of Health, CO is the leading cause of
poisoning in the United States. As noted by the Centers for Disease Control and Prevention (CDC), everyone is at risk from CO poisoning, though
infants, the elderly and those with certain conditions, such as heart disease,
are most at risk. If you are exposed to CO gas, you may notice symptoms such as
headache, dizziness, weakness, upset stomach, vomiting, chest pain, and
confusion, the CDC notes. If you are asleep, especially if you're intoxicated, your
chances of dying from CO exposure are greatly increased. If you survive,
recovery can be slow, and there is a chance that permanent brain damage can
The good news is that CO
poisoning is highly preventable and the CDC's site has a long list of mostly
common-sense steps to take. Those include servicing gas, oil or coal-burning
appliances regularly, and not using items such as charcoal grills and camp
stoves that are intended for outdoor use indoors. At the top of the list,
however, is this advice:
battery-operated or battery back-up CO detector in your home and check or
replace the battery when you change the time on your clocks each spring and
All carbon monoxide
detectors have a finite lifespan with sensors that wear out within five to
seven years. However, the newest detectors come equipped with an end-of-life
timer. When the time is up, the devices essentially self-destruct -- beeping at
a regular interval until replaced. Don't just trust the timer, though. The National Fire Protection Association (NFPA) recommends that you "Test CO alarms
at least once a month; replace them according to the manufacturer's
Make sure your CO detector is UL certified
All of the CO alarms in
this report meet Underwriters Laboratory standards (UL2034) designed to alert
people well before CO exposure becomes life threatening, but also to prevent
nuisance alarms (caused by things such as typical air pollution or normal
short-term emissions from properly operating appliances) that can cause
homeowners to tune out CO alarms, greatly reducing a detector's effectiveness. They
don't respond at all to very low CO levels below 30 parts per million. Once CO
levels reach 30 ppm, they won't sound until after 8 hours of continuous exposure.
At 70 ppm, they won't sound for at least 60 minutes, but must sound after 4
hours. At 150 ppm, there's a 10 minute delay, but the alarm will sound before
50 minutes have passed. Finally, at 400 ppm, there's a brief 4 minute delay,
and the alarm must sound before 15 minutes.
However, not every CO
detector available at retail meets UL standards. Last year, Consumer Reports rated three models it bought from online retailers, including Amazon and Ebay,
as "Don't Buy." Those models were the NetBoat WB_H3110061, Foho
YJ-806 and GoChange 882. They lacked any evidence of UL certification, and when
tested by Consumer Reports, performed inadequately -- either failing to sound
at lower concentrations of CO, or responding too quickly at any level, making
it more likely that consumers would ignore warnings as nuisance alarms. The
retailers removed those models, and similar ones, from their websites once informed
of the issue, Consumer Reports said, though also adding that they may still be
available on other sites. Consumer Reports also recommends that you check your
existing alarms and if they lack either the UL symbol or a statement that they been
otherwise tested by another lab and meet UL2034 standards, they be replaced.
The bottom line, then, is
that if a CO alarm sounds, the situation merits concern and you should respond
immediately. The NFPA says to do the following: "Move to a fresh air
location outdoors or by an open window or door. Make sure everyone inside the
home is accounted for. Call for help from a fresh air location and stay there
until emergency personnel [arrive]."
The best carbon monoxide detectors
Among stand-alone CO alarms, we saw
the best feedback for the (Est. $35). It's the only stand-alone
CO alarm to earn a Recommended rating from Consumer Reports. It also draws
nearly 1,600 mostly positive reviews from users posting at Amazon. The CO615 is
AC powered, but no messy wiring job is required; instead, just plug it into a
convenient outlet. While you can simply use a low-mounted AC outlet, the AC
adapter is removable and is equipped with six-foot extension cord for placement
"flexibility." This allows those looking for the best protection to
place the detector higher on the wall (at least five feet above the floor) per
the recommendations of most experts. Two AA batteries provide backup for
continuous monitoring, even when AC power is out.
The CO615 isn't the most feature
packed CO detector, but there are a few nice touches. The LCD display won't
display continuous CO levels, but can show the peak CO levels over the last 24
hours at the touch of a button. The warning chirp if the back-up batteries
become low can be silenced for eight hours. Some sites continue to list the
existence of a feature that lets you silence the battery back-up warning with
any standard IR remote control, but that feature proved to be problematic and
has since been dropped.
Testing looks good for the CO615. It
earns the top rating at Consumer Reports for its ability to detect high and low
levels of CO. Like all CO alarms in this report, it meets UL2034 standards for
its ability to issue warnings that protect life without subjecting users to
User reviews are also highly positive.
We noted some gripes about build quality, particularly a battery door that's sometimes
called flimsy, and a few found the CO detector challenging to use, or claimed
that it arrived defective. However, those are well offset by a majority that
seem mostly-to-completely pleased with the CO alarm. It earns a 4.5-star rating
If you prefer Kidde products, the (Est. $30) is similarly priced, and
similarly well-liked by users. However, in expert testing, the CO615 is judged
to be a step better at detecting low levels of CO (though the Nighthawk is
still very good in that regard), and is said to have a
higher-quality/more-effective display. Still, users at Amazon rate the Kiddie an
identical 4.5 stars, and that's based on even more reviews -- over 2,550.
Like the First Alert, the KN-COPP-3 is
designed to be plugged into an existing outlet, but, again, is equipped with a
removable adapter for mounting higher on a wall or on a tabletop. Most users
are extremely pleased, though we did see some comments claiming that the unit
burns through back up batteries even when plugged in.
For those looking for a competent,
easy-to-install carbon monoxide detector at the lowest possible price, things
don't get much more basic than the (Est. $17). This CO alarm is battery powered, which gives you all the
installation flexibility you might need -- though again it might be wise to
heed expert advice to install it high above the floor. There's little in the
way of features -- no readouts or voice warnings here -- just a button to
silence nuisance alarms and a pair of LEDs to indicate that the unit is
operating or if an alarm is sounding.
User reviews are generally positive,
though complaints about defective units or excessive battery usage are not
unheard of. Still, Amazon users rate the carbon monoxide alarm a solid 4.6
stars based on more than 450 reviews. At Home Depot, where this model is sold
under the Code One brand, it earns an equally impressive score of 4.5 stars
after more than 500 reviews, with recommendations from 95 percent of users.
Interconnected alarms can provide an early warning
While users tend to prefer the
simplicity of stand-alone alarms, experts often prefer interconnected ones that
can alert homeowners to issues in areas that are currently unoccupied. Among
interconnected choices, we see good expert feedback for the (Est. $45). It's feature packed and easy to set up and use.
Many interconnected CO alarms require
a messy and expensive hard-wired installation, but the CO511B (sometimes also
sold as the First Alert CO511) uses a radio signal is used to communicate
between alarms. It's compatible with other First Alert wireless alarms,
including some models of smoke alarms and combination CO and smoke alarms; see
our report on smoke detectors for more information.
The feature list on the CO511B goes
well beyond its radio link, but that's a good place to start. The system
establishes a mesh network, independent of other networks, such as Wi-Fi within
your home. Each alarm acts both as a receiver and a transmitter, allowing the
network to extend further. Security codes and frequency hopping technology establish
stable and secure communications between alarms.
Other features include a voice alert
that includes location information so that you won't be left guessing which
alarm has sounded; up to 11 locations, such as a basement, can be programmed.
Latching technology provides a visual indication of which alarm sounded after
the alert has shut off. It also gives you a visual indication of which unit has
a low-battery condition. The alarm tone sweeps through low frequencies to aid
those with age-related or other hearing loss.
The First Alert CO511B does well in
expert testing by Consumer Reports, with top ratings across the board for
detecting high and low CO levels and for the quality of its voice alerts. User
reviews, while not plentiful, are generally positive. Most say that
installation is easy and that communication with other interconnectable First
Alert alarms -- smoke, CO or combination, and either battery operated or hard
wired -- works as advertised.
While the First Alert CO511B is a
great choice for homeowners looking to add CO protection with a minimum of muss
and fuss, if you are adding carbon monoxide alarms as part of new construction
or a major remodeling job, you, or your contractor, might prefer a hardwired
unit. The First Alert CO511B is completely battery powered and, while battery
life should be reasonable, the batteries will need to be replaced periodically.
A hard-wired CO alarm should have a
battery as well (though not all do) to provide constant monitoring even during
power outages; however, it's only a back-up, the main power will draw from your
home's AC wiring. Among hardwired interconnected CO detectors, we saw good
feedback for the (Est. $45). It's not been
professionally tested, but we found over 160 user reviews at Amazon, and the
majority of owners are pleased as it earns a 4.6 star rating. Reviews at other
sites are less plentiful, but equally positive; a 4.7 star rating at Home Depot
based on over 30 reviews, for example.
Like the First Alert CO511B, the Kidde
KN-COP-IC can be used in a network of compatible Kidde alarms, including smoke
and combination CO and smoke detectors, interconnected via a simple wired network.
Installation is reported as easy as long as walls are down (as part of a larger
remodeling project, for example) or a compatible Kidde alarm network is already
in place; otherwise you might want to enlist the aid of an electrician to run
the connections between units.
Installation considerations aside, The
KN-COP-IC looks to be a fine unit. It lacks some of the features found in the CO511B,
such as a voice alert, but adds others that the First Alert alarm lacks. Chief
among those is a readout that displays CO levels, updated every 15 seconds. It
also has a peak memory that can recall the highest CO level measured since the
alarm was last reset.
Expert & User Review Sources
While there are a number of sites that
report on CO detectors, the only one we spotted that does current, credible
testing is Consumer Reports. Editors there rate each detector on its
ability to respond to both high and low levels of CO, and the quality and
accuracy of the display or, if a feature of the tested alarm, voice message.
Beyond that, we looked to the feedback from owners posting at sites such as Amazon, Home Depot, Lowe's and elsewhere. That feedback is extremely
helpful in assessing things such as ease of installation and reliability --
including freedom from excessive false alarms.