Where should a CO alarm be installed?

Install CO alarms on every level of the home, including inside or directly outside each sleeping area. The NFPA 720 and most local codes require CO alarms within 10 feet of each sleeping room. Avoid installation near stoves, fireplaces, or vents where false alarms may occur due to normal combustion drafts.

What CO level triggers an alarm?

UL 2034 requires CO alarms to sound within specific time windows: alarm within 35 minutes at 150 ppm CO, within 15 minutes at 200 ppm CO, and within 4–15 minutes at 400 ppm CO. The alarm will NOT sound at concentrations below 70 ppm for more than 60 minutes — low-level chronic exposure monitoring requires industrial CO detectors.

How long does a CO alarm last before replacement?

Most residential CO alarms have a rated service life of 5–7 years. The electrochemical CO sensor degrades over time and must be replaced at end of life. The alarm's end-of-life warning (a distinct chirp pattern) indicates the unit must be replaced, not just the battery. Check the date of manufacture on the back of the unit.

What should I do when my CO alarm sounds?

Immediately evacuate all occupants from the building. Do not re-enter. Call 911 or your local fire department from outside. Do not assume the alarm is a false alarm. CO is odorless and colorless — the alarm may be the only warning. Seek medical attention if anyone experiences headache, dizziness, nausea, or confusion.

Does this CO alarm require a battery or hardwire installation?

See the product specifications for power requirements. First Alert CO alarms are available in battery-operated (9V or AA), plug-in, plug-in with battery backup, and hardwire with battery backup configurations. Battery backup is important for hardwired models to ensure protection during power outages.

Can a CO alarm detect gas leaks (natural gas or propane)?

No. Carbon monoxide (CO) alarms detect CO specifically — they do not detect natural gas, propane, or other combustible gases. For gas leak detection, install a combustible gas detector (methane/propane detector). These are separate devices with different sensor technologies.

First Alert CO511 Wireless Interconnect Carbon Monoxide Alarm with Voice Alert

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First Alert CO511 Wireless Interconnect Carbon Monoxide Alarm with Voice Alert

Name: First Alert CO511 Wireless Interconnect Carbon Monoxide Alarm with Voice Alert
Brand: First Alert

First Alert Carbon Monoxide Alarm

The First Alert CO511 Wireless Interconnect Carbon Monoxide Alarm takes CO safety to the next level - when one alarm sounds, all compatible First Alert wireless alarms sound together throughout your home, so you're al...

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battery carbon monoxide alarm CO detector CO511 First Alert voice alert wireless interconnect

The First Alert CO511 Wireless Interconnect Carbon Monoxide Alarm takes CO safety to the next level - when one alarm sounds, all compatible First Alert wireless alarms sound together throughout your home, so you're alerted no matter where you are.

Wirelessly interconnects with other compatible First Alert smoke and CO alarms
Voice alert announces the type of threat and its location
Powered by 2 AA batteries with low-battery warning
Loud 85dB alarm for immediate household-wide alert
7-year limited warranty
Dimensions: 5.13" x 5.13" x 2.38"

Ideal for multi-story homes and larger spaces. No wiring required - wireless interconnect works out of the box. Meets UL 2034 safety standards.

What to check before you buy

UL 2034 listing: Residential CO alarms in the US are listed to UL 2034. Industrial CO monitoring is a different class of instrument with different alarm thresholds.
Alarms expire: CO sensors have a finite life - commonly 7 to 10 years from manufacture. Many units now sound an end-of-life chirp and cannot be reset.
Placement: CO mixes with air rather than layering at the ceiling like smoke, so alarms go on every level and outside sleeping areas. Keep them away from fuel-burning appliances and vents to reduce nuisance alarms.
Digital display: A display showing parts per million lets you distinguish a low-level chronic leak from a spike, which matters when talking to responders.

How it compares to other carbon monoxide alarms we review

Product	List price
First Alert CO511 Wireless Interconnect Carbon Monoxide Alarm with Voice Alert (this page)	see listing
Kidde COB Battery-Powered Carbon Monoxide Alarm	$26.97
Kidde COP Plug-In Carbon Monoxide Alarm with Battery Backup	$34.97
Kidde COBD Carbon Monoxide Alarm, Portable AA with Digital Display	$31.97
Kidde COPD plug-in carbon monoxide alarm	$43.97
Kidde COB10 Carbon Monoxide Alarm, 10-Year Battery, LED Alarm-Only	$45.97
Kidde COBD10 Carbon Monoxide Alarm, 10-Year Battery with Digital Display	$52.97

List prices recorded when this page was last updated; Amazon pricing moves frequently, so check the live listing. Browse the full carbon monoxide alarms range.

Frequently asked questions

Where should CO alarms be installed?

On every level of the home and outside each sleeping area. Because CO mixes fairly evenly with air, height placement is less critical than it is for smoke alarms - follow the manufacturer instructions.

How long does a CO alarm last?

The electrochemical sensor has a limited life, commonly 7 to 10 years from the date of manufacture. Most modern units chirp at end of life and must be replaced, not reset.

What CO level is dangerous?

UL 2034 alarms are designed to respond to rising concentration over time, sounding faster at higher levels. Any alarm should be treated as real: get everyone outside and call emergency services.

Is a CO alarm the same as a smoke alarm?

No. They detect entirely different hazards. Combination units exist, but a smoke alarm alone offers no protection against carbon monoxide.

Why does my CO alarm chirp?

A single periodic chirp is usually low battery or end of sensor life; a repeating alarm pattern is a CO event. Check the manual for the specific pattern before assuming it is a battery.

Where do the specifications on this page come from?

They are taken from the manufacturer's published listing. WC Safety does not laboratory-test products, and nothing is claimed here that the manufacturer does not state.

Does WC Safety sell this product?

No. WC Safety is an independent review site and an Amazon Associate. Purchases happen on Amazon, and we earn a commission on qualifying purchases at no extra cost to you.

Brand / Vendor

First Alert

Model / SKU

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Product Type

Carbon Monoxide Alarm

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