How a Carbon Monoxide Detector Works (and Why You Can’t Do Without One)

Protect yourself against this common home hazard

Brianne Sandorf
Nov 15, 2022
Icon Time To Read3 min read

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Did you ever hear the classic Reddit tale of the paranoid guy who thought his landlord was breaking into his apartment to leave notes?

Turned out the poor fella just had a case of long-term carbon monoxide exposure. He was leaving himself notes. He just couldn't remember it because of the CO he'd been breathing.

He’s lucky that he came out of it with nothing worse than a creepy tale, because carbon monoxide is deadly. At, we recommend always having a working carbon monoxide detector in your home to protect you and yours. But … how do they even work?

Why do you need a carbon monoxide detector?

Let’s do a quick FAQ about why you need a carbon monoxide detector in your home.

Carbon monoxide is a colorless and odorless gas that also happens to be super deadly in large concentrations.

It’s not what humans breathe out—that’s carbon dioxide. (One extra atom of oxygen makes all the difference.) Carbon dioxide isn’t great for humans, either, but it doesn’t come out of major household systems and appliances the way carbon monoxide can.

Short version: So you don’t get carbon monoxide poisoning.

Long version: carbon monoxide is a by-product of the flames produced by many household appliances, like heaters, dryers, stoves, grills, and more.

These appliances are designed to not overrun your home with CO fumes, but now and again, something goes wrong. And because carbon monoxide is a silent killer, without an alarm, you might not know what’s happening until it’s too late.

Carbon monoxide poisoning is when you inhale too much carbon monoxide.

Symptoms can include:

  • Headaches
  • Weakness
  • Dizziness
  • Nausea/vomiting
  • Shortness of breath
  • Confusion
  • Blurred vision
  • Unconsciousness

Some folks who have carbon monoxide poisoning make a full recovery. But for some, there can be long-term effects, such as:

  • Miscarriages and stillbirths
  • Permanent brain damage
  • Heart damage
  • Death¹

How sick you get and whether you make a full recovery depends on a few factors, like how much CO you breathe and for how long.

If you believe you have carbon monoxide poisoning, seek fresh air, then get medical treatment.

How do you know you have carbon monoxide poisoning?
Heads Up

If you’re feeling unwell for no apparent reason, try opening a window or going outside. If you feel much better, you’ll know CO could be the reason for your illness, and you’ll need to vacate your home until the air inside is tested.

But the easiest, surefire way to know you’re suffering from CO poisoning? A working carbon monoxide detector. With an alarm to warn you before you start feeling too sick, you’re also less likely to suffer long-term effects.

How does a carbon monoxide detector work?

There are three kinds of carbon monoxide detectors: electrochemical, metal oxide semiconductor, and biomimetic.

An electrochemical carbon monoxide alarm uses electrolytes for its early warning system. When carbon monoxide touches the electrolyte, a chemical reaction sets off the alarm.

An alarm that uses a metal oxide semiconductor depends on electrical circuitry. The contact with carbon monoxide completes a circuit that sets off the alarm.

Finally, a biomimetic sensor uses gel that mimics the hemoglobin in your blood. If the gel absorbs too much CO, the alarm goes off. Cool, right? We think it sounds like something from a sci-fi novel, but it’s 100% real.²

Regardless of the tech used, all three types will sense a carbon monoxide leak long before you’re in danger.

Which carbon monoxide detector should I choose?

Any functional CO detector is a good CO detector. But if you suffer from analysis paralysis, here are a few we recommend.

Top carbon monoxide detectors
Power source
Smoke detection
Kidde KN-COPP-3$34.05Plug
Icon No  DarkNo
Kidde KN-COSM-BA$44.99Battery
Icon Yes  DarkYes
Nest Protect$119.00Battery
Icon Yes  DarkYes
Onelink Safe & Sound$277.99Battery or wired
Icon Yes  DarkYes
Kidde Battery-Operated KN-Copp-B-LPM$19.99Battery
Icon No  DarkNo

Data effective 10/12/2022. Offers subject to change.

Not every carbon monoxide detector includes a smoke alarm and vice versa. Make sure you know what your detector includes, just in case you need to install a separate one for smoke.

Also, think hard about what types of detectors you need and where. Because CO rises, most folks opt for hardwired or battery-dependent ceiling installs. But that doesn’t mean you can’t use a plug-in model; you’ll just want to think hard about when and where to place it.

How do you install a carbon monoxide detector?

That depends on the kind of detector you buy.

If you buy a portable, battery-based detector, you just need to pop in some batteries, set the detector in your room of choice, and then run any required tests.

If you buy a plug-in detector, you only have to plug it in, then test it.

But if you’re buying a detector that goes on the ceiling, it’s a little more complicated. We’re no electricians, so we can’t take you on a step-by-step (although your alarm instructions should be able to). But here’s a general idea of steps you’ll likely take.

  1. Select a location. The National Fire Protection Association recommends CO alarms in every bedroom but suggests you follow manufacturer instructions to determine exact placement.
  2. If installing a hardwired alarm, install a ceiling box to house the wires.
  3. Screw the mounting bracket into the ceiling.
  4. Wire the alarm or install fresh batteries.
  5. Attach the alarm to the mounting bracket.
  6. Run the tests as instructed by the manufacturer.

Not for the faint of heart, especially when it comes to wiring. If you don’t have much electrical experience and don’t feel comfortable attempting the wires, ask someone more knowledgeable to do it for you.


So what did we learn today about carbon monoxide and carbon monoxide detectors? Well …

  • Why do you need a carbon monoxide detector? To warn you about carbon monoxide poisoning.
  • How does a carbon monoxide detector work? There are various ways, but in the end, they all provide early warning about the dangers of carbon monoxide gas.
  • Which carbon monoxide detector should I choose? Whichever one best suits your needs.
  • How do you install a carbon monoxide detector? It varies, but keep in mind that a wired installation is not for everyone.

You’re pretty knowledgeable about CO detectors now. Here are some other alarms to learn about. best of logo

Learn about smoke detectors. best of logo

Learn about home security systems.


Brianne Sandorf
Written by
Brianne Sandorf
Brianne has a degree in English and creative writing from Westminster College and has spent 6+ years writing professional, research-based content. Before joining, she wrote safety and security content for Her pieces and quotes are published across the web, including on, Social Catfish, and Hobbies include wearing a seatbelt, wearing a life jacket, and keeping her arms and legs inside the ride at all times. Contact her at

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