What Carbon Monoxide Detectors Do for Home Safety

Carbon monoxide (CO) is an invisible, odorless gas that can be dangerous even at low levels over time. Because you can’t see or smell it, the only reliable way to know it’s present is to use a carbon monoxide alarm. This page explains what CO is, where it comes from, what a CO detector actually detects, and how to decide if your home should have CO alarms.

What Is Carbon Monoxide?

Carbon monoxide is produced when fuels don’t burn completely. It can build up indoors if exhaust can’t escape properly or if equipment is damaged, blocked, or used incorrectly. CO can spread through a home and reach sleeping areas, which is why alarms are so important.

Why CO is dangerous

CO can prevent your body from using oxygen effectively.
People may not realize they’re being exposed because early symptoms can feel like everyday illness or fatigue.
CO exposure can affect anyone, including pets, and it can be especially dangerous while sleeping.

What Does a Carbon Monoxide Detector Do?

A carbon monoxide alarm monitors the air for elevated CO levels. If the alarm senses a dangerous concentration based on its internal safety thresholds, it sounds an alert so you can take action quickly.

What you can expect from a CO alarm

Continuous monitoring: it checks air over time, not just a single moment.
Audible alarm: loud alert designed to be heard from nearby areas.
Status indicators: many alarms include lights or display indicators that show power, alarm, or fault status (varies by model).
Test/Silence button: used to confirm operation and silence certain alerts (follow your model’s instructions).

What a CO alarm does not do

It does not remove carbon monoxide from the air.
It does not replace proper ventilation or appliance maintenance.
It does not prevent CO from being produced; it provides warning when CO levels become dangerous.

Where Does Carbon Monoxide Come From?

CO can be produced by common household sources that burn fuel. Problems usually occur when exhaust is blocked, equipment is malfunctioning, or a device is used in a way it wasn’t intended.

Common CO sources in and around a home

Furnaces, boilers, and water heaters
Fireplaces and wood stoves
Gas stoves, ovens, and space heaters
Portable generators (especially when used in or near the home)
Grills or other outdoor cooking equipment used indoors
Car or truck exhaust from attached garages (even with the garage door open)

Does a Carbon Monoxide Detector Detect Natural Gas?

In most cases, no. A standard carbon monoxide alarm is designed to detect carbon monoxide gas, not natural gas (methane) or propane. Natural gas detectors use different sensor technology and are made specifically to detect fuel-gas leaks.

CO vs natural gas: quick difference

Carbon monoxide: a toxic gas produced by incomplete combustion (danger is poisoning).
Natural gas (methane) / propane: a fuel gas that can leak (danger is fire/explosion and oxygen displacement in some cases).

If you are concerned about both risks, look for the right alarm type for each hazard, or a combination solution only if it specifically lists the gases it detects.

Do I Need a Carbon Monoxide Detector in My Home?

Many homes benefit from CO alarms, especially if there is any chance CO could be produced or enter the home. Even all-electric homes may be exposed if they share walls with other units, have attached garages nearby, or have fireplaces or other combustion sources.

You should strongly consider CO alarms if you have

Any fuel-burning appliance (gas, oil, wood, or pellet)
An attached garage
A fireplace or wood stove
A multi-unit living situation (apartment, condo, townhouse) where a neighboring unit could be a source
Any regularly used backup heat source or generator (even if used outdoors)

Quick guidance on how many and where

Install CO alarms outside each sleeping area.
Install CO alarms on every level of the home, including basements.
CO alarms do not need to be near the floor; follow your model’s mounting instructions.

Signs of Carbon Monoxide Exposure

If you suspect CO exposure, treat it seriously. Symptoms can vary, and people may experience them differently.

Headache
Dizziness
Nausea or vomiting
Shortness of breath
Confusion or unusual tiredness

Important: If your CO alarm sounds or anyone feels symptoms, move to fresh air and get help immediately.

Basic CO Alarm Care and Maintenance

Test regularly: many households test monthly using the Test/Silence button.
Power check: replace batteries as needed and confirm the alarm is receiving power (varies by model).
Keep it clean: gently remove dust buildup according to the manufacturer instructions.
Replace on schedule: CO alarms have a limited service life; replace the unit when it reaches end-of-life.

FAQs

What does a carbon monoxide detector actually detect?

It detects elevated carbon monoxide levels in the air over time. If the level becomes dangerous based on the alarm’s safety thresholds, it sounds an audible alert.

Will a CO detector detect a natural gas leak?

Usually no. Standard CO alarms are designed to detect carbon monoxide, not natural gas (methane) or propane. For fuel-gas leaks, use a detector that specifically lists natural gas or propane detection.

Where does carbon monoxide come from in a home?

CO can come from fuel-burning appliances (furnace, water heater, fireplace), car exhaust from attached garages, or equipment like generators or grills used improperly. CO risks increase if exhaust is blocked or equipment malfunctions.

Do I need a CO detector if my home is all-electric?

Many people still choose CO alarms, especially in multi-unit buildings or if there’s an attached garage nearby. CO can enter from adjacent spaces even if you don’t have fuel-burning appliances in your unit.