Carbon monoxide (CO) is an odorless, colorless gas that can be deadly if it accumulates in enclosed spaces. Protecting your home and family from this silent threat requires a reliable carbon monoxide detector. There are many options on the market with different features to keep your household safe. In this article, we’ll explore the options and give guidance on choosing the best one for your home. Richard Trethewey, This Old House’s plumbing and heating expert, discusses carbon monoxide detectors in the video above.
Types of Carbon Monoxide Detectors
In this section, we’ll break down the main types of carbon monoxide detectors that homeowners typically purchase.
Plug-In Detectors
Plug-in carbon monoxide detectors are among the simplest and most affordable options available. These devices plug directly into an electrical outlet and provide continuous protection—as long as they’re connected to power. Here are some key features of plug-in detectors:
- Easy installation with no wiring required
- Often include a battery backup for protection during power outages
- Typically lower cost than other types
Some models feature a digital display showing current CO levels. These detectors should be placed strategically across the home for optimal coverage.
Pro Tip: Richard Trethewey, This Old House plumbing and heating expert, points out a critical reason why battery backup matters on plug-in models: “As soon as the power goes out, what do people do? They’re going to light a fireplace.” Or worse—fire up a generator, kerosene heater, or other fuel-burning device indoors. That’s exactly when CO risk spikes, and exactly when a plug-only detector would go dark without backup power.
Pro Tip: Look for models with an LCD display that shows both current and peak CO readings. According to This Old House Magazine, an LCD display “shows short-term peaks in CO levels—any reading above 30 ppm merits investigation—before it reaches alarm-tripping concentrations.” Units that log peak levels can also help emergency personnel determine the right treatment if a poisoning has occurred. And always verify the device carries a UL or ETL label confirming it meets current safety standards (UL 2034)—don’t purchase any CO device without one.
Unlike smoke detectors, which need to be mounted high on a ceiling, plug-in CO detectors work well at outlet height. As This Old House Magazine has noted, “Because carbon monoxide doesn’t rise like smoke, CO detectors don’t need to sit high on the wall. Instead, you can plug one into a socket” at a standard outlet location. Place them outside bedrooms and near gas- or oil-burning equipment and appliances, which can emit CO gas if they malfunction or are not properly installed.
Battery-Powered Detectors
Battery-powered carbon monoxide detectors can be mounted on walls or placed on shelves and operate even during power outages. These are some of the benefits of battery-powered detectors:
- No need for nearby electrical outlets
- Portable and easy to relocate if needed
- Unaffected by power outages
If you choose this type of carbon monoxide detector, periodically check to see if it needs new batteries. Some models combine battery power with plug-in capability for added versatility.
Hardwired Detectors
Hardwired carbon monoxide detectors are permanently connected to your home’s electrical system. These detectors offer several advantages:
- Consistent power supply without relying on batteries
- Often include a battery backup for protection during power outages
- Often interconnected with other detectors for whole-house alert systems
Some hardwired detectors combine CO detection with smoke detection for comprehensive safety. While hardwired detectors typically require professional installation, they provide reliable, long-term protection for your home.
Carbon Monoxide Detector Features
Consider the following features when deciding which carbon monoxide detector is the best fit for your home.
Digital Display
Digital carbon monoxide detectors provide real-time information about CO levels in your home. These models continuously monitor and display current CO concentrations. Some models track long-term exposure. Digital screens are also easy to read.
Voice Alerts
Some advanced carbon monoxide detectors include voice alert systems. This feature can wake you if an emergency arises overnight and can give you instructions on what to do. Many of these systems also tell you exactly which type of danger you’re in (CO, smoke, etc.). Voice alerts are a good choice for households with children or elderly members.
Smart Home Integration
Modern carbon monoxide detectors often offer smart home capabilities, allowing for enhanced monitoring and control. Smart detectors may include the following features:
- Easy access to testing and silencing features through mobile apps
- Integration with other smart home devices for automated responses
- Remote monitoring of CO levels and detector status
- Smartphone notifications when CO is detected
Placement and Installation of Carbon Monoxide Detectors
Avoid installing detectors directly above or beside fuel-burning appliances, and mount detectors at least 15 feet away from cooking or heating appliances. Follow manufacturer instructions for specific height and placement recommendations
Install at least one detector on each level of your home. Place detectors near sleeping areas—ideally outside the bedrooms. In the video, Trethewey emphasizes the importance of having a detector outside sleeping areas to wake occupants if CO levels rise during the night.
For the most comprehensive coverage, we also recommend placing detectors in areas where combustion gases may occur, such as basements or garages. Avoid placing detectors in dead air spaces, such as corners, where air circulation is limited. Make sure each detector is easily accessible for maintenance and testing.
Maintenance and Testing of Carbon Monoxide Detectors
Follow these steps to keep your detectors in top condition:
- Test your detectors monthly using the test button.
- Replace batteries in battery-powered or battery-backup units as recommended by the manufacturer.
- Clean detectors regularly by gently vacuuming or dusting them.
- Replace entire units according to the manufacturer’s guidelines, typically every five to seven years.
- Keep detectors free from paint, stickers, or other coverings that may impair their function.
It’s good practice to keep a log of testing and battery replacement dates. Be mindful of the detector’s expiration date (usually indicated on the unit). Listen for any chirping sounds, which often indicate the need for maintenance.
Understanding CO Levels and Detector Responses
Carbon monoxide detectors are designed to alert you to dangerous levels of CO in your home. Understanding how these devices label and respond to different CO concentrations can help you react appropriately to alarms. Here’s how you can interpret different readings:
- Low levels (below 50 ppm): Most detectors won’t alert you at this level but may display readings on digital models. Prolonged exposure to low levels can still pose health risks.
- Moderate levels (50–100 ppm): Detectors may sound after one to two hours of sustained exposure. These levels can cause symptoms like headaches and dizziness.
- High levels (over 100 ppm): Alarms typically sound within 10–40 minutes of high-level exposure, depending on concentration. High levels are dangerous and require immediate action.
- Extreme levels (over 400 ppm): Extreme levels indicate immediate danger, and alarms should sound within a few minutes. These levels can be life-threatening and require urgent evacuation.
Pro Tip: Richard Trethewey, This Old House plumbing and heating expert, emphasizes the importance of understanding cumulative exposure: “As I understand it, that is the big deal about carbon monoxide, right? It’s not just the peak, it’s really the prolonged effects over time that’s dangerous.” This is why detectors are engineered to factor in both concentration levels and duration of exposure before triggering an alarm.
Health Effects of Prolonged Exposure
Even exposure to low levels of carbon monoxide can be harmful over time. Children, the elderly, and those with respiratory conditions are particularly at risk. These are a few symptoms of CO poisoning:
- Chest pain
- Confusion
- Dizziness
- Fatigue
- Headaches
- Nausea
In severe cases, CO poisoning can lead to unconsciousness or death. If you suspect CO poisoning, seek fresh air and medical attention immediately.
Pro Tip: Edward P. Krenzelok, director of the Pittsburgh Poison Center and president of the American Academy of Clinical Toxicology, notes that individual sensitivity to carbon monoxide varies widely: “Who knows what everybody’s individual threshold is? The one thing you can say is, you don’t need carbon monoxide in your body.”
Action Steps When Alarms Sound
When a carbon monoxide detector alarms, follow these steps:
- Immediately move to fresh air—outside or by an open door or window.
- Account for all household members.
- Call emergency services and report the alarm.
- Do not re-enter the premises until professionals deem it safe.
By understanding CO levels and appropriate responses, you can act swiftly and effectively to protect your family.
