Carbon Monoxide Detector for a New Home: What You Need to Know

Carbon monoxide is odorless, colorless, and kills without warning. It's produced by any fuel-burning appliance — gas furnaces, water heaters, stoves, fireplaces, generators, and vehicle exhaust. The moment you take possession of a new home, the CO detector situation is your responsibility. Don't assume the previous owners handled it correctly.

How Many CO Detectors Do You Need?

Placement and quantity depend on local code and manufacturer guidance. Common code examples include:

• One on every level of the home, including the basement
• One inside or immediately outside every sleeping area (bedroom or hallway adjacent to bedrooms)

For a two-story home with a basement and three bedrooms sharing a hallway, that common example would place detectors on the basement, main, and upper levels, with the upper-level unit outside the sleeping area. Local code may call for additional units, including inside bedrooms.

Garage: If your home has an attached garage, follow local code and manufacturer guidance about placing a detector in the adjacent living area. Vehicle exhaust from a running car in a closed garage is a serious CO hazard.

Outside the US: Requirements vary by country, province, territory, and state. Follow local code and manufacturer guidance, especially for placement near sleeping areas and fuel-burning appliances.

Where Not to Place CO Detectors

• In locations prohibited by local code or the manufacturer's instructions
• Near vents, windows, or ceiling fans — drafts affect sensor performance
• In high-humidity rooms like bathrooms
• Directly above or next to stoves

When to Replace CO Detectors

CO detectors have a limited lifespan. Follow the manufacturer's replacement interval because the sensors degrade over time. An old detector may look functional and produce no alerts while actually being incapable of detecting CO at dangerous concentrations.

The expiration date is usually printed on the back of the unit. When you move into a new home, pull every CO detector off the wall and check the date. If any are past the manufacturer's replacement date — or if you can't find a date — replace them.

If there are no CO detectors in the property at all, treat this as a safety issue to address before your first night where local code or manufacturer guidance calls for them.

Combination Smoke/CO Detectors vs. Dedicated Units

Combination units (smoke and CO in one device) are convenient, but code compliance depends on the jurisdiction and model. They reduce the number of devices you need to install, test, and maintain. The tradeoff is that if the unit fails, you lose both protections simultaneously.

Follow the product instructions for placement and replacement of dedicated CO detectors and combination units. CO is approximately the same density as air; smoke detectors should go near the ceiling.

For a practical approach, place units near sleeping areas and fuel-burning appliances as local code and manufacturer guidance direct.

What to Do When You Move In

The new homeowner CO/smoke audit should happen on day one, before you sleep in the property:

1. Locate every smoke and CO detector in the house.
2. Press the test button on each one. A functioning unit will sound the alarm.
3. Replace batteries in all of them regardless of whether they seem fine — you don't know how old the current batteries are.
4. Check the manufacturing date and manufacturer's replacement interval on the back of each CO detector.
5. Verify detector placement against local code and manufacturer guidance, especially near sleeping areas and fuel-burning appliances.
6. Add any missing detectors.

A basic CO detector costs $20–$50 at any hardware store. Interconnected detectors (when one sounds, all sound) provide better protection in larger homes and are required by code in some jurisdictions.

If the CO Alarm Goes Off

Don't assume it's a false alarm. The sequence:

1. Get everyone and all pets out of the building immediately.
2. Leave the door open as you exit.
3. Call 911 from outside the building.
4. Don't re-enter until first responders clear the building.

CO alarms chirp regularly as low-battery warnings — this is different from the continuous alarm indicating CO detection. Learn the difference from the manual.

The Moving Day Toolkit includes a first-30-days safety audit checklist covering smoke detectors, CO detectors, fire extinguishers, and emergency shutoff valve locations — everything you need to verify on day one of ownership.