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?

The minimum required by most building codes and fire safety organizations:

• 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: you need a minimum of three detectors — basement level, main level, and upper level hallway outside the bedrooms. Many fire safety authorities recommend placing one inside each individual bedroom as well.

Garage: If your home has an attached garage, place a detector in the adjacent living area. Vehicle exhaust from a running car in a closed garage is one of the most common sources of residential CO poisoning.

UK: British Standard BS EN 50291 applies. Most new homes and rentals (since 2022 regulations) require CO detectors in all rooms with fuel-burning appliances. For purchased homes, the same placement logic applies as above.

CA/AU/NZ: Requirements vary by province and state, but the international guidance is broadly consistent with US standards — every level, near sleeping areas, adjacent to fuel-burning appliances.

Where Not to Place CO Detectors

• Within 15 feet of fuel-burning appliances — the burst of CO during normal startup can trigger false alarms
• 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 — typically 5 to 7 years. The electrochemical sensors inside 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 their replacement date — or if you can't find a date — replace them. This is not optional.

If there are no CO detectors in the property at all, this is a safety deficiency to address before your first night.

Combination Smoke/CO Detectors vs. Dedicated Units

Combination units (smoke and CO in one device) are convenient and code-compliant in most jurisdictions. 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.

Dedicated CO detectors tend to last slightly longer and can be placed at the appropriate height (CO is approximately the same density as air; smoke detectors should go near the ceiling; most code-compliant combination units are placed at the ceiling and still perform adequately for CO).

For a practical approach: combination units at each bedroom hallway, dedicated smoke detectors inside bedrooms and in the kitchen.

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 on the back of each CO detector. Anything over 7 years old needs replacement. Anything over 10 years old definitely needs replacement.
5. Verify detector placement matches the requirements above — every floor, outside sleeping areas.
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.