Missing Carbon Monoxide Alarms: What It Means on Your Home Inspection Report

Your inspector found no carbon monoxide (CO) alarms in the house, or found some but not on every level or outside the bedrooms. Under the InterNACHI Standards of Practice, one of the standards home inspectors work under, the inspector checks for the presence of smoke and CO detectors and reports their absence as needing correction. The same standards call out a missing CO detector in a room with a fireplace. Inspectors aren't required to test the alarms, so "present" on a report doesn't mean "working."

It's also a finding you can usually fix yourself: battery-operated and plug-in alarms need no wiring, so there's no reason to spend a night in the house without them.

Why It Matters

The CPSC calls carbon monoxide "a deadly, colorless, odorless, poisonous gas." The NFPA explains that it's created when fuels such as natural gas, propane, oil, wood, or gasoline burn incompletely, so a home's heating and cooking equipment can be a source, and so can a car or generator running in an attached garage. The CDC's carbon monoxide page, dated January 12, 2026, says more than 400 Americans die each year from unintentional CO poisoning not linked to fires, and that people who are asleep can die before they have symptoms. You can't see or smell it, so an alarm is your warning.

Where the safety agencies say CO alarms go:

• Every level of the home and outside sleeping areas. That's the CPSC's advice. The NFPA says a central location outside each sleeping area, on every level, and anywhere else applicable laws, codes, or standards require.
• Interconnected if possible. "Interconnected CO alarms are best; when one sounds, they all sound," the CPSC says.
• With battery power. Use battery-operated alarms, or plug-in or hardwired alarms with battery backup (CPSC).
• Listed. The CPSC says to choose an alarm that meets the current UL 2034 standard; the NFPA says to look for the label of a recognized testing laboratory.
• Not in the wrong spot. The CPSC advises against kitchens and spots above fuel-burning appliances, and says to avoid heating vents and anywhere furniture or drapes can cover the alarm. Follow the maker's instructions for placement and mounting height (NFPA).

What makes it more urgent: fuel-burning appliances, a fireplace, or an attached garage; other findings on the same report that involve combustion, such as a cracked heat exchanger, flame rollout, or water heater backdrafting; and anyone in the house with headaches, dizziness, weakness, upset stomach, or confusion, symptoms the CDC lists. If a CO alarm ever sounds, the CPSC says to move outside to fresh air right away, call 911, and not go back in until responders say it's safe (see CO alarm going off).

No gas appliances? Payne's furnace manual still says to install a CO alarm "even if you do not own a gas appliance," and the CPSC's every-level advice doesn't carve out all-electric homes.

What to Do Before Closing

• Ask the inspector which levels and areas were missing alarms, and whether the existing ones looked old. The CPSC notes that alarms have a recommended replacement age, found in the product literature or from the maker.
• Ask what your state or city requires. The NFPA's placement advice adds "other locations where required by applicable laws, codes or standards," and those rules vary. Your agent or the local fire or building department can tell you what applies.
• Talk to your real estate agent about whether to ask the seller to install alarms. Since you can put up battery or plug-in alarms yourself, you may decide to handle it right after closing.

What to Do After You Move In

1. Install alarms on every level and outside each sleeping area before the first night, following the maker's instructions. Our smoke and CO alarm guide compares sealed 10-year, plug-in, hardwired, and combination units.
2. Test them monthly. The CPSC and NFPA both say once a month; our alarm testing guide shows how. The CPSC notes that the test button checks the circuitry, not the sensor's accuracy, so replace each alarm by the date its maker gives.
3. Have fuel-burning appliances serviced yearly. The CPSC says a CO alarm "is no substitute for proper use and upkeep of appliances that can produce CO," and recommends having the heating system, including chimneys and flues, inspected and serviced every year.

Can You Fix It Yourself?

Yes, for battery-operated and plug-in alarms: mount or plug them in where the maker's instructions say, and test them. Adding new hardwired, interconnected alarms means new wiring, which is a licensed electrician's job; if the house already has hardwired alarms, our alarm guide explains replacing them like for like.

Frequently Asked Questions

Do I need a CO alarm if my house is all-electric?

The CPSC's advice is every level and outside sleeping areas, with no exception for all-electric homes, and Payne's manual says to install one even if you don't own a gas appliance. The NFPA notes that vehicles or generators running in an attached garage can produce dangerous levels of CO, and that wood, like other fuels, makes it when it burns incompletely.

Is a missing CO alarm a code violation?

It depends on where you live. State and local rules vary, and the NFPA's guidance includes "other locations where required by applicable laws, codes or standards." Your local building or fire department can tell you what your home needs.

Does a smoke alarm detect carbon monoxide?

Only if it's a combination smoke and CO alarm, which the CPSC notes are available. Check the label or model before you count an existing alarm as CO coverage. Smoke alarms are their own finding; see missing smoke alarms.

The Bottom Line

Carbon monoxide gives no warning you can see or smell, and an alarm is how you find out. Put CO alarms on every level and outside each sleeping area, as the CPSC and NFPA advise, before your first night in the house, test them monthly, and have your fuel-burning appliances serviced every year. See more findings in our inspection report decoder.

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