Is it safe to rely on just one carbon monoxide alarm (hallway vs bedrooms)?

Short answer

Why people ask this

People often start with a single alarm in a central spot and assume it covers the whole home. The question usually comes up when bedrooms are down a hallway, doors are closed at night, and the home has fuel-burning appliances like gas heat or an attached garage.

When it might be safe

• A working alarm placed according to its instructions, with regularly tested batteries
• A small home layout where bedrooms are near the existing alarm and doors aren’t tightly sealed
• You also reduce sources (no idling vehicles in garage, appliances properly vented, fireplaces used correctly)

When it is not safe

• Relying on one alarm when bedrooms are far away or doors are closed overnight
• Using an old alarm past its replacement date or one that’s frequently disabled due to nuisance alerts
• Assuming a smoke alarm covers CO (they’re different unless labeled as a combo unit)

Possible risks

• CO can accumulate differently across rooms depending on airflow and door position
• Sleeping reduces your ability to notice early symptoms, so bedroom coverage matters
• Power outages can disable plug-in alarms without battery backup
• False confidence can lead to riskier behavior (like warming a garage or blocking vents)

Safer alternatives

• Add a CO alarm near sleeping areas (or in bedrooms if recommended for your unit)
• Choose alarms with battery backup, especially if outages are common
• Test alarms regularly and replace them on schedule per the manufacturer guidance
• Have fuel-burning appliances and vents checked if you suspect recurring issues

Bottom line

One CO alarm is a good start, but coverage near sleeping areas is usually a safer setup. Add alarms where people sleep and make sure they work during outages.

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