LIFE · BMC FIELD MANUAL
The Carbon Monoxide Alarm Plan: Placement, Testing and Exit Rules
A carbon-monoxide alarm is not a small appliance you install and forget. It is one point in a system: source control, correct placement, monthly tests, known end-of-life dates and a household that leaves when it sounds.
The useful answer
- CPSC recommends CO alarms on every level of the home and outside sleeping areas; local codes and the exact alarm instructions may require more.
- Interconnected alarms are best because one detected hazard can alert the whole home, but every device and connection method must be compatible and installed as directed.
- Test alarms monthly, replace batteries on the schedule required by the device, and record each unit’s manufacture, installation and end-of-life information.
- Alarms do not make indoor generators, charcoal grills, running vehicles or a gas range used for heat safe. Control the source first.
- If an alarm sounds or CO poisoning is suspected, get everyone into fresh air and call 911; do not search the house for the cause before leaving.
Treat alarms as the last warning layer
Carbon monoxide is a colorless, odorless poisonous gas created by incomplete fuel burning. You cannot reliably see or smell it, and early symptoms can resemble illness. The CPSC lists headache, dizziness, weakness, nausea, vomiting, sleepiness and confusion among warning signs. Severe exposure can impair judgment and movement before a person recognizes the danger.
An alarm helps detect a dangerous condition; it does not prevent one. Annual inspection of heating systems, chimneys and vents by a trained technician, correct appliance use and outdoor generator placement are separate controls. A silent alarm yesterday does not prove a furnace, water heater, fireplace or attached garage is safe today.
Make one household owner responsible for the alarm inventory without making that person the only one who understands it. Every adult and capable child should recognize the sound, know the exit destination and understand that the response begins outside. The plan must still work at night, during a power outage and when the usual decision-maker is away.
Map levels and sleeping areas
Draw the home by level and mark every sleeping area, fuel-burning appliance, fireplace, attached garage and likely generator location. CPSC guidance recommends battery-operated CO alarms or alarms with battery backup on every level and outside sleeping areas. It says CO alarms are not needed in an attic or basement unless that space includes a sleeping area, while local requirements may be stricter.
Placement within a room, height, distance from appliances and environmental limits come from the exact alarm manual and applicable local code. Do not copy the location of a smoke alarm automatically or use a generic internet diagram as installation authority. Avoid areas the manufacturer excludes because of temperature, humidity, airflow, cooking vapors or obstruction.
Walk the home with bedroom doors closed and background equipment running. Ask whether every sleeper can hear the alarm. The CPSC says interconnected CO alarms are best because when one sounds, all sound. Verify whether a system is hardwired, wirelessly interconnected or part of a listed combination device, and use only compatible components.
Choose identifiable alarms, not mystery boxes
Record manufacturer, exact model, manufacture date, serial or batch information when present, power type and the model-specific manual. Look for clear listing or certification information required by your jurisdiction, then confirm it through the certifier or manufacturer rather than trusting a cropped marketplace badge. Search current CPSC recalls and safety warnings for the exact model before purchase and periodically afterward.
Choose power around the failure modes of the home. A plug-in or hardwired unit needs the backup specified by its design; a battery-only unit needs accessible replacement or sealed-life information. Digital displays, voice alerts and app notifications can add context, but they do not replace a loud local alarm or prove sensor performance. A smart-home connection is an extra channel, not the escape plan.
Combination smoke-and-CO alarms can reduce wall clutter, but the placement rules for smoke and CO are not identical in every situation. Confirm that one location and one device satisfy both the manual and local code. Do not buy a combination unit merely because it is cheaper than understanding two systems.
Build the testing and replacement record
The CPSC recommends testing CO alarms monthly and replacing batteries annually. The exact unit may use a sealed battery or require another battery schedule, so follow its manual and replace a low-battery device promptly. The test button checks functions described by the maker; it does not certify that every air path, room condition or household behavior is safe.
Create a one-page inventory with location, model, power source, install date, last monthly test, battery schedule and replace-by or end-of-life date. Put the next test on a recurring household calendar. If an alarm chirps, identify the pattern from the manual rather than removing the battery and promising to investigate later.
Replace a damaged, painted-over, contaminated, recalled or end-of-life alarm. Keep manuals and model records in the home emergency document file, but leave operating instructions where occupants can reach them. When moving into a home or rental, test the system and document questions immediately; do not assume a mounted device is powered, current or correctly located.
Control the sources alarms cannot excuse
The CPSC says never to run a portable generator inside a home or garage, even with doors and windows open. Use it outdoors at least twenty feet from the home with exhaust directed away. Never bring a charcoal grill indoors or into a garage, and never use a gas range or oven to heat the home. An alarm is not permission to shrink these boundaries.
Have heating equipment, chimneys and vents inspected and serviced annually by a trained technician. Keep vehicle and engine exhaust out of enclosed or attached spaces, and keep exterior vents clear. After storms or snow, inspect from a safe location and use qualified service when a vent, appliance or fuel system is damaged or uncertain.
Power outages create predictable pressure to improvise. Decide before the outage where the generator can operate, how the cord reaches without changing the exhaust boundary and where fuel is stored legally and safely. Add the CO alarm check to the same seasonal routine as the generator, furnace and emergency lighting.
Write an exit-first response
If a CO alarm sounds or poisoning is suspected, move everyone outside into fresh air and call 911. The CPSC explicitly advises getting outside first. Do not silence the alarm and walk room to room looking for a source, open windows as a substitute for leaving or send one person back inside for pets, documents or the suspected appliance.
Tell emergency dispatch that a carbon-monoxide alarm sounded or exposure is suspected and follow instructions. Symptoms such as headache, dizziness, weakness, nausea, vomiting, sleepiness or confusion increase urgency, but the absence of symptoms does not make an alarm safe to ignore. Do not re-enter until emergency officials say it is safe.
Rehearse two exits and an outdoor meeting point. Include children, older adults, people with disabilities, overnight guests and pets in the plan without assigning anyone a dangerous rescue role. After an incident, preserve model information and service records, and have the source and alarm system evaluated by appropriate professionals before normal use resumes.
Frequently asked questions
Where should carbon-monoxide alarms be installed?
CPSC guidance recommends them on every level of the home and outside sleeping areas. Follow the exact alarm manual and local law for room location, height, spacing and any additional requirements.
How often should a CO alarm be tested?
The CPSC recommends monthly testing. Follow the exact model’s instructions for the test procedure, battery schedule and end-of-life replacement.
Are interconnected CO alarms worth considering?
Yes. The CPSC says interconnected CO alarms are best because when one sounds, all sound. Confirm exact-device compatibility and install them according to the manufacturer and local code.
What should I do if the alarm sounds?
Get everyone outside into fresh air and call 911. Do not search for the source or re-enter until emergency officials say it is safe.
Sources and further reading
Claims checked against these official or professional sources on September 14, 2026.
- U.S. Consumer Product Safety Commission — Carbon Monoxide Information CenterFederal safety guidance on CO hazards, generator distance, alarm coverage, symptoms and emergency response.
- U.S. Consumer Product Safety Commission — CO AlarmsCurrent federal recommendations for locations, monthly tests, annual battery replacement and combination alarms.
- U.S. Consumer Product Safety Commission — Protect Your Family From CO PoisoningSource-control, interconnected-alarm, symptom and fresh-air guidance for the household plan.