Put a carbon monoxide (CO) detector on every level of your home and in a central spot outside each sleeping area. Keep it away from kitchens, fuel-burning appliances and heating vents. Mount it the way the manufacturer's instructions say, because height depends on the model. If you can only buy one for now, put it near the bedrooms, where you need to hear it most.
This guide covers the details: which rooms and hallways work, which spots cause false alarms or missed readings, how many detectors a typical house needs, and when it makes sense to have an electrician wire them in.
TL;DR
- Install a separate CO alarm on each level of the home, and one in a central location outside each sleeping area.
- If you only have one, place it near the bedrooms and make sure it is loud enough to wake you.
- Keep alarms out of kitchens, away from fuel-burning appliances and heating vents, and never behind furniture or draperies.
- Follow the manufacturer's instructions for mounting height and spacing, and check local codes.
- Test monthly, and interconnect alarms when you can so one sounding triggers them all.
Table of Contents
- Where carbon monoxide detectors go in a home
- How high to mount a CO detector
- Where not to put a CO detector
- How many CO detectors does a home need?
- Interconnect and test the alarms
- Plug-in, battery or hardwired?
- What we see in the field
- Perspective: placement is a wiring question too
- When to call an electrician
- A quick placement checklist
- FAQ
- Sources
Where carbon monoxide detectors go in a home
Three federal and national safety bodies give nearly the same answer, which makes this easier than it looks.
- The EPA says each floor of the home needs a separate detector, and that a single detector belongs near the sleeping areas.
- The Consumer Product Safety Commission says CO alarms should be installed on every level of the home and outside sleeping areas.
- The NFPA says alarms belong in a central location outside each sleeping area and on every level of the home.
Carbon monoxide is odorless and colorless, so the alarm is the only warning you get. That is why the bedroom hallway matters most: you are asleep, and the alarm has to wake you.
Outside the bedrooms
"Outside each sleeping area" means the hallway or common space just beyond the bedroom doors. In a small house with all bedrooms off one hall, one alarm in that hall covers the whole sleeping zone. If bedrooms sit at opposite ends of the house, or on different floors, each group needs its own alarm.
The EPA adds that the alarm should be loud enough to wake you. Test that with the door closed. If you sleep with a fan or white-noise machine running and the hallway alarm is faint, move it closer or add one.
On every level
The EPA factsheet says to place CO alarms in a central location on every level of the home's livable space, including the basement. A finished basement with a gas furnace, water heater or fireplace is a common source of CO, and it is also where people spend time.
The CPSC takes a slightly different line: CO alarms generally should not be installed in attics or basements unless those areas contain a sleeping area. The two statements are easy to reconcile in practice. A basement you live in or sleep in gets an alarm. A storage-only crawl space or attic does not need one, and an alarm installed too close to a furnace may nuisance-trip. When in doubt, read the alarm's instructions and your local code.
Rooms with fuel-burning appliances
Gas furnaces, water heaters, fireplaces, stoves and dryers, plus attached garages, are the usual sources. An alarm on the same level as the appliance, in a hallway or adjoining room, is a better choice than one hung next to it. We cover the distance rules below.
How high to mount a CO detector
People search for a magic number, and there isn't one. Here is what the official sources say:
- NFPA says to follow the manufacturer's instructions for placement and mounting height.
- The CPSC says alarms may be installed in a plug-in receptacle or high on a wall, and that hardwired and plug-in alarms should have battery backup.
Some older advice says CO is lighter than air and the alarm must go on the ceiling. Others say it mixes evenly and low placement is fine. Because models differ in sensor design and the labs that list them test them for a specific installation, the instruction sheet that came with your alarm is the rule. Combination smoke and CO units are a special case: smoke rises, so those are normally mounted high, and the manual will say exactly where.
A practical way to handle it:
- Read the placement section of the manual before you pick a spot.
- Choose the location by the room rules (outside bedrooms, each level).
- Mount at the height the manual gives. If it lists a range, stay within it.
- Keep the alarm where you can reach it to test and silence it, and where you can see its display if it has one.
Plug-in models sit at outlet height by design. That is fine, as long as nothing blocks them. Which brings us to the places to avoid.
Where not to put a CO detector
The CPSC says not to install CO alarms in kitchens or above fuel-burning appliances, and to avoid locations near heating vents or where furniture or draperies could cover them.
| Location | Why to avoid it |
|---|---|
| Kitchen | Cooking can produce brief CO and fumes that trip the alarm, and the alarm is not meant for this space |
| Directly above a furnace, water heater or stove | A brief burst on startup can cause a false alarm |
| Near heating vents | Moving air can disturb the reading and the sensor |
| Behind furniture or draperies | Air cannot reach the sensor, and you may not hear it |
| Humid areas such as bathrooms | Moisture can affect many alarms, so check your manual |
| Direct sunlight or very hot or cold spots | Outside the temperature range most manuals allow |
On distance, the EPA says alarms belong at least 15 feet from fuel-burning appliances, and that you should follow manufacturer instructions and applicable laws and building codes. Fifteen feet is a useful default for hallways and living areas. If your furnace closet opens to a hallway that is also the only route to the bedrooms, the manual's guidance and your local code decide the exact spot.
If you want to understand why furnaces cause so many problems in the first place, a carbon monoxide and furnace safety guide explains how combustion appliances produce CO and what to keep an eye on between service visits.
How many CO detectors does a home need?
The rule is one per level, plus coverage for each sleeping area. Here is what that looks like in typical houses.
| Home | Minimum alarms | Where |
|---|---|---|
| Single-story, bedrooms in one hall | 1 | In the hall outside the bedrooms |
| Single-story, bedrooms in two wings | 2 | One outside each wing |
| Two-story, bedrooms upstairs | 2 | Upstairs hall, and a central spot on the main floor |
| Two-story with finished basement | 3 | Upstairs hall, main floor, and a central spot in the basement |
| Home with attached garage | Same as above | Add one on the level closest to the garage, outside the garage door's path |
These are working minimums built from the official guidance, not a legal number for your address. The count that actually applies to you depends on the code in force where you live, and on how your home is laid out.
Two notes on the count:
- The CPSC points out that its home placement differs from smoke alarm placement. Smoke alarms are also recommended inside each bedroom, while CO alarms are listed for each level and outside sleeping areas. Don't assume your smoke alarm layout is a CO layout.
- A combination smoke and CO unit counts for both jobs, but only if it sits where both need it. A bedroom smoke alarm that is also CO-capable does not replace the hallway CO alarm.
Interconnect and test the alarms
Once the alarms are in the right places, they need to talk to each other. NFPA recommends interconnecting all CO alarms so that when one sounds, they all sound. In a two-story house, that means a basement alarm can wake the people upstairs.
The EPA recommends testing alarms monthly and interconnecting them when possible. A monthly check takes under a minute per unit: press the test button, hear the horn, move on. Put it on the same day as your smoke alarm test so it sticks.
When buying, NFPA recommends choosing an alarm that carries the label of a recognized testing laboratory. Look for the mark on the box and on the unit itself.
Plug-in, battery or hardwired?
The CPSC says hardwired and plug-in alarms should have battery backup, so they work during a power outage. That matters more than people think: outages are when portable generators and space heaters come out, and those are leading CO sources. If you run a portable generator, our guide on keeping portable generators 30 feet from the home explains how to place it and connect it safely.
| Type | Strengths | Watch for |
|---|---|---|
| Battery | Goes anywhere, no wiring | Dead batteries, chirping, forgotten replacement |
| Plug-in with battery backup | Easy to install, no ladder | Blocked outlets, furniture, limited spots |
| Hardwired with battery backup | Interconnects cleanly across floors, no outlet needed | Needs an electrician for new locations |
Hardwired alarms are the cleanest choice for whole-house interconnection, particularly during a remodel or when you open walls anyway.
What we see in the field
We see the same placement mistakes repeatedly: an alarm that was fine when installed, then blocked by a bookcase; a unit hung beside a furnace closet and silenced after a false alarm; a basement with a gas appliance and no alarm at all.
Our approach is to look at the whole house before choosing a spot. That includes where the fuel-burning equipment is, where people sleep, and how the alarm will be powered and linked.
Perspective: placement is a wiring question too
Most guides treat CO placement as a shopping decision. At Guardian, we treat it as part of the home's electrical plan. The right location for an alarm is often not where an outlet already exists, and the best interconnection is one that runs over wire, not over a hope that batteries are fresh.
We start with a consultation, and we encourage customers to send photos of hallways, mechanical closets, the garage entry and the basement stairs. That lets us suggest locations before anyone climbs a ladder. Photos also reveal the things that cause trouble later: a vent right where the alarm would go, a bedroom door that opens onto a dead-end wall, or a furnace closet opening onto the only route to the bedrooms.
Our rule of thumb is simple. Follow the manual, follow the code, and pick locations for the people who sleep in the house. If that points to a spot with no power, we run it. Mounting height and spacing come from the manufacturer, not from us, and we won't improvise around them.
— Logan
When to call an electrician
You can mount a battery alarm with a screwdriver. Call a licensed electrician when:
- You want hardwired, interconnected alarms on several levels.
- You are remodeling or building new and walls are open, which is the cheapest time to run wire.
- An existing alarm circuit trips, chirps for no reason, or does not link.
- You are replacing an older hardwired unit and want it matched to a new model.
- You manage rental or commercial property and need consistent coverage across units.
If your alarm sounds, don't troubleshoot it. Get everyone outside into fresh air and call 911 or your fire department. Call a service technician only after the emergency is cleared.
How we can help
We handle smoke and CO alarm installation in Myrtle Beach, including placement planning, new wiring and interconnection. If an existing system is misbehaving, our smoke and CO alarm electrical service is the place to start. Estimates are free, and pricing depends on the job, so we don't publish a flat rate. Tell us about your house through our services page and send photos if you have them.
If you are planning other electrical work at the same time, such as a panel upgrade or lighting and ceiling fan installation, it is usually efficient to schedule the alarm wiring in the same visit.
A quick placement checklist
- Count your levels, including any basement you use.
- Find every sleeping area and the hallway outside it.
- Mark fuel-burning appliances: furnace, water heater, stove, dryer, fireplace, garage.
- Keep alarms at least 15 feet from those appliances where the layout allows, and out of kitchens and bathrooms.
- Check each spot for vents, curtains, furniture and direct sun.
- Mount per the manufacturer's instructions.
- Interconnect, if the model allows.
- Test monthly.
FAQ
Where is the best place for a single CO detector?
Near the sleeping areas, in a hallway just outside the bedrooms, according to the EPA. Make sure the alarm is loud enough to wake you with the bedroom door closed. Treat one alarm as a starting point and add one for each level.
Should a CO detector be on the ceiling or low on the wall?
Follow the manufacturer's instructions, which is what NFPA advises. The CPSC says alarms can be placed in a plug-in receptacle or high on a wall. Combination smoke and CO units are usually mounted high, but your model's manual decides.
Do I need a CO detector in every bedroom?
Not necessarily. The CPSC recommends CO alarms on every level and outside sleeping areas, while smoke alarms are also recommended inside each bedroom. A hallway alarm that wakes you through a closed door generally meets the intent. Check local code for your address, since some rules differ.
Can I put a CO detector in the kitchen or next to the furnace?
No. The CPSC says not to install them in kitchens or above fuel-burning appliances. The EPA gives 15 feet from fuel-burning appliances as a guide. Put the alarm in a nearby hallway or living area instead.
How often should I test my CO alarms?
Monthly, per the EPA. Press the test button and confirm the horn sounds, and replace the unit when the manufacturer says it has reached the end of its life.
Sources
- Where should I place a carbon monoxide detector? | US EPA
- Carbon Monoxide Poisoning: Protect Your Family and Yourself | US EPA
- Carbon Monoxide Questions and Answers | CPSC
- CO Alarms | CPSC
- Carbon Monoxide safety | NFPA