Smoke Detector Placement:
Your Guide to Installing Carbon Monoxide and Fire Alarms

By: Sarah Sheppard

You may be diligent about unplugging your appliances and monitoring your candles, but there are a dozen reasons why home fires occur—electrical, heating, using a faulty appliance, overcooking your food—and mistakes happen. You can never be too careful when it comes to your safety.

U.S. fire departments respond to an average of one home fire every 88 seconds. With more than 300,000 fires occurring every year and the majority of them occurring in residential homes, fire protection is essential.

We’ll tell you how to properly install the right type of smoke detector in the best locations in your home, ensure that they work, and if a fire does happen, learn the best safety response.

Where to place smoke and carbon monoxide detectors

Carbon monoxide and smoke detector placement is just as important as having functioning alarms, so make sure you’re deliberate when installing your detectors. Having one unit for a three-story house, for instance, isn’t enough. Putting one alarm in the hallway on the second floor, but forgetting to put one on the first floor near the kitchen is problematic.

Laws vary state-by-state, but the National Fire Protection Association (NFPA) 72® National Fire Alarm and Signaling Code requires a minimum of at least one smoke alarm in every bedroom and one outside of each sleeping area, and no matter what, one on each level of the house.

We recommend placing detectors in all major areas of the home, including the basement, the dining room, the office, the kids’ playroom, and even on your porch. More than 9,000 home fires in the U.S. are caused by grills, on average.

The detector should be placed no more than 12 inches from the ceiling, at least 10 feet from a cooking appliance, and no more than 20 feet from a bedroom. Don’t place a smoke detector on a vaulted ceiling. If you have a vaulted or A-line ceiling, you’ll want the detector to be placed at the very top at the ceiling, not on the walls. Smoke detector placement can be challenging for a high ceiling, and may require a professional, a ladder, or a wired alarm system.

A smoke detector placement diagram is highly recommended to ensure your detectors are up to code. You can find them online, detailing the precise locations and distances.

Carbon monoxide detectors may not be required in all states, but the U.S. Consumer Producer Safety Commission recommends that you install one in the hallway outside of your bedroom area. If there is more than one sleeping area (one upstairs, one downstairs), you’ll want one for each area.

Before installing, you’ll want to make sure you follow the instructions included with your CO detector. There’s a myth that carbon monoxide detectors need to be placed in low areas of the home, but this isn’t true. You might want them plugged into outlets near the floor is so they’re easier to read, but it isn’t necessary for the detector to work properly.

To minimize false alarms, make sure you don’t install the CO alarm:

  • Too close to a bathroom, where a lot of humidity builds
  • In direct sunlight
  • In areas where air is common (near a fire-burning appliance, right below a fan, or right above a cooking appliance)

Ideally, these alarms should be installed throughout the home, including near the garage, where levels of carbon monoxide can rise, or the laundry room where you have electric machines, or on the stairwell between levels. It also doesn’t hurt to install one near the garage or in any place where there are fuel burning appliances, such as near the kitchen.

Types of smoke detectors

There are two types of smoke detectors, which serve two different purposes:

  • Ionization smoke alarms are used to detect flames. They are made with radioactive material that ionizes the air. When smoke disrupts the flow, it activates the alarm.
  • Photoelectric smoke alarms are used to detect flameless fires, also known as smoldering fires. These detectors are made with a light beam, and when the smoke gets in the way, it reflects light onto the light sensor that activates the alarm.

Ionization smoke alarms are likely to be triggered first in the case of fast flaming fires, but they don’t respond as quickly to smoldering fires.

Since you can’t predict which type of fire is going to erupt, you’ll want to ensure that you have both types of smoke alarms installed or buy one device that offers a combination of both ionization and photoelectric.

Carbon Monoxide alarm mounted to interior wall

Smoke detectors vs. carbon monoxide detectors

Without a fire alarm or carbon monoxide detector, you could breathe in harmful gasses without even realizing it. This is especially true in the case of carbon monoxide, which is a colorless, flameless toxic gas. Levels can rise for any number of reasons, including:

  • Using a wood-burning fireplace in a tight space
  • Using a furnace that’s been improperly installed
  • Using a portable generator
  • Using a ventless space heater
  • Leaving your car running

The problem with carbon monoxide, which is present in fires, is that you won’t notice it without a detector. You could escape a fire, but still be poisoned by carbon monoxide inhalation, because you can’t actually see it. You could also experience poisoning without a fire ever occurring.

Signs of carbon monoxide poisoning include dizziness, flu-like symptoms, loss of muscle control, and shortness of breath, and can quickly become fatal, so make sure you have a properly installed carbon monoxide detector.

Every year, approximately 50,000 people in the U.S. visit the emergency department due to accidental carbon monoxide poisoning, and at least 430 people per year die from poisoning. The best way to protect yourself and prevent a poisoning is to buy a carbon monoxide detector or a combined detector.

Just remember: A smoke detector and a carbon monoxide detector are not the same, so don’t assume that having one means you don’t need the other.

How to install smoke detectors

Unlike standalone carbon monoxide detectors, which are typically plugged into an outlet, a smoke alarm (or combined CO and smoke alarm) requires a more complicated installation process. You can easily install a battery-powered detector yourself with this step-by-step process:

  • Ensure that your detector has properly working batteries.
  • Mark a drill point on your wall or ceiling.
  • Drill the holes into the ceiling.
  • Make sure the smoke detector unit is separated from its frame before screwing the baseplate into the ceiling.
  • Attach the frame.
  • Test the detector to make sure it works.

Some detectors have adhesives attached, so you easily stick them to the wall. If you don’t want to install the detector yourself, you can pay for professional installation. This is important if you’ve purchased a hard-wire smoke detector.

Professional smoke detector installation costs an average of $65 per alarm for residential areas. Having a professional install the alarms can remove any fear that you’ve installed it incorrectly.

Whether you use a professional or not, you’ll want to test the smoke detector right away—and keep testing it every month thereafter. Typically, the batteries are replaced once every six months, but sometimes they need to be replaced sooner.

How to test smoke detectors

Once you’ve decided on your smoke detector placement and have properly installed the device, you’ll want to test it. All you have to do is use the test button to ensure that the alarm works. If you have interconnected alarms (which the NFPA 72 National Fire Alarm and Signaling Code requires), you’ll want to make sure all of them go off.

If you want to be even more certain that the alarm works, light a match or a candle, and hold it up to the detector to see if it triggers the alarm. You can also use an aerosol product. Hold it about two feet away and spray parallel to the wall.

You’ll know it’s time to replace your batteries or your alarm if the sound is weak or nonexistent. Smoke detectors should be loud enough to wake you, should you be sleeping when they go off. A carbon monoxide detector works the same way. If you’re using a standalone device, it might even beep or chirp persistently to notify you of a dying battery.

Hand installing Smoke detector on wood ceiling inside the house

How to respond to an active fire alarm

The purpose of a smoke detector is to alert you immediately when smoke or fire begins. No matter what type of fire you’re dealing with—slow, smoldering fire, or a rapidly spreading flame fire—you’ll need to know how to respond quickly, efficiently, and safely. Establishing a fire escape plan far in advance is important, especially if you have a family. Children practice fire drills at school, but should also practice them at home.

This is the proper home fire escape plan, according to the NFPA:

  • Know all possible exits (doors and windows) in all rooms. To be up to code, all rooms require at least one exit, which can include an egress window.
  • Make sure all exits are easily accessible. Don’t put furniture against doorways or block windows. If your windows have safety bars, make sure you have emergency release devices nearby.
  • Choose an outside meeting place that is a safe distance from the home, like a light post or a neighbor’s house.
  • Make sure you can see the house from the street, so emergency personnel have easy access.
  • Make sure all members of your family know the plan, including older children. If there is a young child or someone with a disability in the home, make sure there is a plan to assist them. You’ll want to consider your fire exit strategy as you childproof the home.
  • Know the number for the fire department and have it readily accessible, like on the refrigerator or stored on your cell phone.

A 2018 Red Cross Survey reveals that 40% of people believe they are more likely to win the lottery or get struck by lightning than experience a home fire, and yet, 40% of people have forgotten to turn off a stove or oven while cooking, which is the leading cause of home fires.

The more prepared you are for the hypothetical, the better. Running a drill or going through hypothetical situations can help. They goal is to escape the home as quickly as possible in the safest way possible, and unfortunately, you can’t predict where a fire will erupt or how fast it will spread.

If you live in an apartment building or if you’re “stuck” during an active fire, you’ll need to seal yourself in place. Here’s what to do:

  • Close any door that exists between you and the fire.
  • Block any openings, like the space between the door and the floor.
  • Cover any air vents that exist.
  • Open any windows to let fresh air in.
  • Call the fire department.

If you have the ability to escape—even with active flames—you’ll want to stay low to the floor and move under the flames, if necessary. Smoke and fire will rise, so the lower you can be and the quicker you can move, the better. Block your face, if possible, to prevent smoke inhalation.

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