should You Put Carbon Monoxide Detectors High or Low

There’s always a constant debate among experts on the ideal placement height of Carbon monoxide (CO) detectors. Some say that carbon monoxide concentrates close to the floor; therefore, CO detectors are more effective closer to the ground. Other experts recommend installing CO detectors higher up because the gas is lighter than air and rises like smoke.

This difference in opinions brings a lot of confusion, especially among homeowners installing CO alarms for the first time. All they want to know is whether should you put carbon monoxide detectors high or low?

A carbon monoxide detector will sense spikes in the gas levels whether you place it high near the ceiling, at eye level, or low near the floor. The reason is that CO is lighter than air, but the difference is negligible. As a result, the gas tends to diffuse evenly throughout a room.

That said, all manufacturers of CO detectors build their devices differently. For this reason, most of them have placement recommendations that ensure their device works optimally. Therefore, always read and follow the manufacturer’s placement recommendations during the installation of the alarm for guaranteed safety.

Where Should a Carbon Monoxide Detector Be Placed?

Before making a decision on whether to mount a CO detector high or low, you must first know in which room to place them. You must install them in areas approved by the laws in your state or follow the directives of the National Fire Protection Association (NFPA).

The following is a list of general areas to place carbon monoxide detectors in every home. 

  • In All Sleeping Areas

should you put carbon monoxide detectors high or low
A Carbon Monoxide Detector

Carbon monoxide poisoning can occur at any time, but it is especially dangerous at night. Symptoms of the poisoning are often mild; therefore, you may not feel them while you sleep. For this reason, it’s wise to have a CO detector in every sleeping area to warn occupants of danger.

If you cannot afford to have at least one device in every bedroom, ensure that you install the CO detector in the hallways connecting the bedrooms. This way, the alarms are close enough to be heard by everyone, including the deep sleepers. 

One alarm in every standard-sized hallway is enough. However, if your hallway is longer than 40 feet, place CO detectors at both ends for maximum protection.

  • On Every Floor of the Residence

Having a carbon monoxide detector on every floor of your building will ensure that you get a warning no matter where you are inside. The alarms will be even more effective if they are interlinked so that when one goes off, all of them sound simultaneously.

The basement of your home also counts as a separate floor if you’ve set it up as a sleeping room. It is also the area where most homeowners put water heaters, furnaces, and laundry machines, which are all potential sources of carbon monoxide. 

  • Near an Attached Garage

Car engines produce a lot of carbon monoxide, and there’s often the risk of leaving the car running in the garage by mistake. Such a mistake could cost the lives of many people, especially if the garage is connected to your home.

For this reason, it is wise to place a CO detector at least 10 feet from the garage door leading into your home. This way, you will be notified if there’s a sudden spike in carbon monoxide levels in the garage, allowing you to get your family to safety in good time.

  • In the living area

It is good to have a CO detector in your living room, especially if it is on a different floor from the sleeping areas. It is even more mandatory to mount a device in the living room if you have a gas- or wood-burning fireplace.

  • In the Kitchen

The kitchen is like the pandora’s box of CO poisoning. It usually has gas stoves and ovens, wood stoves, and water heaters, among many other appliances that produce carbon monoxide. Therefore, it stands to reason that every kitchen must have a CO detector to sound an alarm in case the gas levels spike.

  • Where the Detector’s Manufacturer Recommends

Every carbon monoxide detector is created slightly differently; therefore, it makes sense that there may be slight differences in where to mount them. Luckily, some manufacturers provide specific placement instructions for their devices to ensure they serve you efficiently. So, if you’re not sure where to install your CO detector, Follow the manual instructions.

Where to Avoid Mounting a Carbon Monoxide Detector

Even though it is important to have enough CO detectors in the right spots, it is equally important to avoid mounting them in areas where they will trigger false alarms. So, here are four places you must never put a carbon monoxide detector.

  • Too Close to Fuel-burning appliances.

It is good to have a CO detector in rooms with appliances like a fireplace, a gas-powered stove, or a gas-burning furnace. However, you must never put the device too close to the appliances, or else you will be disturbed by false alarms all the time. Here’s how.

Most of these appliances produce safe levels of CO gas upon start-up and continue producing trace amounts as they burn. So, if you mount a detector too close to the source, you risk triggering the alarm even when there’s no danger.

If you want a CO detector to work optimally, install it at least 5-15 feet away from the fuel-burning appliances. 

  • Behind Curtains or Furniture

Never place a CO detector where there are obstructive items because they will prevent the device from performing optimally. Things like curtains or furniture could prevent the gas from reaching the device’s sensors causing the alarm to sound when it’s too late.

  • In Bathrooms or the Path of Flowing Air

Most CO detector manufacturers design their devices to work within specific humidity and temperature levels. Any spikes in these areas are sure to trigger false alarms. For this reason, it is best not to put a CO detector in your bathroom, near an open window, or an air vent or fan. 

  • Within the Reach of Small Children and Pets

One of the best heights to mount a CO detector, especially one with a digital display, is at eye level. However, you must ensure that you place the device high where a child or pet cannot reach it, even if they stand on furniture. Apart from potentially dismantling the detector, a child may press the test button and set off a false alarm.

How to Install a Carbon Monoxide Detector 

You Will Need 

  • A carbon monoxide detector (battery-powered or plug-in)
  • A pencil
  • Drill bit
  • Power drill
  • Hammer
  • Batteries
  • Plastic wall anchors

Step 1: Install the detector’s mounting base

Carbon monoxide detectors have a mounting base that’s separate from its sensor. This base has two screw holes that make it easy to fix to the wall or ceiling.

  • Place the mounting base against the wall or ceiling, then use a pencil to mark the screw holes.
  • Use a drill to make holes where you placed the pencil marks. Ensure that the drill bit is slightly smaller than the supplied screw anchors to ensure a snug fit for the screws.
  • Next, use a hammer to tap the screw anchors into the drilled holes gently.
  • Drive two screws partially into the wall anchors and then line them up with the mounting base. 
  • Finally, twist the mounting base into place and then use a screwdriver to tauten the screws.

Note: If you have a plug-in CO detector, ensure that you install the mounting base close to the nearest wall outlet.

Step 2: Install The Batteries 

Open the CO detector’s battery door to reveal the battery bay, then put in the provided batteries. Ensure you follow the markings inside the bay and align the battery’s positive(+) and negative(-) terminals accordingly.

Step 3: Attach the Carbon monoxide detector to the base

Hold the CO detector over the mounting base and then twist it clockwise until it snaps into place. If it is a battery-powered device, it may light up or beep once to show that it’s working. If the detector doesn’t beep, press the test button to know if it works correctly.

  • If you have a wired CO detector, plug it into an outlet, and you’re good to go.

Here’s How to Install Carbon Monoxide Detector:

What Number Is Too High On a Carbon Monoxide Detector?

Carbon monoxide concentration is measured in parts per million (PPM), and any level of exposure can cause poisoning. However, the risk of harm depends on the amount of CO and how long you’re exposed to it.

A concentration of 50 PPM and below is considered low-level risk exposure, provided you’re not exposed to it for more than 8 hours. 51 PPM-100 PPM is considered mid-level risk exposure, and you may start experiencing poisoning symptoms in as little as 4 hours. Any number above 100 PPM is considered too high on a carbon monoxide detector and could be fatal within hours or even minutes of exposure.

Below, I’ll discuss the symptoms of exposure to different CO concentration levels and the duration it takes the symptoms to manifest.

  • 50 PPM: Low-level Risk Exposure

Most people won’t experience any poisoning symptoms from exposure to concentrations between 1-50 PPM. However, poisoning symptoms will start to show after 8 hours of exposure.

That said, people with pre-existing conditions like heart disease or immune issues may experience a little more intensity in the symptoms of their particular affliction. The symptoms may manifest even when the CO levels are as low as 30 PPM. 

Most carbon monoxide alarms will only sound when the gas concentration is 50 PPM because it is the standard low-risk exposure level. However, it leaves people with pre-existing health conditions at a disadvantage because they start experiencing the effects of the gas much sooner.

For this reason, it is best to buy a CO alarm with ultra-sensitive detection technology. Such devices can detect carbon monoxide levels below 30 PPM, allowing you to keep everyone safe.

  • 200 PPM: High-level Risk Exposure

When concentration hits 200 PPM, you will begin to experience poisoning symptoms within 2-3 hours. You will feel dizziness, mild headaches, and nausea, and your body will be too weak to move quickly.

For people with pre-existing conditions, a 200 PPM concentration will put them in critical condition or even kill them within hours.

  • 400 PPM: High-level Risk Exposure

At 400 PPM, you will experience major frontal headaches within an hour or two. The dizziness, nausea, and weakness will also reach a peaking point, putting you in critical condition.

  • 800 PPM – 12,800 PPM: Dangerous Concentration Levels

Once the carbon monoxide concentration levels hit 800, you will experience dizziness, nausea, and weakness within 30 minutes. Convulsions may follow soon afterward and render you unconscious, and any prolonged exposure could prove fatal within minutes.

Tips to Protect Your Home From Dangerous Carbon Monoxide Levels

Many household appliances produce trace amounts of carbon monoxide, which could increase in concentration if you don’t take proper care. So, here are a few things you can do regularly or avoid to remain safe from this odorless gas.

  • Avoid smoking excessively inside your home as it could lead to carbon monoxide slowly building up inside your home.
  • Maintain flues and chimneys to prevent blockages, leaks, or disconnects. A block can prevent CO from escaping, creating a deadly concentration of the gas. Also, check for damaged chimney bricks or rusting flue pipes and replace or repair them accordingly.
  • Always have your heating system, water heater, and any fuel-burning appliance serviced by a qualified technician annually.
  • Avoid running your vehicle in an enclosed garage to prevent carbon monoxide levels from building up.
  • Don’t handle any fuel-burning appliance in an enclosed or unventilated space. Such appliances include generators, gas-powered grills, pressure washers, charcoal grills, portable camping stoves, etc.

How Do I Know If My Carbon Monoxide Detector Is Working?

You must regularly test your carbon monoxide detector to know if it works properly. Test the device’s circuitry once a month by pressing the “test” button and use a special tester spray annually to see if the device’s sensor is still functioning optimally.

Here, I’ll show you the correct way to do both tests to ensure the safety of everyone.

How to Test a Carbon Monoxide Detector Using a Tester Spray

Step 1: Purchase a CO Detector Tester Spray

CO detector sprays are readily available in most home improvement stores, but you can also find them online at an affordable price. They are usually canned carbon monoxide but are not dangerous if inhaled, provided you use them as instructed.

  • A can of CO detector spray costs between $8-$15 and can last you a few good years.

Step 2: Cover Your CO Detector With a Plastic Bag

The spray tester contains a minute concentration of carbon monoxide that would not set off even a standard CO alarm. For this reason, you must enclose the device with a plastic bag to confine the test spray close to the device. Ensure that both the CO alarm and the test spray nozzle are enclosed tightly for the best results.

  • Press the test spray’s nozzle for about 3-5 seconds to release enough carbon monoxide for the detector’s sensors to pick up.
  • If the sensor is working correctly, the alarm will sound within 15 minutes. However, if the spray doesn’t trigger the alarm, you may need to change the detector’s batteries or replace the unit altogether.

Note: Enclosing the CO detector in a plastic bag is an affordable way to conduct the test. However, you can also purchase or build a testing compartment that holds the test spray and seals around the device while you test it.

Step 3: Remove the Plastic Bag to Give the CO detector Fresh Air.

If your device is working properly, the alarm will continue to sound until the CO concentration around it dissipates. Therefore you must remove the plastic bag to allow fresh, clean air to enter the alarm’s sensors.

After removing the bag, press the detector’s test button to “hush” the alarm and then repeat the test at least once a year.

How to Test a CO Detector’s Circuitry

Start by pressing the test button on the CO detector. The appearance and location of CO alarm test buttons vary from device to device. However, most models have the test button located next to an LED light that flashes periodically.

If the detector’s circuitry is working correctly, the alarm should sound for about 3-5 seconds before turning off automatically. If the alarm doesn’t sound, then you should change the detector’s batteries and do the test again.

Note: Some carbon monoxide detectors have a sealed 10-year battery that cannot be changed. Such units must be replaced when the circuitry test does not trigger the alarm. Luckily, alarms with a sealed battery will beep periodically to let you know that it needs replacement.

How Long Does It Take for a CO Detector to Detect Carbon Monoxide?

It takes about 1 hour for a standard carbon monoxide detector to alert CO concentrations of 70 PPM and below. However, if the concentration is as high as 400 PPM and above, the detector’s alarm will trigger in as little as 5 minutes.

Below is a detailed list of how long specific CO concentrations take to trigger an alarm.

  • 40 PPM concentration can take up to 10 hours to trigger an alarm. The duration is longer than most because 40 PPM is considered a low-risk level of exposure.
  • 50 PPM concentration takes 8 hours to trigger the alarm. However, some units will detect the gas and sound an alarm within 4 hours.
  • 70 PPM concentration takes about 1 hour to trigger the alarm; however, some units may take up to 4 hours to detect the gas.
  • 150 PPM CO concentration will trigger an alarm in 10-50 minutes.
  • 400 PPM and above will take 4-15 minutes to trigger the alarm, depending on the unit you’ve installed.

Understanding CO Detector Beeps

Many assume that a CO detector will only beep when it detects dangerous levels of carbon monoxide. However, there are occassions where you may be dealing with a false alarm. For this reason, it is best to understand the types of beeps from a carbon monoxide alarm to avoid panic when it is unnecessary.

Here are the three common CO detector beeps that you must understand.

  • 4 beeps and a pause in a continuous cycle means that there’s a high level of carbon monoxide in the air, and you must seek fresh air and call 9-1-1 immediately.
  • 1 beep every minute, and a flashing LED indicates that the detector’s batteries are running out and need changing immediately. If a plug-in CO detector beeps every minute, it could mean its battery is loose, and you should check it.
  • 5 beeps every minute indicate that Your CO detector has reached the end of its life; hence you need to replace the whole unit.


Everyone agrees that having a carbon monoxide detector in your home is the best way to warn you in case of a CO leak. The National Fire Protection Association (NFPA) has even set national guidelines on where you should install the devices for maximum protection.

However, there’s still constant debate on whether the devices should be placed high, like smoke alarms, or at eye level where you can reach it. So I wrote this article to answer the burning question,

Should You Put Carbon Monoxide Detectors High or Low?

Carbon monoxide detectors will sense the gas’ presence whether you place them close to the ceiling or at eye level. Therefore, your main concern should be installing at least one device in all sleeping areas, on every floor, near an attached garage, and in the kitchen and living areas.

That said, some CO alarm manufacturers specify the best positioning of their units to ensure that they work optimally. So be sure to follow the device’s manual instructions during installation.

Thank you for reading this article, and I hope it has helped you decide on the correct height placement of your carbon monoxide detector. If you have more information to share or need me to clarify anything, please feel free to reach out in the comments below.

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