How to Test for Carbon Monoxide in Your Home

carbon monoxide alarm

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Carbon monoxide (CO) is often called the silent killer because it is odorless, tasteless, and invisible, making this toxic gas one of the most overlooked dangers in homes. The Centers for Disease Control and Prevention estimates that annually close to 450 people die and 20,000 people are admitted to the emergency room as a result of unintentional carbon monoxide poisoning. Both numbers spike during winter months when heating systems are working overtime. To keep you and your family safe, understand the many sources of carbon monoxide in your home, as well as ways to test for carbon monoxide.

Safety Considerations

If you cannot adequately check your home on your own for carbon monoxide, contact a local inspection service. If you feel that you may have been exposed to carbon monoxide, see your doctor immediately.

Project Metrics

  • Working Time: 15 minutes
  • Total Time: 30 minutes
  • Skill Level: Beginner
  • Material Cost: $100 to $200

What You Will Need


Portable carbon monoxide meter


All portable carbon monoxide meters work differently. Consult manufacturer instructions for details about your own meter.

Power the Meter

Turn on the meter with the "On" button. Let the meter fully power up.

Set to Zero

Your portable carbon monoxide meter will have some type of zero-point setting to establish a base point. Do this outdoors or in a room that you know is free of carbon monoxide.

Run the Self-Test

Most portable carbon monoxide meters have a diagnostic self-test to calibrate the meter. It may take from three to five minutes to complete the test.

Test the Area of Suspected Carbon Monoxide

Go to the area that you believe has carbon monoxide and run the meter until it reaches at least a 90-percent reading (in many models).

Check the Meter Readings

Carbon monoxide meters will report back to you in various ways: with sounds, lights, or on-screen readings. A 0-1 PPM (parts per million) reading is considered to be a normal background level, with 35 PPM being the OSHA/NIOSH maximum 8-hour exposure limit.


If you suspect the presence of carbon monoxide in your home, leave the home immediately and call the fire department or a professional on-site air testing company. Open all of the windows and doors and turn off all stoves, your HVAC system, and the water heater.

Alternative Methods of Testing for Carbon Monoxide Gas

Indoor Air Quality Test

The ultimate and most accurate way to detect the presence of carbon monoxide in the home is with an indoor air quality test. Private companies are available to perform indoor air quality and improvement tests that include carbon monoxide testing. Some municipal fire departments and utility companies will come to your home and check for carbon monoxide for free or at reduced rates.

The main tool used in these tests is an electronic portable toxic multi-gas monitor. This device differs from the consumer-level carbon monoxide detectors in that it can be calibrated to detect trace carbon monoxide gas from nearly 0 PPM and at increments as small as 1 PPM. In addition to testing for carbon monoxide, most of the private companies will test for other harmful pollutants, such as mold, allergens, radon, formaldehyde, and more.

HVAC Combustion Analysis

If you or the testing company believe that the HVAC system is the source of the carbon monoxide, you can contract with an HVAC company to check your system with a combustion analyzer. A combustion analyzer is an electronic device that tests vented gasses directly coming from furnaces to ensure that the ratio of carbon monoxide to oxygen remains within a safe range. A combustion analyzer tests only gasses combusted directly from a furnace, not overall air quality. The device tends to be too expensive and limited in use for most do-it-yourselfers to purchase. Many HVAC companies and on-site air quality testing companies do not own combustion analyzers, so check with the company in advance before they come to your house.

Consumer-Level Carbon Monoxide Gas Detector

The easiest way to see if there is carbon monoxide inside your home is with a carbon monoxide detector (this tool is different from a carbon monoxide meter). In fact, many building codes require a carbon monoxide gas detector. If you do not have carbon monoxide gas detectors in your home, not only are you putting you and your family at risk, but an inspector could also flag you and prevent the sale of your home or condo.

Such off-the-shelf carbon monoxide gas detectors are valuable but they should be viewed only as passive carbon monoxide detectors. They are not as accurate as portable toxic multi-gas monitors or portable carbon monoxide gas meters since they typically measure only down to 30 PPM. The aim of these carbon monoxide gas detectors, too, is to act as the last layer of warning to protect individuals in habitable areas such as bedrooms, dining rooms, living areas, and hallways. These carbon monoxide gas detectors are not meant to detect carbon monoxide gas at suspected locations of origins such as furnace rooms or even in kitchens. In fact, most of these carbon monoxide gas detectors should be installed beyond a radius specified by the detectors' instructions: 5 feet or more beyond cooking appliances and 20 feet or more beyond furnaces, for example.

Sources of Carbon Monoxide in the Home

Carbon monoxide is produced by gas, oil, coal, charcoal, and wood fuels that have burned incompletely. Carbon monoxide is more common among older furnaces as well as full HVAC systems and gas water heaters that have not been properly vented. Electric furnaces, electric water heaters, electric ovens, and all other electrically powered devices operating normally do not produce carbon monoxide. 

While artificial heating is by no means the only source of carbon monoxide in the home, it is a major contributor. Besides carbon monoxide gas being produced by furnaces not installed or venting correctly, it can come from other fuel-fired sources, including but not limited to:

  • Gas ranges and stoves
  • Gas clothes dryers
  • Gas water heaters
  • Portable fuel-burning space heaters
  • Fireplaces
  • Wood-burning stoves
  • Vehicles running in an attached garage
  • Charcoal/gas grilles

Symptoms of Carbon Monoxide Gas Poisoning

People who have suffered carbon monoxide gas poisoning describe a general flu-like feeling with symptoms such as:

  • Headache
  • Dizziness
  • Weakness
  • Upset stomach
  • Vomiting
  • Chest pain
  • Confusion

Carbon monoxide poisoning is even more deceptive since it coincides with the winter months when people more often experience the flu. A number of signs that distinguish carbon monoxide poisoning from the flu include:

  • Everyone in the home is sick at the same time
  • Pets are sick as well
  • You feel better when you leave the house

While everyone is prone to carbon monoxide poisoning, infants, the elderly, and those with heart disease, anemia, and breathing problems are more likely to get sick.