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How can a person know if carbon monoxide is in their house?

Carbon monoxide (CO) is an odorless, colorless gas that can be deadly if inhaled. Knowing the signs of a carbon monoxide leak and taking proper precautions can help prevent poisoning and save lives.

What is Carbon Monoxide?

Carbon monoxide is a toxic gas that is produced when fuels such as gasoline, propane, natural gas, oil, wood, or charcoal burn incompletely. When these fuels burn, they produce carbon dioxide and carbon monoxide. While carbon dioxide can be dangerous in high concentrations, carbon monoxide is much more poisonous.

Carbon monoxide is dangerous because it binds to the hemoglobin in red blood cells much more easily than oxygen does. Hemoglobin is responsible for carrying oxygen throughout the body. When carbon monoxide attaches to hemoglobin, it reduces the amount of oxygen being circulated in the bloodstream. This oxygen deficiency can have severe effects on the heart and brain which require high amounts of oxygen to function properly.

What are the Sources of Carbon Monoxide in a Home?

There are several potential sources of carbon monoxide inside a home:

  • Gas appliances – Furnaces, water heaters, stoves, and ovens can leak carbon monoxide if they are not properly vented or malfunctioning.
  • Fireplaces and wood stoves – Using a fireplace or wood stove without proper ventilation can cause a buildup of carbon monoxide inside.
  • Portable generators or gas powered equipment – Running items like portable generators, charcoal grills, or propane camping stoves indoors or in enclosed areas can lead to dangerous levels of carbon monoxide.
  • Car exhaust – Cars left running in attached garages can leak carbon monoxide into a home.
  • Tobacco smoke – Lighting charcoal or tobacco products like cigarettes inside can be a source of carbon monoxide.

Faulty or improperly installed gas appliances are one of the most common causes of carbon monoxide leaking into a home. Good ventilation when using combustion appliances and avoiding idling cars in garages are important ways to reduce carbon monoxide exposure in the home.

What are the Symptoms of Carbon Monoxide Poisoning?

At low concentrations, carbon monoxide poisoning can be difficult to diagnose because its symptoms mimic other common ailments like the flu or food poisoning. At higher concentrations, carbon monoxide can be fatal within minutes. Here are the most common symptoms of CO poisoning:

  • Headaches – One of the earliest signs of carbon monoxide poisoning are frequent or persistent headaches.
  • Dizziness – A sense of dizziness or vertigo is a common symptom of moderate CO poisoning.
  • Nausea – Nausea and vomiting may occur as carbon monoxide builds up in the body.
  • Confusion and disorientation – Exposure can lead to confusion, disorientation, and an inability to think clearly.
  • Fatigue – Unusual fatigue is one of the most common symptoms reported from carbon monoxide.
  • Shortness of breath – The oxygen deprivation from CO can result in shortness of breath and rapid breathing.
  • Vision problems – Carbon monoxide poisoning may lead to blurred vision or temporary blindness.
  • Loss of consciousness – At very high concentrations, CO poisoning can result in seizures, coma, and death.

The symptoms of mild carbon monoxide poisoning are very similar to the flu or other illnesses, so it is easy to mistake them for something less serious. If multiple household members are experiencing these symptoms at the same time, it may indicate there is a dangerous amount of carbon monoxide in the home.

What are the Long Term Effects of Carbon Monoxide Exposure?

In addition to acute poisoning, long-term low-level exposure to carbon monoxide can have severe neurological effects that may not appear until weeks or months later. These can include:

  • Personality changes
  • Memory loss
  • Cognitive and emotional disturbances
  • Speech impairments
  • Sensory and motor deficits
  • Blindness
  • Hearing loss
  • Gait abnormalities
  • Loss of muscle control
  • Seizures
  • Psychosis

Children, pregnant women, the elderly, and people with existing heart or respiratory conditions are at an increased risk for these long-term effects. Even if the initial poisoning seems mild, it is important to seek medical attention if carbon monoxide exposure is suspected, as damage can continue to occur over time.

How to Detect Carbon Monoxide in the Home

Here are some methods for detecting dangerous levels of carbon monoxide in the home:

Carbon Monoxide Detectors

CO detectors are devices that alarm when they detect elevated levels of the gas. They are inexpensive, easy to find at hardware stores, and an important safeguard against carbon monoxide poisoning. The Consumer Product Safety Commission recommends placing a CO detector on each level of the home and near every sleeping area. Detectors should be replaced every 5-7 years.

Symptom Onset

Pay attention to the onset of carbon monoxide poisoning symptoms like dizziness, nausea, and confusion, especially if more than one person is experiencing them. The simultaneous nature of the symptoms are an important clue that CO could be involved.

Dead Pet Birds

Birds and other small pets are more sensitive to carbon monoxide than humans. A dead pet bird or other small animal may indicate the presence of carbon monoxide before people display symptoms.

Soot Buildup

Check gas burning appliances like stoves, ovens, and water heaters for any black soot or exhaust buildup around the unit. Soot accumulation often occurs when fuels are burning incompletely, which is when CO is produced.

Yellow Flames

Yellow or orange flames coming from a gas appliance may indicate carbon monoxide production. Properly adjusted burners should always produce blue flames.

Testing with a CO Meter

CO meters can precisely measure the concentration of carbon monoxide in the air. They can help locate the source by detecting higher levels near faulty appliances. Most fire departments have CO meters and can test a residence if poisoning is suspected.

What to Do if Carbon Monoxide is Detected

If a carbon monoxide leak is suspected or detected, the following steps should be taken immediately:

  1. Evacuate the building and get everyone into fresh air.
  2. Call 911 to alert emergency responders.
  3. Contact the fire department to test CO levels if a meter is unavailable.
  4. Call a qualified technician to inspect all appliances and identify the source of the leak.
  5. Do not re-enter the building until cleared by emergency responders.
  6. Seek medical attention if anyone is experiencing symptoms of CO poisoning.

Avoiding further exposure and getting medical help promptly provides the best chance of recovery from carbon monoxide poisoning. After a leak, a qualified professional must inspect appliances, identify the cause, and certify it is safe before re-occupying a building. Taking measures to prevent future leaks is also critical.

How to Prevent Carbon Monoxide Exposure

Safety measures like proper appliance maintenance, CO detector installation, and ventilation can help prevent the buildup of dangerous carbon monoxide levels in the home.

Install CO Detectors

Carbon monoxide detectors provide an important alarm when levels of CO rise past safe levels. Ensuring detectors are installed and working properly on every level of the home provides constant monitoring for a possible leak.

Proper Installation and Maintenance of Gas Appliances

Gas powered furnaces, water heaters, stoves, and other appliances should only be installed and serviced by qualified professionals. Performing regular maintenance checks and tuning up appliances each year helps keep them running safely and efficiently.

Ventilation When Using Combustion Appliances

Always use exhaust fans when cooking on gas stoves or baking in gas ovens. Running appliances like fireplaces, kerosene space heaters, and generators only in well-ventilated areas prevents CO from accumulating.

Avoid Idling Cars in Attached Garages

Pull cars and trucks into the driveway or garage and turn off the engine immediately to prevent exhaust and carbon monoxide from being drawn indoors.

Do Not Use Gas Appliances if their Flames are Yellow or Orange

Yellow or orange flame indicates inefficient fuel combustion and means that carbon monoxide is being produced. Have any malfunctioning natural gas appliances inspected and serviced immediately.

Install Carbon Monoxide Alarms

CO alarms provide an extra layer of safety, alerting residents to high levels before life-threatening symptoms occur. Place them on every floor of the home according to manufacturer recommendations.

Do Not Heat Your Home with a Gas Oven

Gas ovens are designed for cooking, not heating. Prolonged use of a gas oven without ventilation can be dangerous.

Avoid Using Fuel-burning Devices like Charcoal Grills Indoors

Only use grills, camping stoves, generators and similar items in well-ventilated outdoor areas to allow dangerous exhaust and CO to dissipate.


Carbon monoxide poisoning is entirely preventable with proper safety precautions. Installing CO detectors, maintaining fuel-burning appliances, avoiding engine exhaust indoors, and providing adequate ventilation whenever combustion appliances are in use are the best ways to protect against dangerous carbon monoxide exposure in the home. Recognizing the signs of CO poisoning and taking immediate action if it is suspected can also mean the difference between life and death in severe cases of exposure.