Why is Carbon Monoxide So Dangerous?

​As a home inspector, one of my top priorities is ensuring the safety of home occupants. One of the most dangerous and often overlooked threats in a home is carbon monoxide (CO). Known as the “silent killer,” carbon monoxide is an invisible, odorless, and tasteless gas that can be lethal if not properly detected and addressed. I remember learning about it from an old TV show called Rescue 911 and have done extensive research into why an otherwise harmless carbon and oxygen atom combine to become deadly to humans. 

Testing out my new gas analyzer, which detects a number of dangerous gases.

What Exactly is Carbon Monoxide?
CO is a byproduct of incomplete combustion. It is produced when fuels such as gas, oil, coal, or wood do not burn completely. Common household appliances, including furnaces, water heaters, gas stoves, fireplaces, and even cars running in an attached garage, can generate carbon monoxide.

Why is Carbon Monoxide Dangerous?
Carbon monoxide is so hazardous because it binds to hemoglobin (basically the body's air highway) more effectively than oxygen. When CO is inhaled, it prevents oxygen from being delivered to vital organs like the brain and heart. Even low-level exposure can cause symptoms, and prolonged exposure can be fatal. CO poisoning can frequently be mistaken for the flu.
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Common Myths About Carbon Monoxide
There are many misconceptions about CO that can lead to dangerous assumptions. Here are some of the most common myths:

1. Carbon monoxide has a smell. – CO is completely odorless, which is why detectors are essential. I have seen some claim that CO has a distinct smell like propane but this is FALSE. Propane only has a "rotten egg" smell because of an artificial additive known as methyl mercaptan and Carbon Monoxide has NO smell whatsoever. 
2. If I feel fine, there’s no CO in my home. – CO poisoning can happen gradually, and low levels of exposure may not cause immediate symptoms. Even with symptoms, they are frequently mistaken for colds, flus and food poisoning: while bedrest is great for these conditions, with CO poisoning going to sleep can be fatal! 
3. CO poisoning only happens in the winter. – While heating appliances are a common source, CO can be produced year-round from BBQS, vehicles, furnaces, and boilers.
4. Leaving a window open prevents CO poisoning. – While ventilation (such as from an HRV or ERV) certainly helps, it does not guarantee safety, as CO can still accumulate to dangerous levels.

How to Protect Your Home from Carbon Monoxide

1. Install Carbon Monoxide Detectors! – Not only should you place CO detectors on every level of your home, particularly near sleeping areas, they should be replaced after 5 years due to the breakdown of the electrochemical sensors. Doing pre-purchase inspections has shown be it is rare to find CO sensors under 5 years old. 
2. Regular Maintenance of Appliances – Have your heating system, water heater, and other fuel-burning appliances inspected annually by a professional. It's an upfront expense but you will save in the long run with reduced maintenance and breakdown costs. 
3. Ensure Proper Ventilation – Make sure all vents, chimneys, and flues are clear and properly ventilated. I always recommend a level 2 WETT inspection for all homebuyers even if for insurance purposes. 
4. Never Run Engines Indoors! – Do not leave cars, generators, or other fuel-burning equipment running in enclosed spaces, even with doors open. If it is too rainy to BBQ outside, it is too rainy to BBQ outside! 
5. Know the Signs of a CO Leak – If you or your family experience symptoms, evacuate immediately and seek fresh air. Like I mentioned previously, they can mimic common illnesses like the flu or food poisoning. 

​Carbon monoxide is a deadly hazard that homeowners cannot afford to ignore. By taking the proper precautions, you can protect yourself and your family from this invisible threat. Homeowners need to stay vigilant about maintenance and ventilation. One preventable tragedy is too many for this home inspector!