What is Carbon Monoxide? - Effects & Overview

Instructor: Nicola McDougal

Nicky has taught a variety of chemistry courses at college level. Nicky has a PhD in Physical Chemistry.

Carbon monoxide is often called the silent killer, but do you know why? In this lesson we'll learn what carbon monoxide is, how it is formed and how it affects the body so silently. You can test your new knowledge with a quiz.

What is Carbon Monoxide?

Carbon monoxide (CO) is a highly toxic, colorless and odorless gas that is slightly less dense than air. It consists of one carbon atom and one oxygen atom bonded together by a triple bond.

Chemical structure of carbon monoxide. Notice the two pairs of non bonding electrons on both the carbon and oxygen atoms
chemical structure of carbon monoxide

This triple bond is very strong, and it is not possible to break the atoms apart so the molecule remains intact. Carbon monoxide is highly toxic to animals and humans, and air concentration levels of just 0.1% (1000 ppm) are considered dangerous.

The reason for this toxicity is the chemical structure of carbon monoxide. Looking at the diagram you can see that the molecule has 10 valence electrons. Six of these electrons are in the triple bond, and four more non-bonding electrons. These non-bonding electrons are highly reactive and give carbon monoxide the ability to bind to transition metals such as iron in hemoglobin, the oxygen-carrier protein in blood. Carbon monoxide binds very strongly to the Fe-center of hemoglobin, blocking the uptake of oxygen. This prevents oxygen from being transported around the body.

How is Carbon Monoxide Formed?

Carbon monoxide is naturally produced in the atmosphere during volcanic activity. A natural concentration of CO is about 0.1 ppm. However, in the modern world, CO is treated as a polluting gas produced by the incomplete combustion of carbon based fuels.

Combustion is the chemical process of burning, which is the rapid combination of fuel with oxygen to release energy in the form of heat of light. For example, the combustion of methane, under normal conditions, is shown below:

Methane combines with oxygen to form carbon dioxide and water during the combustion process
diagram of the combustion of methane to produce carbon dioxide and water

With a plentiful supply of oxygen, the main products of combustion are carbon dioxide and water. However, when the oxygen supply is limited, carbon monoxide is formed instead. If the oxygen is very limited, then black soot, which is just pure carbon, is formed in place of a carbon oxide gas.

Oxygen is the key to whether carbon monoxide is a significant combustion product. It is very important to understand that carbon monoxide can potentially be formed in a variety of common situations. For example, it can be formed by:

  • Anything that burns coal, gasoline, kerosene, oil, propane, or wood
  • Automobile engines
  • Charcoal grills (charcoal should never be burned indoors)
  • Indoor and portable heating systems
  • Portable propane heaters
  • Stoves (indoor and camp stoves)
  • Water heaters that use natural gas

Grilling should always be done outside so there is a plentiful supply of fresh air to avoid a build up of carbon monoxide
image of grilling on a bbq

Carbon monoxide from any of these activities can build up in places that do not have a good flow of fresh air. You can be poisoned by breathing them in.

Why is Carbon Monoxide so Dangerous?

Carbon monoxide has earned the nickname of 'silent killer' as it has no color, taste or smell. When you breathe in carbon monoxide it passes unnoticed into the bloodstream. Once there, it interferes with the ability of your hemoglobin to carry oxygen and your body becomes oxygen starved.

The most common signs of carbon monoxide poisoning are headache, dizziness, nausea, vomiting and confusion. It is often very hard to tell if someone has carbon monoxide poisoning because the symptoms are very similar to many other illnesses. People who are sleeping or intoxicated can die of carbon monoxide poisoning before they have symptoms. A CO detector can warn you if you have high levels of carbon monoxide in your home.

To unlock this lesson you must be a Study.com Member.
Create your account

Register to view this lesson

Are you a student or a teacher?

Unlock Your Education

See for yourself why 30 million people use Study.com

Become a Study.com member and start learning now.
Become a Member  Back
What teachers are saying about Study.com
Try it risk-free for 30 days

Earning College Credit

Did you know… We have over 200 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Transferring credit to the school of your choice

Not sure what college you want to attend yet? Study.com has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

Create an account to start this course today
Try it risk-free for 30 days!
Create an account
Support