Carbon Monoxide Poisoning

When we talk about gases, carbon monoxide is no stranger who needs an introduction. Of recent, so much talk about climate change — which is caused by greenhouse gases — has been doing the rounds all over the world, and much of this talk borders around the dangers that gases like Carbon Monoxide pose for inhabitants of the environment, chief among which is poisoning. Thus, as inhabitants of the earth, it is important for us to understand, in its entirety, what is meant by ‘Carbon Monoxide poisoning’. But before delving into the crux of the matter, it is first pertinent to refresh our knowledge of carbon monoxide.

Basic Facts about Carbon Monoxide

Carbon monoxide, one of two inorganic gases formed from carbon, is an inorganic chemical compound containing one atom of Carbon and one of Oxygen (CO). Its largest source is the troposphere, where about 5 x 1012 kilograms is annually generated and released into the atmosphere. Non-natural sources include combustion in the absence of sufficient oxygen, volcanoes, and forest fires.

Despite its toxicity when concentrated in the blood above the 35ppm mark, it is produced during most of the animal metabolic activities. It is found in the atmosphere with a concentration of 0.003%, and it is an essential element in the formation of ground-level ozone.

Carbon monoxide is used in the chemical industry for the production of bulk chemicals, preservation of meat products, as a reducing agent in metallurgy for producing ores from metals and as a lasing medium in lasers. With this short introduction, you must have seen that CO is quite a useful gas; however, as useful as it may seem, it’s got few problems it causes, one of which is carbon monoxide poisoning. And this downside — poisoning — is the kernel of what we shall be discussing.

What is Carbon Monoxide Poisoning

Carbon monoxide poisoning, as the name may suggest, is a condition that arises from breathing in too much of the gas (above 35ppm concentration). It occurs either in an attempt to commit suicide or by accident, and is the most commonplace form of poisoning round the world; it has a death risk ranging from 2 to 30% among affected individuals.

Carbon monoxide poisoning is responsible for more than 20,000 visits to the emergency unit per year in America with more than 400 non-fire related deaths recorded every year. Most cases of poisoning occur during winter, especially from the fumes from portable generators during periods of a power cut.

Some of the earliest known documentation of carbon monoxide poisoning dates back to Aristotle(200B.C). Since then, two Roman Emperors, Julian, and Jovian suffered from carbon monoxide poisoning, with the latter even losing his life. During the Holocaust, too, gas vans containing Carbon monoxide was used by German Nazis to kill prisoners estimated to be over 700,000 in number. The treatment of this kind of poisoning started in 1868, and since then, the incidence of poisoning has reduced considerably.

Its Causes 

Carbon monoxide poisoning usually arises from the inhalation of carbon monoxide fumes from the exhaust pipe of vehicles; it could arise from the incomplete burning of fuel in cooking equipment or other appliances that use carbon compounds as fuel. Methylene chloride exposure can also be a cause of carbon monoxide poisoning.

In caves, poisoning could occur when carbon monoxide accumulates in enclosed chambers from the decomposition of organic matter which gives off carbon monoxide as a product. Carbon monoxide is given off in this case, instead of carbon dioxide, since there is not enough oxygen to oxidize the carbon monoxide so produced.

Furthermore, poisoning could also occur when an individual is exposed to dichloromethane, which is a major constituent of paint strippers and metabolizes to yield carbon monoxide gas in considerably high amounts. In coal mines too, incomplete combustion may occur with the coal (since coal is basically carbon), leading to afterdamp, a mixture of gases which is extremely toxic and can contain up to 3% CO. Such concentration of carbon monoxide gas is sufficient enough to kill after inhaling just once.

Medically, carbon monoxide poisoning is explained thus: carbon monoxide binds with hemoglobin, leading to the formation of carboxyhemoglobin (HbCO), which prevents hemoglobin from transporting oxygen effectively round the body. Basically, the more carbon monoxide is inhaled, the more the formation of carboxyhemoglobin and the more difficult it is for oxygen to be transported around the body.

Signs and Symptoms


Carbon monoxide poisoning, just like every other form of poisoning, has its signs and symptoms. But here, the symptoms vary based on the tolerance level of an individual to the gas. The tolerance level for carbon monoxide varies based on factors such as ventilation, existing cardiovascular disease, sickle cell anemia, and metabolic rate.

Depending on the concentration of carbon monoxide gas inhaled, symptoms of poisoning also vary. From concentrations above 35 ppm, there is an offset of a headache and dizziness after six hours of steady exposure to the gas; once this concentration reaches the 100ppm mark, slight headache begins after two hours of exposure. This slight headache leads to a loss of judgment within two hours of exposure to 200 ppm of the gas.

For much higher concentrations, such as 800 ppm, nausea, and convulsions set in just after 45 minutes of exposure to carbon monoxide and the individual become insensible after 2 hours. At the 3,200ppm mark, death can occur within 30 minutes and when the concentration doubles, respiratory arrest, and death in about 20 minutes. At 12,800 ppm death occurs in less than three minutes.

Symptoms develop in organs where oxygen is extremely important for normal functioning, such as the heart, the brain, and the spinal cord.  Acute poisoning usually comes with initial symptoms such as a headache, nausea, and fatigue which may degenerate to hallucination, low blood pressure, pneumonia, edema, and a host of other conditions. Chronic poisoning, on the other hand, usually leads to hearing disorders, temporary and permanent memory loss, learning impairment and coronary heart disease.



A number of symptoms of carbon monoxide poisoning also occur with many other conditions such as influenza, hence its diagnosis is difficult. However, carbon monoxide is generally diagnosed by ascertaining the level of carbon monoxide in the blood. This is done by obtaining the ratio of carboxyhemoglobin to hemoglobin in the blood.

Carboxyhemoglobin to hemoglobin ratio may stand at less than or equal to 0.05 or 5%, while for smokers, about 0.09 to 0.1 is perfectly normal, above which a person is diagnosed with poisoning.  A CO-oximeter is used to check for carboxyhemoglobin levels in the blood.


Public health experts continue to engage people on preventive measures to adopt in order to prevent poisoning, much of which borders on the need to adopt safety measures in the operation of appliances and combustion engines as well as the important roles carbon dioxide detectors play in preventing poisoning.

Gas appliances and equipment should be serviced at least twice every year to prevent eventual gas leakage, as carbon monoxide is odorless and tasteless, and as such cannot be detected easily.


The immediate treatment for sufferers of carbon monoxide poisoning involves removing them from the exposed areas to areas where there is adequate ventilation. This ensures that carbon monoxide is dissociated from carboxyhemoglobin, converting it back to hemoglobin. Unconscious patients should be given cardiopulmonary resuscitation immediately to prevent further complications, especially in pregnant women.

To hasten the dissociation of CO from carboxyhemoglobin, hyperbaric oxygen could be employed. Hyperbaric oxygen contains oxygen at three times the atmospheric pressure. This pressure helps to reduce the lifespan of carbon monoxide three times, from 80 to 26 minutes. It also boosts the transport of oxygen to the tissues and the blood.

Final Words…

The need for prevention and safety cannot be overemphasized as far as carbon monoxide poisoning is concerned. It’s extremely necessary to shield yourself and your loved ones from carbon monoxide as much as possible, as the symptoms could go so wild and deadly.