HomeHealth articlescarbon monoxide poisoningHow Does Carbon Monoxide Poisoning Affect Us?

Carbon monoxide is a deadly, colorless, odorless, poisonous gas. This article illustrates the effects and poisoning of carbon monoxide.

Written by

Dr. Vidyasri. N

Medically reviewed by

Neha Suryawanshi

Published At November 18, 2022
Reviewed AtNovember 25, 2022


Carbon monoxide (CO) is a poisonous gas produced from the incomplete burning of natural gas or other products containing carbon. It includes exhaust, fires, heaters, and factory emissions. When people are exposed to CO gas, the CO molecules bind and displace the oxygen into carboxyhemoglobin in their bodies, leading to poisoning.

What Are the Problems With Carbon Monoxide?

Since carbon monoxide (CO) has no odor, color, or taste, it cannot be detected by our senses. Though dangerous gas concentrations build up indoors, they cannot be identified until people become ill. When people become sick, the symptoms are similar to normal flu, which leads to ignoring the early signs of CO poisoning.

What Are the Indoor Sources of Carbon Monoxide?

Homes with fuel-burning appliances or attached garages have carbon monoxide problems. Most common sources include:

  • Water heaters.

  • Furnaces or boilers.

  • Gas stoves and ovens.

  • Tobacco smoke.

  • Wood stoves.

  • Grills, generators, lawn equipment, and power tools.

  • Cloth dryers.

  • Motor vehicles

Exposure to low levels of carbon monoxide can occur outdoors near roads, as it is formed by the exhaust of petrol and diesel-powered motor vehicles. Hence, parking areas can also be a source of carbon monoxide.

  • In developed countries, emissions from faulty, incorrectly installed, poorly ventilated or cooking appliances that burn fossil fuels.

  • In developing countries, the burning of biomass fuels and tobacco smoke are the most commonly exposed sources indoors.

  • Clogged chimneys, decorative fireplaces, wood-burning fireplaces, and supplementary heaters without properly working safety features also cause carbon monoxide emissions in indoor spaces. Incomplete oxidation during combustion also leads to high concentrations of carbon monoxide in indoor spaces.

  • Combining low-grade solid fuel and biofuels in a small stove or fireplace can generate high carbon monoxide emissions. Initially, the pollutants released are dominated by particulate matter (elemental and organic carbon), but carbon monoxide dominates in the end.

  • Combustion of high-grade fuels such as natural gas, propane, and butane produces much less carbon monoxide, providing sufficient air to ensure complete combustion.

  • Incense burning also contributes to carbon monoxide exposure in cultures where incense is burned frequently.

  • When cooking with open fires, public or residential garages and primitive kitchens record the highest carbon monoxide levels. Aside from open fire cooking with solid fuels, the most common sources of elevated carbon monoxide concentrations in indoor air are unvented gas appliances, tobacco smoking, and heavy traffic.

  • The lowest carbon monoxide concentrations are in churches and schools at some distance (greater than 500 meters) from heavy traffic.

  • Anthropogenic emissions (from land-use conversion and fossil fuel combustion) account for about two-thirds of the carbon monoxide in the atmosphere. Natural emissions account for the remaining one-third.

  • Small amounts are produced endogenously in the human body.

  • Carbon monoxide intoxication can be caused by single or repetitive exposure, whereas carbon monoxide poisoning can even result in death.

What Is the Toxicokinetic Mechanism of Carbon Monoxide?

  • Hemoglobin combines more effectively with carbon monoxide than with oxygen. It binds 220 times more intensely than it does with oxygen.

  • In a standard room temperature with air (21 % oxygen), the half-life of carbon monoxide is 320 minutes.

  • In the presence of oxygen (100 %), the half-life of carbon monoxide is less than 90 minutes.

  • In hyperbaric oxygen with the presence of three ATA (atmospheric pressure absolute), the half-life of carbon monoxide is reduced to 23 minutes. Hence, hyperbaric oxygen therapy is the only definitive therapy for carbon monoxide poisoning.

What Are the Symptoms of Carbon Monoxide Poisoning?

Excess inhalation of carbon monoxide (CO) results in carbon monoxide poisoning. Symptoms include:

  • Chest pain (particularly in patients with angina).

  • Convulsions.

  • Coma.

  • Confusion.

  • Fatigue.

  • Headache.

  • Drowsiness.

  • Fainting.

  • Irritability.

  • Dizziness.

  • Impaired judgment.

  • Hyperactivity.

  • Low blood pressure.

  • Muscle weakness.

  • Unconsciousness.

  • Nausea.

  • Vomiting.

  • Rapid heartbeat.

  • Shock.

  • Breathing problems, shortness of breath, or rapid breathing.

Many of these symptoms occur with viral illnesses; carbon monoxide poisoning is often confused with these conditions. Unfortunately, this may result in delayed diagnosis and treatment.

How Are Indoor and Outdoor Carbon Monoxide Ratios Calculated?

Carbon monoxide is an unreactive gas under ambient air conditions and is not absorbed by ventilation system filters or building materials. Thus, in the absence of indoor carbon monoxide sources, the indoor air concentration is the same as the ventilated or infiltrating outdoor air. With these conditions, the Indoor: Outdoor (I:0) carbon monoxide ratio should be 1:0.

But when measured practically, I:0 vary for two reasons:

  • Indoor sources like gas appliances and tobacco smoking can increase I:0 ratios.

  • The outdoor air carbon monoxide concentration at the measurement point may vary high or low to the concentration at the point of ventilation air intake. Even in the absence of any indoor sources, when observed for 15 minutes, the ratio varies from 0.2 to 4.1, and the daily value of I:0 ranges from 0.4 to 1.2.

How to Prevent It?

1. Adequately Maintained and Vent Fuel-Burning Appliances:

All fuel-burning appliances used in the home should be properly vented to the outside. It is necessary to check for the following problems-

  • Absence of an upward draft in the chimney.
  • Streaks of soot in the fuel-burning places.
  • Rusting on flue pipes.

  • Damaged bricks at the top of the chimney.

  • Orange or yellow flame in combustion appliances.

  • Avoid using ovens to heat the home.

2. Maintaining Carbon Monoxide Alarms:

Every home should have at least one operational carbon monoxide alarm within 10 feet of every room used for sleeping.

What Is the Treatment of Carbon Monoxide Poisoning?

  • The initial approach for carbon monoxide poisoning is to provide supplemental oxygen as early as possible.

  • Hyperbaric oxygen treatment should be provided at the earliest in patients with elevated carboxyhemoglobin levels, cardiac ischemia, tachycardia, and hypotension. Positive outcomes occur when the patients receive their first treatment within six hours of the poisoning event. Even then, 40 % of patients can progress to chronic neurocognitive impairment. Hence neuropsychological evaluation should be carried out one to two months after recovery.


Carbon monoxide has various harmful effects on humans. Its toxicity and even low level of poisoning can lead to life-threatening situations and even death. Hence preventive measures like awareness of carbon monoxide poisoning and the installation of carbon monoxide detectors can aid in avoiding these conditions.

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Neha Suryawanshi
Neha Suryawanshi


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