Carbon Monoxide


Carbon monoxide (CO) is a colourless, odourless, and tasteless gas generated by incomplete combustion of carbon molecules. It is also known as Carbonic oxide, Carbon oxide, Exhaust gas, and Flue gas. It is less dense than air. When gasoline, wood, propane, charcoal, or any other fuel is burnt, it produces carbon monoxide. Improperly vented appliances and engines, especially in a tightly sealed or enclosed setting, can collect dangerous levels of carbon monoxide.

Carbon monoxide poisoning is a distinct risk for victims of fire and smoke inhalation; however, accidental and suicide exposures are also prevalent.


  • Cooking stoves
  • Ovens
  • Gas clothes dryers
  • Gas water heaters
  • Furnaces
  • Space heaters
  • Stoves
  • Fireplaces
  • Pool heaters
  • Automobiles, trucks, campers, buses
  • Industrial forklifts
  • Motorcycles, ATVs
  • Ice skating rink resurfacing machines
  • Boats
  • Generators
  • Stoves
  • Lanterns
  • Grills
  • Lawn mowers
  • Snow blowers
  • Chainsaws
  • Power washers
  • Construction equipment


The gas is easily absorbed via the alveolus and has a higher affinity for haemoglobin than oxygen. Because oxygen is displaced from haemoglobin, oxygen transport is reduced, resulting in tissue hypoxia. Only around 1% of carbon monoxide is converted to carbon dioxide, thus it is mostly eliminated by respiration. The percentage of haemoglobin that has been coupled with carbon monoxide to create carboxyhemoglobin can be used to assess the degree of carbon monoxide exposure.

Signs and Symptoms

Headaches, dizziness, nausea, and vomiting are common symptoms of mild to moderate CO poisoning. Chest discomfort, dyspnea, syncope, convulsions, and coma are all symptoms of severe poisoning. Misdiagnosis is prevalent due to the diverse and unclear symptoms of carbon monoxide poisoning.

Mild (COHb less than 30%) Poisonings

  • Headache,
  • Nausea,
  • Vomiting,
  • Dizziness,
  • Exertional dyspnoea

Moderate (COHb between 30 to 40%) Poisonings

  • Chest pain,
  • Blurred vision,
  • Confusion,
  • Weakness,
  • Increasing dyspnoea,
  • Tachycardia,
  • Tachypnoea,
  • Staxia,
  • Severe headache,
  • Syncope,
  • Flushing,
  • Cyanosis,
  • Perspiration,
  • Decreased vigilance,
  • Diminished manual dexterity,
  • Impaired sensorimotor task performance,
  • Prolonged reaction time,
  • Difficulty thinking,
  • Impaired judgement,
  • Loss of muscular control,
  • Tinnitus or roaring in the ears,
  • Drowsiness,
  • Hallucinations, and,
  • Cardiovascular toxicity

Severe (COHb more than 40%) Poisoning

  • Trismus,
  • Muscle spasms,
  • Convulsions,
  • Palpitations,
  • Disorientation,
  • Ventricular dysrhythmias,
  • Hypotension,
  • Myocardial ischaemia,
  • Skin blisters,
  • Pulmonary oedema,
  • Respiratory failure,
  • Involuntary evacuations,
  • Coma,
  • Collapse, and,
  • Death

Lethal Exposure

This is generally stated in terms of the gas’s plasma concentration (carboxyhaemoglobin or COHb). COHb levels of more than 50 to 60 percent have the potential to be fatal.

Tests For Diagnosis

The tests used to identify carbon monoxide poisoning in blood are as follows:

  • Spectroscopic test
  • Hoppe-Seyler’s test
  • Kunkel’s test
  • Potassium ferrocyanide test
  • Katayama’s test, etc.

Other Tests:

  • Magnetic Resonance Imaging (MRI)
  • Computed Tomography (CT) Scan
  • Electrocardiogram (ECG)
  • Chest X-Ray


▪ Initial attention to the airway is the cornerstone of therapy.

▪ Take the person away from the source of the exposure.

▪ Use a tight-fitting high-flow reservoir face mask or an endotracheal tube to maintain a patent airway, fresh air, and orthobaric oxygen (100 percent oxygen at atmospheric pressure).

▪ The initial impact of oxygen is that it increases COHb dissociation.

▪ Hyperbaric O2 (HBO) at a pressure of 2-3 atmospheres combined with 5% CO2 can be administered by mask or intratracheal tube.

▪ If necessary, blood transfusion

▪ Gastric lavage to avoid pneumonia due to aspiration.

▪ Antibiotics and symptomatic treatment.

(Note: This is only for study purposes. Treatment should only performed by Medical Professionals)

Postmortem Findings

◼ 🍒Cherry red/pink colour skin, blood and tissue. This colour can be noticed in postmortem lividity regions. The colour is more visible in the inner corners of the lips, nail beds, tongue, and palms and soles of dark-skinned people.

◼ Cutaneous bullae (skin blisters) are occasionally found in the calves, buttocks, wrists, and knees.

◼ Pulmonary oedema.

◼ In CO poisoning, the white matter of the brain is reported to be harder than usual, and the brain holds its shape better following removal from the skull cavity.

Sources & References:

 Walker E, Hay A. Carbon monoxide poisoning is still an under recognised problem. BMJ 1999;319: 1082-3

Guy KM, Pimlott JK, Rogers M, Cross M. The new CO and smoke inhalation advisory service in the UK. Treatment of poisoning. Indoor Built Environment 1999;8: 199-202

Anonymous. Carbon monoxide, an old enemy forgot. Lancet 1981; ii: 75-6

J. George David, Poison – An Introduction for Forensic Investigators

Pillay VV, Modern Medical Toxicology, pp 359-364

Biswas Gautam, Review of Forensic Medicine & Toxicology , pp 516-518

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