Myth Buster

What is carbon monoxide?

The physical properties of carbon monoxide are:

  • it is a colourless, odourless, neutral, gaseous oxide, which is highly poisonous.
  • it is sparingly soluble in water, but is soluble in ethanol and in benzene.
  • it has a relative density that is similar to air.

The chemical properties of carbon monoxide are that it is:

  • a flammable and highly toxic gas.
  • a neutral oxide which burns in air to give carbon dioxide.
  • a good reducing agent.
  • an important industrial gas widely used as a fuel
  • a reducing agent in the chemical industry.

Causes of poisoning

Carbon monoxide is produced when fuels are burned incompletely. This includes:

  • tobacco smoking
  • idling petrol
  • diesel powered engines
  • oil
  • wood
  • coal
  • paper
  • charcoal
  • kerosene
  • propane
  • butane
  • Even burning your toast or chops!

All these fuels are found in the domestic/recreational and working environment. The risk of poisoning from properly installed, ventilated and regularly maintained appliances is extremely low.

However, we spend approximately 80% of our time in enclosed spaces like the home, vehicle, caravan, holiday accommodation, office, workshop, boat even a tent, it follows that having improperly installed, maintained, or the incorrect operation or use of appliances which can create unsafe levels of CO could dramatically increase our risk of exposure.


Normally when you breathe, oxygen is absorbed from the lungs into the blood where it combines with hemoglobin to form oxyhemoglobin, which is then transported to organs, tissue and muscle. In the muscle oxygen is transferred to myoglobin to create oxymyoglobin.

However, when you inhale carbon monoxide replaces the oxygen and forms a substance called carboxyhemoglobin.

Poisoning occurs by:

  • Anoxia
    Hemoglobin has a much greater affinity for carbon monoxide than oxygen, a ratio of about 240:1 and 25:1 for myoglobin, thus a relatively low carbon monoxide concentration can replace a large number of oxygen molecules for our bodies use.
  • Hypoxia
    Oxygen that is absorbed cannot be released from the blood to the organs and tissues because carbon monoxide also increases the affinity of hemoglobin to oxygen.

Foetal haemoglobin has a higher affinity for CO than the mother. The effects of carbon monoxide inhalation depends on the length of exposure:

  • Acute
    The signs and symptoms of acute exposure may include headache, flushing, nausea, vertigo, weakness,  irritability, unconsciousness, and in persons with pre-existing heart disease and atherosclerosis, chest pain and leg pain.
  • Chronic
    Chronic exposure Is more difficult to diagnose than acute because the symptoms are more subtle, the  carboxyhemoglobin levels may be only slightly elevated. It results from exposure to lower concentrations  over an extended period anywhere from one week to months, maybe years. It can lead to long term and  permanent health problems with debilitating effects for the sufferer.

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The following symptoms could indicate carbon monoxide poisoning:

  • Headaches
  • Drowsiness
  • Dizziness
  • Nausea
  • Vomiting
  • Confusion
  • Weakness
  • Convulsions
  • Respiratory Problems
  • Concentration Problems
  • Behaviour Problems
  • Personality Change
  • Clumsiness
  • Severe Muscle Pains
  • Fast Heart Rate
  • Trembling
  • Vision Problems
  • Loss of Hearing
  • Walking Problems
  • Unconsciousness


These measures can help to prevent carbon monoxide poisoning:

  • All fuel burning appliances and associated flues/chimneys are installed by the appropriate, registered trades people.
  • the above are maintained and serviced in accordance with the manufacturers instructions
  • no-one modifies or tampers with any appliance, flue or chimney
  • your chimney is swept and inspected regularly
  • ventilation openings are not blocked and are free from vegetations
  • fit an audible CO alarm, certified to EN 50291
  • the CO alarm is tested when your appliances are.

All appliances should be correctly installed and maintained. A CO alarm is not a substitute!

What to do if you have been poisoned

If you believe you have been poisoned you should preferably seek medical attention at A&E. Inform medical staff you suspect you have been poisoned by CO and give all the information that you possibly can that makes you think this.

You should request an immediate blood test - you may have been poisoned but a delayed analysis could show a false negative.


  • Switch on or re-light any of your appliances until you have had them checked by the relevant trades people and you are assured they are safe.
  • Allow the removal of, or major works to any appliance found faulty without first taking advice.