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Carbon monoxide

Carbon monoxide

What are the dangers?

The physical properties of carbon monoxide (CO) 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
  • is a neutral oxide which burns in air to give carbon dioxide
  • it is a good reducing agent.

CO is an important industrial gas widely used as a fuel and as 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 environments. 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 oxyhaemoglobin, 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 it replaces the oxygen and forms a substance called carboxyhaemoglobin.

Poisoning occurs by:

Haemoglobin 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.

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 inhalationadepends on the length of exposure:

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 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.

Advice on choosing and locating a carbon monoxide alarm.


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