Carbon monoxide is dangerous because it

  • A. binds haemoglobin far more strongly than oxygen does and does not readily let go
  • B. dissolves the walls of the alveoli
  • C. destroys the red blood cells immediately
  • D. prevents the diaphragm from contracting

Explanation

Carbon monoxide has roughly two hundred times the affinity of oxygen for haemoglobin and forms stable carboxyhaemoglobin, so those binding sites are taken out of use and the blood carries far less oxygen even though it looks bright red. The victim feels no shortage of breath, because breathing is driven by carbon dioxide, which is why poisoning from a gas heater can be fatal during sleep.

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