Carbon monoxide is dangerous when inhaled in excess. Comment on the statement.
Topic: Carbon monoxide poisoning
Answer
Carbon monoxide combines with HAEMOGLOBIN about 200-300 times more readily than oxygen does, forming a stable compound called CARBOXYHAEMOGLOBIN.
Because this combination is almost irreversible, the haemoglobin is no longer available to carry oxygen. The tissues are starved of oxygen, causing headache, dizziness, unconsciousness and, in excess, DEATH BY ASPHYXIATION.
Two marks: the MECHANISM (the affinity for haemoglobin) and the CONSEQUENCE (oxygen starvation).
The figure is what makes the answer precise: carbon monoxide binds 200-300 times more readily than oxygen, so even a small concentration in the air captures a large share of the haemoglobin.
WHY IT IS SO INSIDIOUS, worth a closing line: carbon monoxide is colourless, odourless and tasteless, so a victim gets no warning and simply becomes drowsy and loses consciousness. This is why charcoal stoves and generators must never be used in closed rooms, and why an idling car in a shut garage is lethal.
Its sources: incomplete combustion of fuels — vehicle exhaust, faulty heaters, burning coal, and cigarette smoke.