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Carbon Monoxide: the invisible killer

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During an overheated reception, Maomao feels herself starting to nod off and notices that with so many people crowded together, there’s enough to make anyone suffocate. When several ladies faint, she doesn’t cry illness or bad omen: she orders them moved near the openings and explains that in a confined space, embers foul the air. In a few words, she diagnoses a poisoning and prescribes the right response, where others would have spoken of weakness or a curse.

The subject in depth

When a fuel burns, it combines with oxygen from the air. If oxygen is plentiful, combustion is complete and produces mostly carbon dioxide. But in an enclosed space, where the air doesn’t circulate well, oxygen runs short and combustion becomes incomplete: it then releases carbon monoxide [Wikipedia] . Embers in a closed room therefore combine two dangers at once: they deplete the air’s oxygen and load it with carbon monoxide.

Diagram of carbon monoxide binding to hemoglobin in place of oxygen
Carbon monoxide takes oxygen’s place on hemoglobin

This gas is particularly insidious because it is completely odorless, colorless, and non-irritating: nothing warns of its presence. Its danger lies in a chemical affinity. Hemoglobin, the protein in red blood cells that carries oxygen, binds to carbon monoxide about two hundred times more strongly than to oxygen. As soon as there is even a little in the air, it takes oxygen’s place on hemoglobin, which can no longer supply the organs. The body suffocates from the inside, even while it keeps breathing.

The symptoms are all the more treacherous because they resemble ordinary fatigue: headaches, nausea, dizziness, drowsiness, then loss of consciousness and, if exposure continues, death. Many victims fall asleep without understanding what is happening to them. Maomao’s response is precisely right: faced with a collective faintness in a heated, closed room, opening up and evacuating into the open air is exactly the correct move, because fresh air lets oxygen gradually reclaim its place on hemoglobin.

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