Asked by: Keith Stephenson, Walsall

Smelling salts (ammonium carbonate) have been used since at least the 17th century to revive a patient from a faint. They work because the ammonia gas irritates the lungs and triggers an inhalation reflex, which alters the breathing patterns and elevates blood oxygen levels.

With ordinary sleep, it is quite possible to be woken by the smell of coffee or frying bacon, which stimulates the appetite and raises arousal levels.

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luis villazon
Luis VillazonQ&A expert

Luis trained as a zoologist, but now works as a science and technology educator. In his spare time he builds 3D-printed robots, in the hope that he will be spared when the revolution inevitably comes.

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