Why Smoke Smell Won’t Wake You Up

If a fire started while you were in a deep sleep, would the smell of smoke wake you

up? The science says: probably not. It turns out the human olfactory

system—our sense of smell—is a very poor "sentinel" during the night. While a simple sound,

like a tone or someone calling your name, can wake you up from almost any sleep stage,

our sense of smell essentially shuts down. In lab tests, participants in

deep sleep couldn't even smell strong, unpleasant odors like pyridine. However,

your brain is still selectively processing information; for example, a sleeping mother

is much more likely to hear her own baby’s cry than the cry of an unrelated infant.