Where do smells go? © Getty Images

Where do smells go?

Pee-yew, what’s that smell?! Luckily all aromas get less over time thanks to a weakening concentration of scent molecules.

Asked by: Martin Ogilvie, Norwich 

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Smells ‘disappear’ when the aroma molecules disperse in the air to a concentration below your detection threshold. Your nose is more sensitive to some compounds than others: the eggy smell of hydrogen sulphide is detectable at concentrations of two parts per billion, while nail varnish remover (acetone) needs to be 50,000 times more concentrated before you can smell it. Some aroma molecules may also chemically react in the air to form a different compound that you are less sensitive to.

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