The human nose is capable of recognising up to a trillion different smells and is by far the best instrument, even scientifically, that we have to detect odours. Not all odours are pleasant however, as many who have spent time at waste management facilities and chemical plants can agree. Our noses are delicate instruments that can detect harmful molecules such as hydrogen sulphur in concentrations as low as 10 parts per billion, protecting us from prolonged exposure. Because when persistently exposed to bad odours, the wonder of the sense of smell can soon turn into a nightmare.
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