Mindfulness of Breathing and the Sense of Smell
Traditional and modern meditations are full of breathing exercises. However, i have never heard of the sense of smell being used or even mentioned in any breathing awareness meditation. It seems to me that smell is the active ingredient of the breath. If i'm not aware of the smell, then it is only a narrow awareness of the breathing. It's like hearing electrical notes without the trumpet and violin tones. It's like seeing in black and white.
Hedgehogs and dogs would probably consider breathing, without smelling, to be a complete waste of time.
The sense of smell has a unique character, as do all the senses. One special aspect of the sense of smell, is that it is internal and external, inside and outside our bodies. We take it inside in a way we don't feel with sounds and sights. Sights are always perceived as outside us (we don't recognise the reflection on the retina). We may sometimes feel sounds pass through us, but this is not comparable with the smells which fill and empty us.