Ghrana pratyahara is difficult, as one gets accustomed to the smells around one. The smells arouse different responses in one. Take the fragrance of incense, you walk in and after a while you do not notice the smell anymore. This keeps happening, with the different smells. One smells them and then they are ignored.
For the sense of smell, we become aware of Raga and Dvesha. Raga is a desire for things that bring satisfaction. When we do not get what we want, we are angry. When we do get what we want, after a while we want more. Dvesha is aversion towards things that produce unpleasant experiences. Dvesha can cause us to suffer even when we are thinking about unpleasant experiences.
With smell, these two sources become active. If there is a foul smell, the nervous system reacts immediately.
So, close your eyes and allow the sense of smell to operate. Identify all the smells around you, without a reaction or a response. Just say that it is a pleasant smell or an unpleasant smell.
Your sense of smell is heightened and at the same time you are unaffected by it.
Learn more in my pratyahara series.
Aim Hrim Klim