The site for odour detection is

Nose is the first potential target for inhaled substances, except when one breathes through the mouth. Nose is important in odour detection. Interior parts of the nose warm, moisten, and filter air. This helps to protect the lungs from harm. Some inhaled material is trapped in the nasal cavity. The trapped material can, however, be transported from there to the throat, where it is swallowed. Nose blowing can also remove deposited material from the nose.