The smell of an agarbatti (incense stick) is detected through a biological and chemical process involving the olfactory system in the nose and the brain:

• When an agarbatti is burned, it releases volatile organic compounds (VOCs) — aromatic molecules — into the air due to the heating of its essential oils, resins, and fragrant herbs

• These VOCs travel through the air and enter the nasal cavity when we inhale

• Inside the upper part of the nasal cavity, specialized sensory cells called olfactory receptors bind to these odorant molecules

• Binding of odor molecules to olfactory receptors triggers chemical reactions that generate electrical impulses

• These electrical signals are transmitted via sensory neurons to the olfactory bulb, a part of the forebrain in the brain

• The olfactory bulb processes these signals and sends them to other brain regions, including the olfactory cortex, where the brain interprets the signals as a distinct smell — in this case, the fragrance of the agarbatti

• This interpretation allows us to consciously perceive and recognize the smell of the incense stick

In summary, the detection of an agarbatti’s smell is a complex interaction of chemical release, receptor binding, neural signaling, and brain processing that results in the perception of its characteristic fragrance