The spread of smell, also known as olfactory diffusion, occurs when molecules of a substance, called odorants, are released into the air and travel through the nose to the olfactory receptors. Olfaction, or the sense of smell, is the ability to detect and distinguish different odors.
The spread of smell can be described as a combination of diffusion and convection. Diffusion is the random movement of molecules from an area of higher concentration to an area of lower concentration. In this case, the odorant molecules will move from the source of the smell to the surrounding area. Convection is the movement of molecules caused by a difference in temperature or wind. In this case, the odorant molecules will be carried by the air flow to farther places.
The intensity of a smell is also a factor to consider. The concentration of odorant molecules in the air will determine how strong a smell is perceived. The closer you are to the source, the stronger the smell will be.
Additionally, the environment can affect the spread of smell. For example, in enclosed spaces, the smell may linger longer because there is less airflow to disperse the odorant molecules. On the other hand, in open spaces, the smell may dissipate more quickly because there is more airflow to carry the odorant molecules away.
It's also worth mentioning that the sense of smell is subjective and can vary depending on an individual's olfactory receptors sensitivity and experience.