The phrase "study at smell" can be replaced with a variety of synonyms. One potential substitution might be "analyze aromatic qualities". This phrase is more scientific in nature and might be appropriate when studying the chemical makeup of different odors. Another option could be "examine olfactory properties". This phrase emphasizes the sensory experience of detecting different odors and could be more appropriate when studying the impact of smells on human behavior or psychology. Finally, one might use the phrase "explore scents" to describe a more casual or artistic approach to studying smells, perhaps in the context of perfume-making or flavor development.