The Sages enacted the recitation of a berakha on smelling fragrance on Saturday night, because after Shabbat our spirits are despondent over the departure of the neshama yeteira. In order to revive them, we smell fragrance, which, according to the Sages, brings joy to the soul. Even one who does not feel pain at the departure of Shabbat will come to appreciate Shabbat’s greatness and realize that he should feel sorrow at its end, and that he should revive his soul with something aromatic.
One makes a berakha over fragrance following Shabbat, but not following Yom Tov, because on Yom Tov we are not granted a neshama yeteira. Additionally, when Yom Tov begins on Saturday night, one does not make the berakha over fragrance, because the joy of Yom Tov and its foods serve to comfort the soul (SA 491:1 and MB).
Similarly, one does not make the berakha over fragrance after Yom Kippur. Since we fast on Yom Kippur, there is no neshama yeteira, and there is not much sorrow at the conclusion of Yom Kippur (SA 624:3).
All those listening to havdala must smell the fragrance; therefore the person reciting havdala should wait until all listeners have smelled the fragrance, and only afterward continue with the berakha over fire. If the person making havdala continues to the next berakha before some listeners have a chance to smell the fragrance, they should listen to the next berakhot, and smell the fragrance afterward. One unable to smell does not make the berakha over the fragrance (SA 297:5; MB 13; SSK 61:8).
As people are generally aware, the Sages instituted different berakhot for different types of fragrance. If the fragrance comes from a tree or shrub, the berakha is “borei atzei vesamim” (“Who creates fragrant trees”). If it comes from an herb, one recites “borei isvei vesamim” (“Who creates fragrant herbs”). If the fragrance is from a fruit, one recites “ha-noten rei’aĥ tov ba-peirot” (“Who gives fruit a good scent”). If the source of the fragrance is inorganic or from an animal, one recites “borei minei vesamim” (“Who creates types of fragrance”). However, when it comes to havdala, the Ashkenazic custom is to always say “borei minei vesamim,” since most people are not experts on different types of fragrances and their respective berakhot, and if one mistakenly recites “borei isvei vesamim” over something from a tree, or “borei atzei vesamim” over an herb, he has not fulfilled his obligation. Therefore, the custom is to recite “borei minei vesamim” because, be-di’avad, it covers all fragrances. The Sephardic custom, in contrast, is to recite the berakha appropriate for the specific type of fragrance. For example, when using myrtle or rosemary, one recites “borei atzei vesamim” (MB 216:39; 297:1; Kaf Ha-ĥayim 297:31; Peninei Halakha: Berakhot 14:1, 5).
A berakha is recited over fragrances whose purpose is to give off a pleasing scent. However, no berakha is recited over fragrances whose purpose is to get rid of a bad smell, such as restroom air fresheners or deodorants (Peninei Halakha: Berakhot 14:3).
Regarding synthetic fragrances, some say that no berakha is recited, because the substance does not naturally smell good; the pleasing aroma is created by an artificial process. In practice, it seems proper that one who wishes to recite “borei minei vesamim” over it may do so, since ultimately the chemical properties that enabled the manufacture of this pleasing scent were created by God and it thus warrants a berakha (Peninei Halakha: Berakhot 14:2-3 and n. 3).
Some enhance the smelling of besamim by using the etrog that they used on Sukkot; since it was used for a mitzva, it is fitting to make a berakha on it at havdala. Cloves are stuck into the etrog to enhance its smell and preserve it (based on Rema 297:4). Since the resulting scent is the product of two types of fragrance (fruit and tree), according to all customs one recites “borei minei vesamim” over it (MB 216:39).