Why do Catholics burn incense at Mass and at other times?

When placed on burning charcoal, incense produces a visible smoke and a recognizable aroma that fills the church. The smoke represents prayers going up to heaven and the sweet aroma reminds people of the sweetness of God’s divine mercy. Incense has been used in worship since pagan times. On a more practical level, incense was burned in the Middle Ages when churches didn’t have decent air circulation and parishioners didn’t wear deodorant. On a hot summer Sunday, the smell in the church became quite potent unless plenty of incense was burned.

From the book, Catholicism for Dummies by Trigilio and Brighenti

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