incense
Well, no, Bill, not exactly. It is believed that the early Christians, in Rome at least, used incense because the Catacombs were actually the municipal cemetery, so they needed some "air conditioning". More to the point, however, was that they inherited the use of incense from the Jews (most of the early Christians were Jews), who used incense in the sacrifices carried out at the Temple in Jerusalem. If you read the regulations for these sacrifices in the book of Leviticus, you will get some idea of why they needed clouds of incense -- the smell must have been horrendous, and not like a barbecue, either. To say nothing of the flies. Speaking of that, there used to be a part of the Catholic liturgical garments called the "maniple", which was a narrow band of cloth, in the same color and material as the chasuble and stole, which was attached to the priest's left wrist. It's original use was to shoo the flies away during the celebration of Mass so they would not contaminate the communion bread and wine.

You mentioned the smells of people in crowds. It used to be the custom, and may be still, in English courtrooms to have a bouquet or nosegay, which the judge carried in and placed on his desk in front of him, also in some municipal processions, some officials carried a nosegay. The original reason was, as you note, the smell of the crowds (or, in the case of the courtroom, the smell of a prisoner brought up from the gaol or dungeon). These nosegays originally contained as much fragrant herbs as flowers, as it was believed that the aroma of the herbs could help overcome the dangerous humours.