Institutio generalis Missalis Romani

The priest, having put incense into the thurible, blesses it with the sign of the Cross, without saying anything. Before and after an incensation, a profound bow is made to the person or object that is incensed, except for the incensation of the altar and the offerings for the Sacrifice of the Mass. The following are incensed with three swings of the thurible: the Most Blessed Sacrament, a relic of the Holy Cross and images of the Lord exposed for public veneration, the offerings for the sacrifice of the Mass, the altar cross, the Book of the Gospels, the Paschal Candle, the priest, and the people. The following are incensed with two swings of the thurible: relics and images of the Saints exposed for public veneration, which should be done, however, only at the beginning of the celebration, after the incensation of the altar. The altar is incensed with single swings of the thurible in this way: If the altar is freestanding with respect to the wall, the priest incenses walking around it; If the altar is not freestanding, the priest incenses it while walking first to the righthand side, then to the left. The cross, if situated on or near the altar, is incensed by the priest before he incenses the altar; otherwise, he incenses it when he passes in front of it. The priest incenses the offerings with three swings of the thurible or by making the sign of the cross over the offerings with the thurible before going on to incense the cross and the altar.