It's a very simple Roman-Catholic prayer. I tested it and it's quite good for cleansing and protecting the place. It is usually said at night, before bed. It has a very calming and comforting effect.
Visita, quaesumus, Domine, habitationem istam, et omnes insidias inimici ab ea longe repelle: Angeli tui sancti habitent in ea, qui nos in pace custodiant; et benedictio tua sit super nos semper. Per Christum Dominum nostrum. Amen.
Visit, we beg Thee, O Lord, this dwelling, and drive from it all the snares of the enemy; let Thy holy Angels dwell herein to keep us in peace; and let Thy blessing be always upon us. Through Christ our Lord. Amen.
I also found that angels start walking around the room after a few repetitions of this prayer. I like to repeat prayers at least 3 or more times in a row, in order to get more power out of them.
I'm assuming most of the practitioners here know how to speak Latin, but here's a pronunciation guide anyway: