Michael, the archangel, means "who is God," or "who is like God." He is the warrior angel and defeated Lucifer, and banished him from the Gates of Heaven. His prayers are commonly used throughout investigations for protection.
Upon entering an investigation, or if you need protection:
"Saint Michael the Archangel, defend us in battle. Be our protector against the wickedness and snares of the Devil. May God rebuke him, we humbly pray, and do thou O'Prince of the Heavenly Host. By the power of God, thrust into Hell Satan and all Evil Spirits who wander through the world for the ruin of souls. Amen."
Upon leaving:
"In the name of Christ, I command all human spirits to be bound to the confines of this place. I command all wandering spirits to go where Jesus Christ tells you to go, for it is he who commands you. Amen."