If he touches you, you will be sent to the pocket dimension. If he is chasing you, there is no chance of outrunning him. Moves slowly and can phase through solid objects.
This is unless MTF guards capture it at the end of the game, but this is not something to rely on. SCP-173 will appear throughout the entire game randomly and cannot be contained. If line of sight is broken, SCP-173 will move with incredible speed towards the player, instantly killing them most of the time. As a result, this line of sight must never be broken. Looks like a peach statue with a face on it.
