Fire Proof - For this achievement, you must make it through the forest fire area without getting set on fire in the last chapter of the game 'The Arrival'. My advise is to just keep trying to find open spots in the fire as your going up the hill toward the radio tower. You'll know if you've been caught on fire if the edges on your screen have turned red.
And if you do get caught on fire just let the Slender Man kill you and restart checkpoint. THE ACHIEVEMENT WILL UNLOCK AFTER YOU COMPLETE THE LEVEL.