Does anyone know the clearance needed to build a fire pit in a wooden deck?

Question:I'm planning on building a 10x10 wooden deck on the hillside below my house. I want to construct a brick fire pit on the ground with the deck surrounding it. I cannot find anything on clearance needed, how high the walls need to be above the deck, distance from the decking to the brick. Fire bricks, if so how thick? Any help or directions on where to look for answers would be greatly appreciated!

Answers:
2 bricks thick should work [fire bricks ] depends on what you are burning.but never ever leave it unattended,until the fire is completely out.