Why does an LP gas fire pit need these items? LP gas needs to mix with air to create a cleaner more efficient burning flame. This reduces the amount of black soot buildup on any media in your fire pit. A burner pan creates a barrier between your media and the air mixer. You never want to bury the air mixer under any type of media, always place it underneath the pan.
We always recommend consulting a professional if you are ever unsure of whether or not you are correctly assembling your gas fire pit.