To my knowledge, you could use Stainless steel or PVC venting (Type "BH")
In Canada, it's certified to CSA 636 for use in venting. As for keeping the exhaust (Products of combustion) from coming through the drain, a trap is used. This way, the water seal in the trap will not allow the carbon dioxide in the products of combustion to enter the living space.
Check the owners' manual to make sure the unit will allow the length of vent you are proposing.
Hope this helps!