These groups are great thank you all for all the information I've received so far.
I am having a bit of trouble cramming some vents into a tight space for my heater and I'm wondering if it is ever okay to use flex tube that will be covered by drywall? Also is six inch round tube okay for running a vent to a home's second level from the basement. (about an 8 foot ceiling on the main level and about 2 feet to the ceiling in the basement from the top of the furnace).
Also my stove will not be on an outside wall and I'm wondering about venting an over the range hood either down and out the basement or 90 degrees out a side wall with about a six foot run and then out. Could this just be some nice stainless pipe that might look cool and modern or would it have to be built in?
Thanks for any information.