ticketed welder here, currently weld to mil spec on government vehicles. When tig welding you should not have to go over 20cfm or you start risking turbulence in the gas flow which can cause air to mix with the shielding gas. I always run gas lenses when i tig and this lets you run lower cfm because of the smooth even column of gas it creats compared to running a standard collet setup. I run 12 cfm on anything tigged indoors unless welding reactive metals than i trun it up to 15-18 with a huge gas cup backup gas and a following purge cup.