If your gonna do it, Argon is the only gas to use really. Welding supply shops. A small tank should last you a year. Remember it is only for short term use. These days I mostly use it to back fill a carboy while I am waiting for it to clear (week or so at most). I use a solid stopper in the carboy which has dangers if the temps are rising in your winery. I also use it each week on my bottle of top up wines. Fill the barrel (top up) and then backfill the open bottle with Argon and then stopper it until the next week. This will keep your top off wine from oxidizing as you empty it (slowly) week to week. When it gets down to half a bottle, transfer to split. Rinse repeat......