Welding tubing safely

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Very new welder here, using a MIG welder to weld structural steel tubing. Do I need to drill a hole (or leave one) when welding tubing shut as I join pieces? In other words, as I weld a piece of say, square tubing to another and then close it off with one on the other end, do I need to leave a way for hot air to escape?Roy BurmeisterMillermatic 211PRM Horizontal bandsawComplete Wood shop
Reply:I don't think so if the volumn is large enough to compress the hot gas. If your volumn is small and blowing out, you could stop right before the end, wait a couple of minutes for the air to start contracting and hit it hard to close the joint.Tig is a slow process and may require the use of vent holes. Or as we do stop short of the closure, wait,  and pop it closed.Weld like a "WELDOR", not a wel-"DERR" MillerDynasty700DX,Dynasty350DX4ea,Dynasty200DX,Li  ncolnSW200-2ea.,MillerMatic350P,MillerMatic200w/spoolgun,MKCobraMig260,Lincoln SP-170T,PlasmaCam/Hypertherm1250,HFProTig2ea,MigMax1ea.
Reply:The last headache rack (window protector) I made, I closed it up with no thought to pressure blowing out the end of the welds.  It was mig as well.  As shovelon said - had enough volume that it didn't make enough pressure.Dave J.Dave J.Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~ Syncro 350Invertec v250-sThermal Arc 161 and 300MM210DialarcTried being normal once, didn't take....I think it was a Tuesday.
Reply:The only time I have ever had this issue was TIG welding 1"x1" aluminum tube. A cool wet rag wrapped around the tube away from the weld area solved the problem. If you cant fix it with a hammer, it must be an electrical problem."Boy, everyone starts with a full bag of luck and an empty bag of experience. The trick is to fill the bag of experience before the bag of luck is empty."-Grandad circa 1990ish