I'm a welder by trade, the shell is only tacked and easy for me to get back inside it someday plus the burner isn't even welded to it. I'm using a T-fitting for my mixer and once I have it together, I'll attach a picture. My air/fuel supply will be made of 2" sanitary Stainless tubing, stuff left over from a job. Here's a couple pictures so far, I'll still in the process of covering the exposed insulation