Here is a collection of tools I use for purging air from behind welds while welding stainless steel.

The screen mesh you see on the long purge troughs is a sintered stainless steel mesh, that is normally used for chemical filters. Welding it to the edges of the sheet metal troughs is a very tricky bit of welding. It provides a very even coverage of argon behind the welds. The troughs are usually adhered to the backs of the welds using aluminum foil tape.

The connectors I use are designed to grab 1/4" OD hose. You simply push the hose into the connector. To remove the hose you push in on the retaining ring while pulling the hose out, otherwise it is quite secure.

I used the small valve clusters to route gas to multiple purge jets if needed.

The directional jets are just large diameter gas lenses with hose connectors on the backs.

The large space-age looking things are called Tube-a-liners.

They were made by Dearman for use in orbital TIG welding. I picked mine up on eBay for very cheap. There is also a picture showing one being expanded with 20 psi air pressure. They are designed to expand inside a pipe joint to be welded. The 2 halves of the tube-a-liner can expand independently in case the pipe pieces have different wall thicknesses. They have enough expansion power to clamp and align the pieces to each other. The orange rubber washers seal on either side of the joint. The smaller metal tube is the feed for the argon shielding gas that floods the inside of the weld joint.

Very slick widgets.

The rubber stoppers are for pipe and tube purges where you just want to purge the whole pipe.

The pie-tin is actually a device I rigged up to purge the seam inside a brewing tank when you are welding on a fitting. The pie-tin is flexible enough to take the inside curve of the tank when pressed against it. The smaller cone is threaded onto the central tube so it seals the opening in the fitting. The gas is fed into the end of the threaded tube. Back-purging is one of those things that keeps breeding new widgets. The companies that make them charge a lot, so most people end up making their own.