Yes, you're welding. No medical talk, and no medical tank terminology (welding tanks are designated by cubic feet, not terms like "M" "H" or "E" as medical tanks are). If you feel uncomfortable in case you are asked "Welding what?" you could have a story something like the one I have ready, which is that I know nothing about welding; my brother-in-law is coming into town to help my daughter and her husband, and this is what he told me to get. I haven't had to use that -- usually, they're not going to ask. You'll want a regulator also, of course, but don't buy it from the welding supply store: this one is good, and there might be a Harbor Freight store near you: http://www.harborfreight.com/catalogsearch/result?q=oxygen+regulator This will fit on any size welding tank. If you have Amazon Prime, you can get this one delivered quick: https://www.amazon.com/BETOOLL-HW9005-Welding-Regulator-Cutting/dp/B01IJI04XW/ref=sr_1_1?s=industrial&ie=UTF8&qid=1478042088&sr=1-1-spons&keywords=welding+oxygen+regulator&psc=1 For a mask, you can start with this (also Amazon Prime): https://www.amazon.com/Medsource-Adult-Non-Rebreather-Oxygen-Mask/dp/B00BBFQ64M/ref=sr_1_1_s_it?s=hpc&ie=UTF8&qid=1478042243&sr=1-1&keywords=non-rebreather+oxygen+mask
You probably also want either a rolling stand, which is good for handling the tanks, or a stationary stand. You can get that at the welding supply place. You might want one larger tank (I think they get kind of unwieldy above 80 cu ft, and you will have to bring it back to get it refilled/replaced) and also a smaller one to have in your car.