I had the training on LOX and high pressure oxygen, and even things like having shoes with polish on them can be flammable. We had a special dispensation not to polish our working shoes, because of the risk of the wax catching fire. In the military, where shoe polishing is considered an art, and your shoes are expected to be a mirror like gloss at all times, but us Instrument fitters were exempt. We did have fun with that rule.
But remember that oxygen, even at 1 atmosphere, is very much going to support combustion, even for things they you would not consider flammable, like paints, most plastics (including PTFE, even if half the oxygen equipment uses it for seals and piping), aluminium, once the oxide layer is breached, and even stainless steel. Put it under pressure and many more things will burn, such as that little burr scraped off the surface when putting the lid on, and definitely any cheap unknown seal material used in the lid, likely some form of silicone rubber or EPDM or nitrile rubber, it will likely either smoulder or simply burn, and once there is a hole through the gas flow will turn the burning material into a flame jet.
We had separate armoured rooms where the oxygen equipment was kept, with blast proof doors, and with clear access so that the blast would not damage much more than the room. Inside the lighting was all heavily armoured, liquid tight IP68 rated Pratley EEX rated boxes, lamp enclosures, and with the power switch outside the room. The filling of high pressure cylinders was an entirely separate section, with a prefab hut for the operation, so the blast would not be fatal for too many other than those inside, and the cylinders were always filled with no people in the room, and all outside by the vapouriser, behind it's own blast wall.
Pure oxidiser gases are dangerous. Oxygen, flourine, chlorine and bromine, because they all support vigorous combustion and are common, and either gas or liquid depending on temperature and pressure, and are a relatively common material to get in pure state. iodine is also dangerous, but is not as reactive, and the others in the 2 colums are either solid, or are simply going to kill you for other reasons.
That 304 stainless series thin wall pot is really only rated for air, or water, at no more than 4 bar, as it will want to turn to a ball, and being thin wall it likely is just about capable of handling 6 bar before splitting along the side, from all the cold work that has been done shaping it. 1000 cycles of pressure to 4 bar likely will see it failing.