Well, argon is a "Totally" inert gas, I mean, is not toxic, or something like that, but it has a risk, is heavier than oxigen so in poorly ventilated areas it piles up and can cause death by asfixia. For the fumes, you can use a gas mask under the welding helmet

I've worked a little on gas industry, and I can tell you that cilinders have a serial number and normally a company can tell where is one of their bottles. Other think is that they don't want to search it. The refill of the bottles usually has troubles in very hot days, because the gas is hot, and g...