Don't do this. Industrial argon isn't necessarily clean enough for food-grade purposes and may well contain unknown / poisonous substances. You should know better than to make hazardous recommendations.
Industrial argon is produced by fractional distillation of air and is a mostly inert gaz. Most of it is not food rated because it's mostly useless in food production. You are taking an extremely limited risk by using it to displace air in a wine bottle especially considering you are not actually puting it inside the wine.
Obviously you should use food rated argon if you want to be safe. It's just going to be more expensive and harder to source.
Yes, my understanding is that it would take a mistake in the process to introduce a toxin. The tanks are dedicated to argon over their lifetimes, though they do have a complicated chain of custody. For food-grade argon they do check for safety.
My sense is that I'd be better off avoiding all plastics (not feasible in this world) than waiting for food-grade argon. But yes, this is a decision each person should make.
> “If you want to be safe” doesn’t really jive with “extremely limited risk.”
Of course it does. To put it bluntly, it is extremely likely that any bottle of industrial argon is actually food safe because it's produced in basically the same condition that food safe argon. The main impurity while producing argon is oxygen. The main difference between industrial and food safe argon will be how their container is handled but argon as an environment is not really suited to bacterial development.
If you don't feel okay taking this risk, you can buy food grade argon which, well, is guaranteed to be food safe.
Also, don't get me wrong, I'm specifically talking about argon there. I would never use industrial distilled water or ethanol with food for example. That would be risky. I have heard of people using industrial CO2 to carbonate beverage. That makes me uneasy because CO2 is a good solvent.
