Accidental exposure to high concentrations of inert gas results in annual deaths from asphyxiation due to accidental exposure. And, "Hazards with inert gases and the risks of asphyxiation are well established. (Wikipedia)
It says that one danger is that a person does not sense the lack of oxygen. Yet this study showed rats to be "aversive" to argon exposure.
Are some inert gases considered safer than others? Maybe some are more noticeable, giving more warning. I'm sure industry would at least have some figures like ratios between deaths and accidental exposure?
Another study, Comparison of carbon dioxide, argon, and nitrogen for inducing unconsciousness or euthanasia of rats. shows decreased heart rate for CO2 compared to the others, which surprisingly contradicts what I find about the hypocapnic alarm response being triggered "mostly by carbon dioxide levels rising"