I mean it's observable, we can observe the practices, we don't need to know more.@Nick_Radov That's very patronising... What do you know about the training of Italian Fire Brigade?
We use to treat infections with mercury, doesn't mean we should still do it.Although you may personally not imagine diving 50 m with air, this was not unusual - to not say absolutely common - for a long time for trained divers (at least in Europe...). (I won't go into the details how deep and how long i use to dive when my hair was less grey... that would be showing off...)