Very roughly, after stopping drinking you go down 10 mg of alcohol per 100 ml blood per hour.

How long does it take to actually get rid of any trace of alcohol in one's system?

The alcohol lever never will be nil in healthy persons. Alcohol in very small doses is in bread, in fruits, in fruit juices, in kefir and so on. Ripe bananas always have a tiny bit of alcohol in them. You just can't eat enough to get noticeably pissed.

There always has to be a lower limit under which a person has to be considered sober. 'No trace' is not a sensible idea in a time in which ultra small traces can be found.

Wolfgang