I do not advocate drunk driving
Let me be clear on my position. I’m just sharing what one heavy drinker picked up from another heavy drinker in a bar before they both drove home. I do believe one of the guys was a high ranking law enforcement officer who knew whereof he spoke.
When people are given the tube to blow onto , they put their lips around it, as instructed, and blow through their mouths. It never occurs to people to place their lips round the tube, as instructed, and then blow through their noses. A small amount of air will still go into the tube but not enough to “blow numbers.” This is an example of how people can learn things in prison that enhance criminality