I assume you're joking, Either way. One morning when I took the bus to work the bus driver had repeated problems getting the bus to start due to the breathalyser. I heard him complain to the passenger behind him, about it malfunctioning. The passenger volunteered to test this theory, by also blowing into the device. The driver handed him the hose, the passenger gave it a go, the bus started, and the driver shrugged his shoulders, and off we went, only slightly delayed.
Dunno where the parent comment was referring to, but different countries have different standards. In Colombia the bus transit stations all have breathalyzer stations and the drivers have to pass the breathalyzer before starting their shifts. It was pretty wild to see as an outsider but completely unremarkable to everyone else.
I'm not sure if this is preventable.