Questions about BACtrack S80 Pro

The recommendation is to calibrate either after 300 times (there is a counter on the screen) or annually, whichever comes first.

All electronic blood alcohol measurement devices unfortunately need periodic calibration to give accurate measurements. The cost and time involved I unfortunately do not know exactly. In my own experience, I compared an old device that theoretically needed calibration (4 years old) with a new one and the measurements were not particularly different. That's why, in my case, I don't do the calibration because I'm interested in the blood alcohol reading being 0 so that I can get behind the wheel, which means that even in the event of an incorrect measurement, I'd most likely be up to standard.