So if my last drink was midnight on saturday and I calculate that my bac was about .15 it would take approximately 10 hrs for bac to return to 0 which would be about 10 a.m. On sunday morning. So it would be 10 a.m. Sunday when the 80 hour clock would start and if I did not take the etg test until 6:30 p.m. Thursday night that would be approximately 104 hours between bac of 0 and the etg test. It would seem then that etg would be under the minimum detectable range.