I purchased an S80 a few years ago. Worked perfectly, just make sure you have it calibrated as per the manufacturer's recommendation. I waited too long & had to purchase another unit. Easy to use, very accurate. No one leaves a party until they're checked.
I've used this device and have been happy with reliability. Make sure not to use unless you wait until mouth alcohol is gone (15 minutes). Draw back, get calibrated after 100 uses. If you repeat use to quickly you can damage fuel cell and get false readings.
I just received the unit and it doesn't register at all. Always states "Out", even though we are blowing into it as directed. Changed the flow settings and breath time, but no difference. I'll see how they follow up and let you know how it goes. Very disappointed right now. Won't rate it since this unit doesn't work.