BACtrack Keychain Breathalyzer (Black) - Ultra-Portable Personal Alcohol Tester with Keyring | Perfect for Nightlife, Workplace Safety & Responsible Drinking

This is an update to my original review from over five years ago. My unit lasted for over 5.5 years before it would display only '0.0' during a test. Everything else worked so I assume the sensor finally wore out and/or it needed a factory calibration. (Note: BACtrack recommends periodic factory calibrations, but at $19.99/each it's simply not worth it for a $25 unit.) The BACtrack Keychain was definitely a cost-effective, reasonably-accurate solution for me at the time. But in the interest of greater accuracy and lifecycle costs, I decided to replace it with a more expensive, more accurate self-calibrating unit with a user-replaceable sensor. That said, I still give it a five star rating based on my overall five year experience.I first saw this device in a comparison test of breathalyzers in the April 2014 issue of 'Car and Driver' magazine. It tested as well as - in some cases better than - a unit costing 5x more. The device feels well-made for the price - not especially rugged but not cheap either. It operated as-described. It comes with a Duracell AAA battery as pictured. The instruction manual is clearly written and the table describing effects of increasing levels of alcohol was informative.I have no way of verifying the unit's accuracy but it seems to work properly, displaying roughly proportionate increases in BAC when consuming alcohol. After 15 hours with no alcohol it registered a BAC of 0.00. After one shot and a fifteen minute wait it indicated 0.03. After an additional 3/4 bottle of beer and fifteen minute wait I tested at 0.04.In the FAQs, when queried where the unit was made, BACTRack customer service responded, "We do all our design, testing, calibration and quality assurance here in California" but for whatever reason omitted that it is also "Assembled in China" as printed on the packaging.Overall I recommend this device: it feel adequately constructed for the price, seems to work as advertised. I can see it being fun at parties and could save your license!