Do key chain alcohol detectors actually work?

BOISE, Idaho (KBOI) - Pocket Breathalyzers are popping up in stores across the Treasure Valley, claiming to provide accurate readings of how drunk you are. Some people even use them to decide if they should get behind the wheel, so KBOI 2News put the $25 gadgets to the test.

BACtrack's Keychain Alcohol Detector is the device we picked up at Costco. As the name implies, it fits on a key chain so that you can take it with you for a night on the town. The Nampa Police Department uses an Intoxilyzer to test potentially drunk drivers at the station.

Two volunteers drink alcohol and provide their breath for our test. Mike Larkin, a commercial copywriter, is having whiskey, and college student Tess Wagner chooses mimosas, a mix of champagne and orange juice.

"If you have to rely on driving if your keychain says it's OK, I don't know if you should be driving as it is," Wagner said as KBOI 2News drove the testers to Nampa PD. Sgt. Tim Randall, who has read the instructions for the BACtrack device, holds the keychain and instructs our volunteers during the tests even though users can conduct their own tests. Randall administers ours for the sake of accuracy and consistency.

After our volunteers have had two drinks, Wagner registers a blood alcohol concentration of .02 on the keychain and .018 on the police unit. Larkin also blows a .02 on the keychain, but the Intoxilyzer detects no alcohol (.000).

Trooper Kenny Walker, who's on the Idaho State Police DUI Strike Team, says he wouldn't put a lot of stock in keychain alcohol detectors.

"There's no performance verification," Walker said. "There's no standards they need to adhere to. They may be close when they left the factory, but there's a lot of different things that come into play to keep the instruments working properly, none of which are used on these Breathalyzer key ring things that are being sold."

For our second and final reading, Wagner and Larkin knock back three more standard drinks at the Nampa Police Department.

Both devices instruct users to wait at least 15 to 20 minutes after the final sip because residual alcohol in the mouth can cause false readings. Half an hour after Wagner polishes off her measuring-cup mimosa, the keychain indicates she's now well over the legal limit with a BAC of .12, but on the Intoxilyzer that police use, she gets a .073, which is under the legal limit of .08.

Now that they've both had a total of five drinks, Larkin blows into both units for a .13 on the keychain and .075 on the police unit.

From these results, we find BACtrack's Keychain Alcohol Detector is much less accurate after our volunteers have had more to drink, with wide gaps in the numbers from the two devices.

A look at the manual shows accuracy was established at a blood alcohol concentration of .032 but not at higher levels. That number is not even half the legal limit of .08, meaning if you've had more than a few drinks, relying on the pocket Breathalyzer could be a crapshoot. The manufacturer stands by the accuracy of its device.

"I assure you, we have tested the unit at multiple BAC ranges to ensure the best accuracy and consistency possible for the technology employed within," BACtrack said in an email statement.

"You know, I'd say given the test results today, I'd be very cautious," Randall said. "There seemed to be quite a bit of disparity in those readings." Police say the best advice is if you feel a buzz at all, call a friend or a cab regardless of what number pops up on a keychain.