None — A growing number of bars in Charlotte have "do-it-yourself" devices to test blood alcohol levels.
Some law enforcement officers worry the machines send mixed signals to potential drunken drivers, so Eyewitness News reporter Alan Cavanna put them to the test.
The machines have the look and appeal of a video game, but they're Breathalyzers, claiming to measure your blood alcohol content before you leave the bar. Nearly 20 area bars have the machines.
Two volunteers, Larken and Brittney, helped Eyewitness News with the test. Bartenders measured and Eyewitness News kept track of how much alcohol each consumed.
Both volunteers chose mixed drinks.
"I'm feeling pretty good," Larken said after two drinks. "I can definitely feel I've had something to drink, but I don't feel impaired at all."
"Two drinks in, I definitely feel it," Brittney said. "I don't think I would be able to drive home right now."
Both Larken and Brittney had one more drink each, which was their third in just more than an hour.
Once they finished, they followed the bar Breathalyzer's instructions and waited 10 minutes. Then, it was test time.
Larken paid the $1, put the straw in place and blew into the machine. It came back as 0.09 percent, which is over the legal limit for driving.
"I can definitely tell I've been drinking," Larken said. "I've got a little buzz, but I didn't think I'd be over the legal limit."
Next was Brittney, who admitted to feeling the effects of alcohol earlier. Her result was 0.12 percent.
"I would say this validates what I felt, and that would be tipsy," Brittney said.
Eyewitness News took the test one step further. Outside waiting were both a sheriff's deputy and state trooper.
Trooper E.P. Bradley tested their eyes, going up and down and left and right with a pen. Bradley said there were signs of impairment.
Then, nearly 35 minutes after their last drink, the deputy used his own Breathalyzer. Larken blew 0.04 percent, and Brittney also registered under the legal limit with 0.06 percent.
Bradley said it's impossible to explain why the results differed from inside the bar, but he did say that difference should lead everyone to take caution.
He worried about bar-goers not following directions or using the results of the bar Breathalyzer as a sure sign they're OK to drive.
"In my opinion, it gives somebody a false sense of security," he said.
Bradley said anything that makes someone think twice about drunken driving is a good thing, especially if they're near the legal limit.
"But if they're blowing anything that's higher, then call somebody, a sober driver," he said.
Channel 9 called the manufacturer of the machines in New York. The owner stood by their accuracy and said each vendor is taught how to maintain the machines every two to three months. But he stressed they should only be used as a novelty.
WSOC