Stay up-to-date with our latest Solar Eclipse coverage

Do personal breathalyzers give you a false sense of security about your drinking?

MEMPHIS, Tenn. -- Beale Street is full of music, good times and plenty of alcohol, but do drinkers realize just how much they have put back?

"I had two beers. One at supper, one before supper and then I had a double down there," one Beale Street patron told us on a recent Friday night visit to Memphis' most famous street.

Personal breathalyzer tests are a quick way to find out if you have had too much. We found them at local drug stores, ready for instant purchase, took them to Beale Street and found some willing volunteers to test it out.

The device WREG's April Thompson was testing is said to be one of the most reliable on the market and it was pretty much ready out of the box. A few instructions, snap on one of the 3 interchangeable mouth pieces and you are ready to go.

"Just blow continuously until you hear the beep," we told the tester.

The first tester told us he wasn't drunk.

"How much have you had to drink?"

"Well you know..." he replied.

"Have you had several?"

"No one drink. One drink. So it probably won't even register," he said.

Remember anything 0.08 and above is considered over the limit to drive in Tennessee.

In just a few seconds we had his reading.

"That's point-one-nine."

Yep, he would be considered over the limit.

"Are you surprised by what it says?" asked Thompson.

"Yes I am."

"You didn't think you were that drunk?"

"No. I don't feel like it at least."

Our next tester said she knows her limit.

"How many drinks would you say you have had?"

"Today?"

"Well tonight. "

"When do you start tonight?" she laughed.

"So do you think you are drunk?"

"No. Not even close. Not even close."

Let the portable breathalyzer be the judge.

"There's the beep. It says point-oh-three," Thompson said.

Attorney Mark McDaniel tries hundreds of DUI cases that often involve breathalyzers and he said he has some concerns about these portable models.

"The risk is far outweighed by the benefit of someone taking a personal breathe test device and then chancing whether or not they are stopped. They are going to driving under the influence," he said.

Users may rely on the devices too much, he said and the readings won't hold up in court of law.

"I do think it will give them a false sense of security, especially in cases where the personal breath testing device might be just under the legal limit," MCDaniel said.

He also pointed out there are several things that could cause misreadings with the breathalyzers.

The instructions said you should not eat or drink alcohol 4 hours before testing.

"People don't understand that alcohol will generally peak in your system 45 minutes to a half hour after the last drink," said McDaniel.

That means a high alcohol reading may not show up immediately and there can still be operational issues.

Our next tester told us he had consumed plenty of drinks about an hour earlier.

"How many drinks have you had?" we asked.

"About 5 or 6."

"Five or six. So you pretty much are wasted?"

"Naw..but I am feeling it."

When he blew into the breathalyzer, the results were surprising.

"Then it said point oh-oh," we told him.

Whether it was our error or not, it's an error that can still happen with the self test.

"If the police give it to me and it reads zero-zero..I will trust it all day," the tester told us. "That's a risk you know."

"So you don't trust it?" we asked him.

"No. I ain't taking that risk."

Still, one thing all of those testers told us, they were not planning to drive after drinking anyway.

"I got a designated driver. I got two actually,"  one tester said.

"We got Uber. It's 2017. We got Uber, got a taxi, got friends, got family," another told us.

"I don't drink and drive ever. I plan ahead, get a ride. You can get hurt. I just don't do it," said another.

Whatever your party plans, being aware of your alcohol intake is always the best idea. Portable units may have a place, but they can't replace common sense.

"If you feel like you have had enough alcohol to question whether or not you should be driving an automobile, I think you have already answered your own question," said McDaniel.

Portable breathalyzers can range from a few dollars to hundreds of dollars.