Your Own Personal Breathalyzer

Are you OK to drive, or should you call a cab?

If you make the wrong decision, you may end up in jail or worse. You will meet lawyers. You will wear out your checkbook. And you will flinch when the car insurance bill comes.

Or you could buy your own personal breathalyzer and blow.

Devices cost $3 to $300, and their accuracy varies almost as much. The wrong device is worse than useless if it puts a drunk behind the wheel.

Yet more and more people are slipping one into their glove compartments. According to Wintergreen Research, sales of breathalyzers hit $284.6 million in 2011, and they forecast that number will climb to $3.2 billion by 2018 as prices fall and accuracy improves. In fact, French law already requires that all drivers carry one.

A guide, not a guarantee

In the end, the only number that counts is the one on the police officer's device.

A first-time DUI can cost thousands in court fees and will easily double your rates, says Penny Gusner, consumer analyst with CarInsurance.com. A second DUI may send your rates up 300 percent -- when you get your license back. (See "Calculate your limit: Avoid a DUI disaster.")

A final caveat: Blowing a number under the legal limit is not a free pass to drive. Impairment is more than just a breathalyzer number, and it is possible to be under the legal limit and still be arrested.

According to Gusner, the insurance premium jump for impaired driving is going to be very similar to a DUI conviction.

"I would give myself a wide, wide margin of error," Gusner says.

A long way from the Drunkometer

While alcohol intoxication is defined as a blood alcohol concentration (BAC), testing blood is just not feasible when you are out on the town.

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