It's not often that you need to get drunk for a story.

But hey, how else are you going to test one of the personal breathalyzers that are part of a growing $20 million industry?

Over the past two years, several handheld devices have been introduced to the market and are being used as screening tools by parents to test their kids, employers to check workers using heavy equipment, high school personnel to test students at proms, football games and other functions, and by regular consumers to monitor their drinking.

They're designed to measure the concentration of alcohol in the human breath, which indicates how much is in the bloodstream. Prices range from $10 for small keychain models to $250, although accuracy varies widely. Results are not admissible in court.

Most consumer models use a semiconductor sensor to detect alcohol, which is less sophisticated technology than what is used in professional devices used by police.

The personal breathalyzers, like the $79.99 BACtrack B70 by KHN Solutions Inc. of San Francisco that I tested, are more practical as screening devices. To get an accurate reading you need to wait 20 minutes after drinking, eating or smoking before blowing into the device. And the manual emphasizes that users not use the BACtrack as a tool to determine whether you should operate a motor vehicle or equipment or perform any other dangerous act.

"What we want to do is educate people and have a product to estimate alcohol level," said KHN founder Keith Nothacker. "Just putting a number on what was a feeling, we think, is very helpful and very educational."

People who use this device will see a big difference, for example, in their alcohol level if they drink while eating or on an empty stomach. With two glasses of wine without food, I registered .10 (.08 is legally drunk). On another occasion after I drank 2 1/2 glasses of wine over a long dinner, I registered .03.

Blowing into the device before the 20-minute wait may show a wildly high reading, but having any reading of alcohol would be of value to those using the breathalyzer as a screening tool.

"Parents use this to test underage minors," he said. "If my mom had had this when I was a kid I would have been in a lot of trouble. It's a great excuse for kids not to drink at a party."

It's also used by recovering alcoholics, homeless shelters and sometimes by divorced parents in cases where alcohol use was an issue. "The divorced husband or wife may not hand off the kids unless the ex-spouse agrees to take a breathalyzer test."

The BACtrack, for one, is a slick device about the size of a cell phone.

Operated by AA batteries, it gives you a 10-second countdown and then you provide a deep 5-second blow through the breath chamber. The device analyzes the breath for 3 seconds and then displays a digital result on the screen.

You mouth does not touch the device, so it could be used by more than one person at a time.

It took a little practice to deliver the right kind of breath. If you don't blow properly, the screen gives you an error notification.

The batteries last for 300 uses, and like many other personal breathalyzers, it may need to be recalibrated every six to 12 months.

BACtrack, which was featured in a "CSI Miami" episode and recent Discovery Channel "MythBusters" show, is sold at Target.com, Amazon.com and other Web sites, which also carry myriad other brands and models of breathalyzers.