"How dry I am, how wet I'll be, if I don't find the bathroom key."

NOT SO very long ago, the urge to go was the first clue that we'd had too much to drink at a bar, party or concert. Other telltale signs? The inability to walk a straight line or finish a thought. And irrepressible laughter when watching an Adam Sandler movie.

Then there were the really glum signals - being arrested for DUI or, by far the worst, getting into an accident. That could leave you with a lifetime of regret, expensive legal fees, a suspended license or even jail time.

But today there's a safer, scientific and even fun way to monitor inebriation, thanks to personal-breathalyzer pioneer Keith Nothacker, the Berwyn (then Devon) native and Penn grad behind the industry-leading BACtrack brand.

How helpful are these gizmos? Current BACtracks claim a level of scientific accuracy close to the professional-grade, $10,000 breathalyzers found in police stations. Yet BACtracks can be small enough to dangle on a keychain and cost about the same ($29.99 for a BACtrack Go) as a good case of beer or bottle of Scotch.

Gizmo Guy's even more taken with Nothacker's Bluetooth connected Vio and Mobile models ($49.99-$100 at Amazon, Costco, Best Buy, Pep Boys, AutoZone and more) that feed enhanced information and guidance to a smartphone (Android, iOS) and, soon, the Apple Watch.

Don't be sucker-punched by cheap knockoffs, also spotted on Amazon, which cost just a few bucks and are uniformly panned. More reliable are single-use testers with color-changing crystals ($2.50 at breathalyzers.com).

HAPPIER HOLIDAYS: There's no excuse not to carry a good tester when you're barhopping, say, on St. Patrick's Day today. Or April 25 during the day-into-night Center City Jazz Festival. And why not tuck one in your pocket for picnicking long and hard on Memorial Day, or partying at one of the summer's many outdoor music festivals?

"Would you drive a car that doesn't have a speedometer?" pondered Nothacker. "That's the level of disadvantage we all used to have, that first got me thinking and working on this product as a student at Penn [circa 2001]. Today, our sales aren't seasonal, they're year-round. Truthfully, there isn't a day when you shouldn't be drinking and acting responsibly."

A-B-Z's: Taking a reading of your drunken state is easier than whistling. All you have to do (borrowing Lauren Bacall's famous line from "To Have and Have Not") is "just put your lips together and blow."

Actually, you first breathe in, then out into a plastic-tipped (replaceable) mouthpiece as cued by a beep and, on connected models, with a clock-style display on an app-loaded smartphone.

Internal circuitry takes a measure of your "deep lung" air to calculate the level of alcohol absorbed into your bloodstream.

Although penalties differ in various jurisdictions for lower levels of intoxication, it's pretty certain that a measured blood alcohol content (BAC) of 0.08 - that's 8/100ths of 1 percent alcohol in the bloodstream - will get you locked up.

DO'S & DON'TS: Always ready to take one for the team, Gizmo Guy dutifully drank a whole lot of red wine (rated 12 percent alcohol) one night with two BACtracks at the ready to calculate my state of being.

Then, a couple of nights ago, I let a friend mix up and serve me a couple of Cosmopolitan cocktails.

Being on the smaller size (5 feet 8, 140 pounds), I'm a cheap drunk. After the first 4-ounce glass of Cab, both models rated my BAC at 0.026.

The Mobile's connected app suggested that I was "slightly intoxicated" and predicted (a nice touch) that it would take about 90 minutes for me to sober up, if I drank no more.

After downing 12 ounces of wine (half a bottle) over a two-hour span, the BACtrack Go calculated my blood-alcohol level at .05 while the Mobile rated me at 0.043 percent, halfway to the hoosegow.

Bigger surprise - two tastes-like-candy Cosmos also elevated my BAC to 0.04.

BOOZERS BEWARE: You should not administer a breathalyzer test (nor should police) until at least 15 minutes after your last consumption of drink or food. It takes that long for the alcohol to get out of your mouth, into your bloodstream.

When I immediately "blew" after gulping, the BACtrack Mobile incorrectly rated my BAC at 0.18 and treated me sternly, assessing: "Your eyes may be glassy. Your face may be flush and the odor of alcohol permeates your body. Your motor skills are impaired to a degree that coordination may be lost.

"Sustaining a train of thought for more than a few seconds proves extremely difficult. Feelings of nausea and physical uneasiness increase. Driving at this level BAC increases your chances of getting in a fatal car crash 25 fold."

Said Nothacker: "Our goal with the app is to explain things in scientifically accurate but calm and relatable terms. Ideally, using a breathalyzer will help you have fun and still be responsible."

How about cure-alls like cold showers, coffee or a Listerine gargle?

"BACtracks show they're old wives' tales," Nothacker said. "A gulp of Listerine puts extra alcohol in your mouth. A cold dunk might clear your head but doesn't reduce the BAC. The only good thing with coffee is that the drinking period gives you extra time to sober up."

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