Drinking probably wouldn't be half as deadly as it is if it wasn't for driving.

For less than half of the price of a DUI, you can find a battery-powered alcohol breath-tester. This year, a few days before my birthday party, I bought a breathalyzer. 

With this one gadget, and a little legwork,  I would be able to tell if people were having a good time at the party!

This AlcoHAWK model featured a red three-digit display, which, if operated properly, would indicate precisely when it was time to call a taxi-cab (.08) and when it was time to start hitting on Joan Rivers (.26).

It was lightweight, easy to use, and it only required one 9-volt battery, which was quickly obtained from our smoke alarm.

Once again, it was time to gather a bunch of scientists around a keg. 

Nick was the first to arrive, and he set about checking the beer temperature.

I steeled my nerve for a long evening. I swore I would drink until I learned something. 

A breathalyzer works by measuring the air in your lungs.

Because your lungs are where your blood meets the air.

In thousands of little sacks at the end of a thousand little branches, a little gas exchange takes place. With each breath, some of your blood cells exchange their carbon dioxide (CO2) for oxygen (O2). Your blood will also accept other things that are in your breath, such as carbon monoxide and nicotine from cigarette smoke, cocaine you have snorted, or Beclomethasone from your asthma inhaler.

Those blood cells also get rid of chemicals into your breath, such as ketone bodies and alcohol.

If you measure the amount of alcohol in your breath, (BrAC) and multiply it by about 2,400, you will have calculated the amount of alcohol in your blood (BAC).

The breathalyzer instructions warned that it was important to wait 10 minutes after a drink if we wanted an accurate measurement. This was because a little booze tends to remain in your mouth when you have been drinking which can greatly increase the alcohol percentage measured from the air in your lungs.

Of course, at a party, asking people to stop drinking for 10 minutes is a little like stopping the music and turning on all the lights. I decided to just do the best we could.

Subjected to first test of the night was Meaghan. She had downed two "chocolate cakes", which are baked from vodka and Frangelico (hazelnut liqueur). Her breath revealed a .05 BAC.

Damon was next to try out the bar room electronics. He had come from dinner at a Mexican restaurant, where he had drank two margaritas on the rocks. He had also finished two beers at the party. He blew a .06.

I was surprised. I thought Damon's BAC would be much higher after four drinks. Maybe the restaurant margaritas were watered down, or the food had slowed the liquor's path into his bloodstream.

When you are hosting a party, and guests start arriving, you can simply be too busy to get much drinking done. Despite my best efforts, It took almost an hour to finish my first red plastic cup of keg beer.  When I was done, I blew a .03.

Justin had two shots of Jager ten minutes before the breathalyzer. He was tested at .04.

Stephanie had just finished half of her glass of red wine "a few seconds ago" when she took her first breathalyzer. This  resulted in the highest score so far in the evening, a .19! Presumably, the alcohol in her mouth had caused the breathalyzer to bump up her reading.

Meaghan was back for a second test after drinking a third Chocolate Cake plus a Jager & Red Bull. Her BAC was now past the legal limit for driving, .12.

by 10:30, Nick had also consumed two Chocolate Cakes, with two beers and two sips of wine. His BAC was also past the legal limit for driving, at .17.

Carrie drank one beer over 40 minutes, and tested her BAC. Carrie was actually one of the few people who would actually need to drive themselves home. Her BAC barely registered, a .01. That didn't seem right to us, so we tried it again and got the same result.

Justin hadn't added to his blood alcohol, he had still only had 2 shots, and sure enough, his BAC had fallen. He was down to just .02.

Stephanie had been at the party for the same amount of time, and had drank only one glass of wine, but BAC was registering a .04. Stephanie started to get a little annoyed that Justin could apparently drink whatever he wanted, with very little effect on his blood alcohol level.