SeaTac police yesterday began handing out the St. Patrick's Day version of the mood ring: small strips that revelers stick in their mouths for 10 seconds, which change color depending on how much alcohol is in their saliva.

Erin Go Ahhhh.

About 1,300 alcohol-test strips — which have been used by police departments in several states — are expected to be distributed by today at most SeaTac bars, hotels and casinos, said Police Chief Greg Dymerski.

"The whole goal is to raise the knowledge, the thought process, of drinking and driving," said Sgt. John Urquhart, King County Sheriff's spokesman.

Last year, 364 drivers were stopped in King County on St. Patrick's Day for suspicion of driving drunk, and 33 were arrested.

Given the problem, and that the strips cost the police department just $400, Dymerski said, they were worth a try.

Distributed by a Colorado Springs company that calls its product the Guardian Angel Personal Alcohol Test, the strips have been around for about six years, according to company CEO Amanda Beihl.

The directions for the alcohol test are a bit funny, especially when the idea is to use it in a bar: "Don't eat, smoke or drink anything for 10 minutes prior to test."

The strips are treated with an enzyme solution that makes the strips change color. If you're in pretty good shape, the strip will turn a creamy color; pinkish for a blood-alcohol level of around 0.04; grayish for around 0.08, the level for driving drunk.

The alcohol test has been distributed by police departments in several states, with mixed opinion.

In North Miami Beach, Fla., officers keep a few to pass out at bars, and, for instance, outside liquor stores when someone appears to be buying for a party. The department has tested the strips against alcohol breath tests and says they match up well.

In Wisconsin, though, the state patrol has come to see them as inaccurate, said Sue Hackworthy, chief of the patrol's chemical-test section. For starters, she said, a person who has been drinking might not follow the directions correctly. There is also a worry that a lower reading might embolden imbibers to believe they can take another drink.

Beihl said the tests are accurate for the moment they are taken. If someone has three beers, they will get a reading that might be higher or lower in the next half hour depending on how the alcohol is being absorbed.

Northstar Casino in SeaTac, with a sports bar that can accommodate more than 200 people and a nightclub that can serve more than 700, will start passing out the strips tonight. But the venue doesn't concentrate on celebration of things Irish. Fridays are known as "Hot Asian Nights" at Northstar, with shows that often feature Vietnamese entertainers.

Richard Olson, vice president of marketing, said the strips will be left out for customers as a novelty to take if they like but also will come in handy for staff to settle disagreements with those who think they should be able to order another drink.

A test kit may be offered, Olson said, with a polite but firm: "If you don't believe me, take a look."

Beth Kaiman: 206-464-2441 or bkaiman@seattletimes.com.