Unlike urine drug testing, which vary in accuracy, reliability, can not determine when the drug was taken, or if the subject is currently under the influence, breathalyzers have become very sophisticated and accurate in determining current blood alcohol level. This has become a powerful law enforcement tool. In all 50 states the current legal limit for intoxication is .08% blood alcohol content (%BAC). Exceed that limit and you will invariably be charged with Driving Under the Influence (DUI).

When you drink alcohol, it enters your bloodstream through your digestive system. Your lungs are crammed with capillary blood vessels where they exchange carbon dioxide from your bloodstream (collected from cells throughout the body) for inhaled oxygen. The oxygen is then absorbed into the blood and carried to the body's cells. You exhale the carbon dioxide removed from your blood, and if your have been drinking it also contains alcohol found in the bloodstream. Breathalyzer technology is capable of determining your blood alcohol content by sampling the alcohol level in the air you exhale.

There are about 30 different brands of breathalyzers available today. They are even available for consumer purchase at some department stores, specialty shops, and on-line. Most of them work though infrared absorption, meaning that infrared light is passed through the exhaled breath, then a detector at the end of the beam of light determines how much of the light was absorbed by the air sample. Using this information, your blood alcohol content can then be determined by processing the measurement.

While most of us are familiar with the portable hand held devices carried by law enforcement officers, there are also desk models that have improved accuracy. Both use the infrared absorption method, and are commonly referred to as active testing - meaning that you have to actively blow into the device. The hand held test in the field is usually a preliminary test. If a subject fails the preliminary test, they are taken into custody and asked to repeat the test using the more accurate tester at the police station. A more accurate test is more likely to hold up in court should the subject go to trial.

While most of us are aware of active breathalyzers, many people are not aware of the use of passive testing. Passive testers are typically built in to the enforcement officer's flashlight. We all know the tendency of officers to stick their flashlight in your face, so you may be blood alcohol tested without even realizing it. There are a few tricks to overcoming a passive test.

First, discreetly roll down your window as soon as you realize you are going to be pulled over. This allows any built-up fumes in your car to escape before the officer arrives at your window. When the officer approaches the vehicle and shines the light in someone's face, the tendency for most people is to try to look past the flashlight and see the officer. Basically they are breathing right into the flashlight. This allows the officer to get a good reading using directly exhaled breath. To avoid passive detection, do not look at the flashlight or the officer. Look straight ahead. Breathe very infrequently and shallowly while the officer shines the flashlight in your face. In fact, it is best if you can actually hold your breath while the light is shining in your face.

If officers do not get a reading on the passive tester, they may let you go or simply write a ticket for whatever infraction they stopped you for. If they get a positive reading with the passive tester, they will ask you to step out of the vehicle and seek to administer an active test without ever revealing they used a passive test.

As already described, if you fail the active hand held test they will take you into custody and then administer another test using the more accurate desk model at the police station. Desk top testers require you to blow fairly hard in order to get a reading. This works against you, as the deeper the air expelled from the lungs the higher the reading. The reliability and accuracy of desk model results are hard to dispute in court.

Since breathalyzers are accepted as reliable and accurate, there is really no way to fool them. The best bet to pass a breathalyzer is time - allowing your body to process the alcohol and lower the blood alcohol content. Most states allow you at least an hour to decide whether you want to take a breathalyzer test or refuse it. Your strategy should you become a DUI suspect is to initially refuse to take the field breathalyzer test. If you are taken into custody, in order to stall for time tell the officer you want to contact your attorney before deciding whether to take the test. Pretend to call your attorney, or actually call an attorney if you have one, or look up one in the phone book if possible (preferably one that specialized in DUI cases). Then follow their advice. During this time, ask for water and drink as much as possible, first rinsing your mouth thoroughly. Go to the bathroom several times. Stall as long as possible.

When you can not stall the officers any further and they demand you take the test or officially refuse it, you have a decision to make. In most states, refusing a breathalyzer means mandatory punishment like a six month suspension of your driver's license, but you may escape a DUI charge and conviction. On the other hand, if you have stalled for an hour or more, your blood alcohol content may have dropped below the legal limit. You want to consider how much alcohol you consumed in general and how much you consumed in the hour or so before being detained. Did you do several shots right before you left the bar? Your alcohol content may still be rising. If you were slowing sipping on a few beers over the course of the evening, then your blood alcohol may have gone down significantly during the past hour.

Also consider how you feel. If you feel sober, consider taking the test. If you still feel intoxicated, then you are probably still above the legal limit.

In any case, if you haven't talked to an attorney, you have to make the decision. Refusing the test will probably result in a suspension, and you might still be prosecuted. For a first offender, a DUI conviction will likely mean a large fine, an expensive attorney, increased insurance costs for the foreseeable future, and an embarrassing ordeal. First offenders, however, rarely go to jail and frequently maintain driving privileges. It is another story for repeat or chronic offenders.

Never agree to take a blood test if you are arrested for DUI. Blood tests nearly always register higher blood alcohol content than breathalyzers. Use any excuse, like claiming an intense fear of needles.