Do Personal Breathalyzers Work?

April 28, 2016

Drunk driving has been a very large problem in the US ever since the advent of the automobile. Over the last 15 to 20 years, however, significant progress has been made in reducing the number of drunk driving related accidents each year. Through a number of state, local, and non-profit education programs which often partner with local law enforcement agencies, the general public has been somewhat protected from the dangers of drivers under the influence. Still, the problem persists.

A number of companies have come up with solutions to help reduce the number of drunk drivers on the road. There are “drunk cabs”—a free service to take intoxicated people home without them having to drive. There are designated drivers. There are even personal blood alcohol calculators. BAC calculators have seen an increase in interest and some device manufacturers have even paired their technology with your smart phone. While this is incredibly creative, is it effective?

Personal Breathalyzers Are Accessible, but Are They Reliable?

Personal breathalyzers have been around for a while. There are a number of websites offering this service in an effort to provide the drinking public with a means of knowing what their limits are before they start drinking. The idea is that if you know your limit before you go out, you won’t over-consume. Of course, that’s not always how it works out.

Some inventive individuals have recognized that self-control isn’t everyone’s forte. So to help out those who may have drunk a bit more than they were supposed to, these companies have produced a portable Breathalyzer to make sure you don’t take that step from having one drink too many to getting behind the wheel of a car.

Since they are portable, you can take these BAC testers out to the bar in your back pocket and then use it when you’re getting close to calling it a night. In a perfect world, you’d see your BAC and make an informed decision as to whether or not you are OK to drive. In practice, however, these devices should never be used to gauge whether someone is safe to drive a car. The only ‘safe’ strategy to avoiding a DUI is to plan your route home prior to beginning your night, whether it is a taxi, a designated driver, or mass transit.

The reliability of personal breathlyzers are up for debate. For something that is designed to be portable they are sturdy on the outside, but often contain delicate parts. If the internal parts are jostled too hard, the device may not work properly. This means the device may be unreliable, considering it’s intended to be carried by someone who is drinking.

Factors a Breathalyzer Can’t Adjust For

Most Breathalyzer function of some pretty fundamental science. They aren’t complex devices. The way they calculate your BAC (Blood Alcohol Content or Blood Alcohol Concentration) can be fooled easily (for better or for worse, for you). Here are some things that can screw up a breathalyzer’s reading:

Lung Capacity:

Breathalyzers measure the concentration of alcohol in your breath. If you have a higher than average lung capacity, then one drink will register differently for you than it will for someone with a normal lung capacity. The more air you have in a breath, the more dilute the alcohol will be.

Body Weight:

Similar to lung capacity, body weight has a definite effect on your Breathalyzer results. Let’s say you weight 210 pounds and have 2 beers. Your BAC reading would be higher than someone who weighs 120 pounds and also had two beers.

Health and Lifestyle:

Some chemicals in your body can affect the reading of a Breathalyzer too. For that reason, smokers and people with diabetes or liver conditions are at risk for inaccurate readings.


Breathlyzers used by law enforcement are expensive devices, calibrated regularly by trained professionals, and must be found accurate within a very narrow range. Personal breathalyzers can be found for as little as $20, and rarely if ever enjoy such careful calibration. As a result, the results you might get from a personal breathalyzer can vary wildly. There’s a reason they say ‘for novelty purposes only.’

Differences between Breathalyzers and Blood Alcohol Calculators Matter

Consumers use personal blood alcohol calculators based on the premise that they will accurately tell the user when they are too inebriated to drive.  The problem is that there is often a disconnect between how the blood alcohol calculator and the Breathalyzer work. Blood Alcohol Calculators (such as B4UDrink) forecast your blood alcohol, given variables such as height, weight, age, and drinks consumed over a given period. Breathalyzers measure your blood alcohol, via the amount of alcohol vapor you exhale, but there are many factors at play, and personal breathalyzers are often woefully inaccurate.

For this reason, it appears that Breathalyzers might be a fun toy, but just because they say that you’re good to drive doesn’t mean that you won’t get a DUI, or worse. It’s everyone’s responsibility to take precautions and not leave it up to chance or to inaccurate instruments. If you’re planning on drinking, always have a plan for how you will get home prior to drinking – a ride from a friend, a cab, or a designated driver. It’s the only surefire way to avoid a DUI.

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