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Smartphone-Linked Breathalyzers May Not Detect Alcohol Levels Over The Legal Limit


Francesca Benson

Junior Copy Editor and Staff Writer

clockMay 10 2021, 17:15 UTC
drunk driver

Preventing people from getting behind the wheel while inebriated is essential for public safety. Image Credit: nikamo/

The WHO estimates that between 5 and 35 percent of all road deaths are alcohol-related. According to the Centers for Disease Control and Prevention (CDC), in the US alone, around 29 people each day die in a motor vehicle crash involving an alcohol-impaired driver, adding up to a total of 10,497 in 2016. Knowing how dangerous and potentially fatal drunk driving is, preventing people from getting behind the wheel while inebriated is essential for public safety.

Given the fact that people usually cannot accurately determine just how drunk they are, handheld breathalyzers paired to a smartphone seem to be a great tool for people to test themselves before making potentially risky decisions. However, a new study published in Alcoholism: Clinical & Experimental Research has shown that the accuracy of these smartphone-linked testing devices varies wildly.


"Currently, the Food and Drug Administration doesn't require approval for these devices – which would involve clearance based on review of data accuracy – but it should reconsider this position in light of our findings," said lead investigator M. Kit Delgado, assistant professor of Emergency Medicine and Epidemiology at the University of Pennsylvania, in a statement.

Roughly 90 percent of ingested alcohol is broken down by the liver, while the rest is released in urine and breath. Breathalyzers take the amount of alcohol in the breath and use it to calculate the amount in the blood. The study compared the results of six smartphone-paired breathalyzers – BACtrack Mobile Pro, BACtrack Vio, Alcohoot, Floome, Drinkmate, and Evoc – against the police-grade Intoxilyzer 240 and blood alcohol concentration (BAC) measured via the blood.

Researchers took 20 moderate drinkers and gave them three doses of vodka over 70 minutes, with the goal of getting them merry enough that their BAC was around 0.10% –  over the US drinking limit of 0.08%. The participants were breathalyzed with the Intoxilyzer 240 and a smartphone-linked device after each round, with blood drawn after the third vodka drink for the most accurate reading.


Surprisingly, all seven devices – including the police-grade device – underestimated BAC by over 0.01%. The Floome, Drinkmate, and Evoc consistently gave lower than accurate readings, with Drinkmate and Evoc failing to detect when someone was over the driving limit 50 percent of the time relative to the Intoxilyzer 240. BACtrack Mobile Pro readings were consistently higher than accurate, with BACtrack Vio and Alcohoot giving the most accurate measurements. BACtrack Mobile Pro and Alcohoot were the two devices most sensitive at detecting when someone was over the legal driving limit.

Shaky accuracy has been an issue raised about all breathalyzers – smartphone-linked or otherwise, as backed up by the reading errors of the police-grade device in this new study. In fact, multiple previous studies have shown other devices used for official purposes have a margin of error that could lead to both false positives and negatives when testing if someone is over the limit.

"While it's always best to plan not to drive after drinking, if the public or addiction treatment providers are going to use these devices, some are more accurate than others. Given how beneficial these breathalyzer devices could be to public health, our findings suggest that oversight or regulation would be valuable," explained Delgado.


"It is common knowledge that you should not drive if intoxicated, but people often don't have or plan alternative travel arrangements and have difficulty judging their fitness to drive after drinking. Some may use smartphone breathalyzers to see if they are over the legal driving limit. If these devices lead people to incorrectly believe their blood alcohol content is low enough to drive safely, they endanger not only themselves, but everyone else on the road or in the car."

As these results show, relying on a breathalyzer test to determine whether you're fit to drive is a risky decision. Instead, it is wise to avoid alcohol if you're going to be driving, have a designated driver in a group going out on the town, or calling a cab to get you safely to your destination.


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