There’s a reason why officers who administer breathalyzers to DUI suspects have the suspects breathe long and hard into the breathalyzer.
According to Dr. Michael Hlastala, professor of physiology, biophysics, and medicine at the University of Washington, different parts of a DUI suspect’s breath exhaled into a breathalyzer will provide different blood alcohol content readings.
Dr. Hlastala said in his article, Physiological Errors Associated With Alcohol Breath Testing, “By far, the most overlooked error in breath testing for alcohol is the pattern of breathing…. The concentration of alcohol changes considerably during the breath…The first part of the breath, after discarding the dead space, has an alcohol concentration much lower than the equivalent BAC. Whereas, the last part of the breath has an alcohol concentration that is much higher than the equivalent BAC. The last part of the breath can be over 50% above the alcohol level….Thus, a breath tester reading of 0.14% taken from the last part of the breath may indicate that the blood level is only 0.09%.”
Breathalyzers are also affected by the breathing patterns of a DUI suspect immediately prior to taking the breathalzyer.
According to the study, “How Breathing techniques Can Influence the Results of Breath-Alcohol Analysis,” holding your breath for 30 seconds before blowing into a breathalyzer can increase the blood alcohol content reading by 15.7 percent.
The study also demonstrated one of the only proven ways to beat a breathalyzer. Hyperventilating for 20 seconds, on the other hand, reduced the blood alcohol content reading of the breathalyzer by 10.6 percent. Simply put, the hyperventilating DUI suspect is replacing the alcohol gas located in the lungs with fresh air.
I wouldn’t rely on this technique, however, to attempt to beat a DUI. Hyperventilating can cause someone to pass out or, at a minimum, get dizzy. Both are also effects of intoxication and both will cause an officer to become suspicious.