What is a Breathalyzer False Positive?

Definition: A test result that is erroneously positive when a situation is normal.
An example of a false positive: A particular test designed to detect Alcohol in breath of a person is positive but the person has not consumed any alcohol.

Before we discuss some possible reasons for a false positive test, one must first consider the breathalyzer percentage of accuracy. With most Breathalyzers having accuracy range of ±10% which is ±.01%  BAC (on the scale of zero to .10% BAC), some false positive readings may fall within the manufacturer's specification.

Having said that, beside alcohol, the sensor inside the breathalyzer deals with gases such as Acetone, Ketones and etc. These gases are normally radiated from our lungs and have very close and some overlap the alcohol detection curve. These side gases are much higher in people with higher level of fatty acids.  Folks on hi protein diet tends to produce higher level of acetone in their breath while a higher level of ketones may indicate a possible diabetic condition.  In case of a  diabetics situation Breathalyzers can falsely read as high as .03% BAC.

Although most Breathalyzers are designed to be very selective to alcohol, but unfortunately in some users these side gases are significant enough to interfere with the test.  We have also learned that subjects with false positive do not always blow positive but only in certain times of the day when their metabolism is most active.

To confirm a false positive, always try your device with friends or family members to see if the majority of them produce false positive.  In that case, contact the device manufacturer for possible calibration or repair.