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Interferent Detect

This article discusses problems on the Intoxilyzer 8000 that occur when the breath test machine encounters interferent or registers an error / exception message on the Intoxilyzer 8000 for “interferent detect” during a subject test.

Acetone, found in uncontrolled diabetics / diabetic crisis, closely matches the signs and symptoms of alcohol. The instrument will detect acetone and display as an Interferent Detect.

For this reason, a criminal defense attorney knows that if you have a breath test reading with an “interferent detect” error / exception message, then no matter what other readings are taken by the instrument, they can not be trusted to render an accurate or reliable reading to measure an alcohol concentration.

When an interferent detect is noted, the subject should be taken to the hospital because it is possible the subject is having an uncontrolled diabetics crisis. The other possibility is that the Intoxilyzer 8000 is malfunctioning by improperly detecting interferent when none actually exist, which is an even bigger problem.

Definition of Interferent Detect

According to the Breath Test Operator Renewal Course Lesson Plan – August 1, 2015, Version 2015.08, the term “Interferent” is defined as “[a] substance that appears in sufficient non-lethal quantities in the human breath and is capable of being detected by the instrument at these non-lethal quantities. o Acetone is an example of an interferent.  It could possibly appear on the breath of a person who is in diabetic shock or fasting (ketogenesis).”

The breath test operators of the Intoxilyzer 8000 are trained that the Interferent Detect exception / error message will appear when – “The calculated result obtained from the detection of light from each filter did not agree, which could mean that an interfering substance was detected in the breath sample or control sample.”

In these cases, the breath test operators are trained that when the breath test machine displays INTERFERENT DETECT, they must “abort the test, print INT* in the results section of the report, and print *INTERFERENT DETECT.”

Exception Messages for Interferent Detect

A message of “interferent detect” may be displayed to the operator indicating that this error has been identified by the Intoxilyzer 8000 during a subject breath test.

Exception / Error Message Displayed


Best Practice

 Interferent Detect 

A substance other than alcohol was detected in the breath sample. 

Retest subject.
Request a blood or urine sample if second sequence is unsuccessful. 



Examples of Interferent Detect Error / Exception Messages

Additional Resources

Interferent Detect on the Intoxilyzer® 8000C in an individual with an elevated blood acetone concentration due to ketoacidosis, Wallage & Bugyra, Canadian Society of Forensic Science Journal.

This article was last updated on Friday, March 23, 2018.