Three factors that can create false positive breath tests results

A breath test screens blood alcohol concentration (BAC) levels of motorists suspected of driving under the influence. Trained law enforcement administer the test. However, false test results can occur regardless of proper administration.

Learn more about the various ways breath tests results can be inaccurate.

Technical issues

A breath test technician calibrates a breath test device. For correct operation, calibration must take place about every 10 days or 150 uses of the machine.

For an accurate reading, law enforcement must observe the driver for 15 minutes before administering the test. Burping or vomiting in that period can alter test results. Each burp or vomit event restarts the 15-minute time limit over. Law enforcement instructs the suspect to dispose of gum. The officer notes medications or conditions altering accurate results.

Medical conditions

People who have diabetes have high acetone levels. Acetone (diabetic) and ethyl alcohol (drinking) are not the same. The breath test device does not distinguish between acetone and ethyl alcohol levels. A low-carbohydrate, high-fat, high-protein diet can also raise acetone levels in the blood.

Other medical conditions may also give unreliable breath test results, including:

  • Acid reflux
  • Heartburn
  • Gastrointestinal reflux disease
  • Gastroesophageal reflux disease

Sample contamination

Professional painters may receive false readings, due to certain chemicals in paint. Residual alcohol (alcohol leftover in the mouth) is present for 15 to 20 minutes. Accurate test results are not administered before the waiting period.

Other possible breath test contaminants include:

  • Chewing gum
  • Mouthwash
  • Breath sprays
  • Dental appliances
  • Cough syrups
  • Asthma inhalers
  • Vomiting before a test
  • Contaminated breath test mouthpiece

Inform law enforcement of any factors that can skew test results if you face a breath test in a DUI stop.