The machine uses infrared principles to test the alcohol concentration in a breath sample. A beam of infrared light passes through the chamber and measures the concentration of alcohol molecules based on the reduction of energy as the beam passes through the sample. The breath sample is tested inside a sample chamber which is about the size of a yellow highlighter. The DataMaster DMT breath testing instrument is designed to undergo a number of processing steps prior to the capture and reporting of a subject breath test result. These steps include checking components for function, monitoring heated zones, adjusting a measurement baseline to ambient air, checking detector response, introducing a simulated breath containing alcohol vapor, ensuring sample cross-contamination is prevented, and measuring the quality of breath sample.

The Datamaster DMT breathalyzer is the primary breath testing device used in Los Angeles County for DUI cases. The machine has been around for approximately 20 years and replaced the CDM model for the Los Angeles County Sheriff’s Department Crime Lab. The instrument is used by most cities in LA, including Redondo Beach, Torrance, Rancho Palos Verdes and El Segundo, Manhattan Beach, Rolling Hills, Lomita and Hermosa Beach just to name a few.

The machine can display a number of different errors or error codes that indicate various problems that occur during the testing process. One of the most common problems is the “blank error” code which simply means the machine could not achieve a zero alcohol reading when it went into the sampling process.

According to the manufacturer , the instrument “obtains a reading greater than .003 during the blank test”. You see, the device sucks in a small amount of outside or “ambient” air and runs it through the sample to ensure it reads zero for alcohol, this is called the “blank test”. During this process the air could be contaminated with alcohol from hand sanitizer or cleaners and it gets pulled inside the machine. Hence the term “blank error”.

The device manufacturer also has this to say about the “blank error” message: The Datamaster DMT may have detected a strong presence of alcohol near the instrument. It may be beneficial to ventilate the area prior to running an additional test.

According to experts, the best practice is to air out the room and ventilate the area as well as wait 15 minutes to retest the subject because whatever was contaminating the ambient air also likely contaminated the subject. The manufacturer also recommends ventilating the sample chamber for a minimum of 5 minutes.

This error is not necessarily a big problem as long as the proper procedures are followed to remove the contaminated air. However, if the contamination has not been removed it can continue to affect the testing process by contaminating the air the subject breathing inside the room. Failure to address the error code can be the cause to a challenge of the reliability of any sample obtained in close temporal proximity to the code being displayed.

Matthew Ruff is a local DUI Attorney in Torrance California. With over 25 years experience in criminal defense, Matt is here to defend clients charged with driving under the influence and other serious crimes.