One breathalyzer machine can perform many tests per month. With repeated use, its sensor can drift – a gradual decline in its physical and chemical properties (normal wear and tear) that causes it to lose sensitivity.
The sensor can also become saturated with alcohol vapors, smoke or food particles. Besides, exposure to environmental elements, such as high humidity and extreme temperatures, can affect it.
Consequently, a breathalyzer can give inaccurate blood alcohol concentration (BAC) results over time. Readings can be higher or lower than a person’s actual BAC level. That’s why evidential breath testing instruments must be calibrated:
How calibration is done
Calibrating a breathalyzer is done by exposing its sensor to an alcohol vapor or solution of a known, precise concentration and then adjusting the device’s internal settings to match that predetermined standard.
So, the alcohol sample is passed through the breathalyzer for the device to measure the alcohol concentration. If the readings differ from the known value, the unit’s settings are adjusted until the readings match an acceptable target value.
In Texas, the Office of the Scientific Director, a division within the Texas Department of Public Safety (DPS), oversees this process. The department has developed standardized calibration processes and uses certified reference materials that are traceable to the National Institute of Standards and Technology (NIST).
Certified technical supervisors under the authority of the DPS Breath Alcohol Laboratory (BAL) calibrate and maintain evidential breath testing instruments. They regularly calibrate devices, typically every 30 days, and ensure a device’s readings are within the nominal value of plus or minus 0.01g/210 L. Then, they log results into the official state database.
A poorly calibrated breathalyzer can give inaccurate readings. If you believe this happened to you, consider assessing the calibration records of the instrument used to determine if it was well maintained.