There are two procedures required to maintain any breath alcohol testing instrument in accurate condition. One of the procedures is called a Calibration Adjustment. The second procedure is called an Accuracy Check. Our experience is that many people use fuzzy terminology and refer to both procedures as “Calibration.” Understanding the difference between the two procedures and using the correct terminology to refer to each procedure is critical to maintaining alcohol testing instruments in good condition.
An Accuracy Check documents that a device is, or is not, reading correctly. To perform an Accuracy Check the operator performs a test on an Alcohol Standard, usually an Alcohol Gas Tank. (This is the same idea when testing a drunk person that you know exactly how drunk they are.) The operator then compares the test result against the known alcohol concentration in the alcohol gas tank to see how accurately the alcohol tester reads the standard. An Accuracy Check result that is within an allowable range, for example +/- 0.005, is considered accurate and acceptable.
Best practice is to perform an Accuracy Check at least once a month and to record the results in a log to document that the instrument is reading correctly.
If the results of an Accuracy Check show that the Alco-Sensor is not reading correctly (higher or lower than the allowable range of error) then a Calibration Adjustment is required to make the instrument read accurately once again. The exact procedure to perform this is different for each type of device. Many testing programs, such as the Dept. of Transportation (DOT) workplace alcohol testing program, require that operators be trained and certified to perform the calibration adjustment procedure.
Best practice regarding the frequency of calibration adjustments depends on the manufacturer’s Quality Assurance Plan (QAP). Intoximeter’s QAP does not require periodic calibration adjustments. Other manufacturer’s QAPs require their instruments be calibrated annually or semi-annually.