Choosing a Breath Alcohol Testing Instrument
So your program has decided to implement breath alcohol testing and your boss has given you the task of choosing a breath alcohol testing instrument to purchase. You don’t know the first thing about alcohol testing instruments except that the price ranges from less than $100 to over $1,000. Here are three of the most important things to consider as you evaluate different alcohol instruments.
1: What type of sensor does the instrument use? There are two widely used types of sensors: fuel cell (also called electro-chemical oxidation sensor), and semi-conductor. Fuel cell sensors have a number of advantages over semi-conductor sensors, and are significantly more costly than semi-conductor sensors. Advantages of fuel cell sensors include:
- Greater accuracy and precision – every instrument on the National Highway Traffic Safety Administration (NHTSA) Conforming Products List of Evidential Breath Testing Instruments uses a fuel cell sensor.
- Capable of measuring very small volumes of breath – allows use of breath sampling technology (See #2 below).
- Responds only to alcohol – rules out false positives from acetone and other substances that might appear on a person’s breath.
- Can be calibrated with alcohol gas standards – gas standards are much more convenient to use than the alternative wet bath simulator. (See #3 below.)
Virtually all the inexpensive devices designed for personal use have semi-conductor sensors because semi-conductor sensors themselves are inexpensive. Note that some semi-conductor devices that were designed for personal use are marketed for professional use. With few exceptions, any device selling for less than $300 uses a semi-conductor sensor.
Semi-conductor devices are not necessarily specific to alcohol and may respond to other substances in the breath. For this reason, devices using semi-conductor sensors do not appear on the NHTSA list of evidential instruments.
2: Does the device have automatic breath sampling? Breath sampling means that the instrument measures the alcohol in only a small portion of the breath that a subject blows into the instrument, rather than measuring all the alcohol in the entire exhalation. It’s the same idea of a blood test: rather than draining all five liters of blood from an individual to measure alcohol in the entire volume of blood, a technician draws a sample of a few CC’s of blood to measure for alcohol.
Automatic breath sampling means that the device determines the optimum moment to capture the breath sample and then takes the breath sample without the need for the operator to make any judgements about the adequacy of the breath sample or to press a button to take the breath sample.
Automatic breath sampling has the following advantages:
- Greater precision – removes variability caused by differences in how subjects blow.
- Reduces operator error – the operator only needs to hold the instrument and instruct the subject when to blow.
3: Is it feasible for the operator to check the accuracy and calibrate the device? The minimum standard for professional use is for the operator to have the capability to verify the accuracy of the instrument. This enables the operator to know with confidence that the instrument is giving accurate results, and alerts the operator when the instrument is not giving accurate results. Having the capability for the operator to re-calibrate the instrument when it no longer reads accurately allows the operator to quickly put the device back into service.
Here is where one can distinguish a device that is designed for personal use and a device that is designed for professional use. Manufacturers of devices designed for personal use typically don’t expect users to verify the accuracy of the instruments, or to re-calibrate them. They recommend sending the device back to the factory of re-calibration, or periodically replacing the sensor with a “pre-calibrated” sensor. While that might sound very convenient to a consumer, it begs the question of how do you know for certain that the device is giving an accurate reading right here and now?
The capability for the operator to check the accuracy and to re-calibrate an instrument when necessary has the following advantages:
- Greater confidence in test results – the operator can check the accuracy of the instrument immediately after a positive result to validate the test result.
- Less out-of-service time – accuracy checks and calibration adjustments take only a few minutes, so the instrument is never out of service very long.
- Defend-able test results – the question “How do you know your instrument is reading accurately?” is one of the first questions asked when a positive test result is disputed. Documenting the accuracy check performed immediately prior to or after the test answers that question.
That should be enough to get you started on your search for a breath alcohol testing instrument. There are many more considerations too numerous for this article (regulated vs. non-regulated testing, evidential vs. non-evidential testing, printing capability, passive test features, memory features, etc.). An easy way to get started is to speak to one of AlcoPro’s knowledgeable customer service representatives who can guide you through the process of choosing from among the many alcohol testing instruments available.
Gloria Durst says
I appreciate how you say that you would want to consider the confidence in test results when choosing an alcohol test. It would be good to consider this because you would want to know for sure. In addition, you may need to consider the margin of error.