What if… Air Blank is Not Zero?
Here are a couple of questions from our mail box about air blanks that are specific to the Alcomonitor CC, but can be generalized to all EBTs.
First of all, here’s a little refresher about air blanks. DOT regulations require that an EBT perform an air blank prior to a confirmation test to demonstrate that there is no alcohol remaining in the instrument from a prior test, and that the instrument is starting from zero. Most instruments today automate the air blank procedure so that the operator need only observe the process.
Q. Will the Alcomonitor CC allow the operator to proceed with a confirmation test if the air blank is not .000?
A. No. The Alcomonitor will display the message “High Blank” and will abort the test sequence. Each model of Intoximeter instrument handles this situation in a different way, but as a rule the instruments will not proceed with the confirmation test sequence if the air blank is not .000.
Q. What does the Alcomonitor CC operator do when confronted with the “High Blank” message?
A. DOT regulations allow the operator to start a second test to attempt to get a zero air blank.
If the second attempt to get an air that reads .000 is not successful, then the instrument must be taken out of service. The instrument may be placed back into service upon successfully passing an Accuracy Check (the regulations use the term “External check of calibration.”)
It is rare that an instrument does not give a zero air blank. Possible reasons for a non-zero air blank include an extraordinary high level of alcohol blown into the instrument on a prior test; not waiting an adequate time after a very high positive test (15 minutes is more than adequate); re-using a subject’s mouthpiece that has alcohol in it; foreign contamination on the sensor or air passage of the instrument; and a sensor that is failing and needs replacement.
Joanne Kent says
We have had this issue lately and are stumped. We have a new refurbished machine and the first calibration test that was done came up high blank void 11. We sent our first machine in for the same reason. We have had two rentals and had the same problem with them. Could it be there is something in the air? Some days its ok and others it’s not. Can you help?
Jennie Lee-Pace says
Hello Joanne.
According to the techs in our repair department…
“Common causes of the “high-blanK’ Void 11 are: perfume/cologne on a person or alcohol-based sanitizers/hand-wipes in the vicinity. Or perhaps the instrument was cleaned with an alcohol-based solvent.
Remedy: Remove instrument to another area and try there; confirm no use of perfume/cologne/sanitizers. If the instrument was cleaned with an alcohol-based solvent, let it dry out for about 10-20 minutes, then try again.
Finally, the fuel cell may be worn out or was damaged and is no longer able to “clear” itself of alcohol residue from prior tests.”
You can contact our repair department to speak with a technician if you continue to encounter this issue.