If the first air blank prior to a confirmation test is not zero the BAT can start a second test to try to get a zero air blank. If the second air blank is not zero, the BAT must then do an Accuracy Check (the regulations use the term “External check of calibration”) before using the instrument again. See the relevant section of the Part 40 regulations below.
As a practical matter, the most likely reason the Alcomonitor CC will fail an air blank is an extraordinary amount of alcohol was blown into the instrument, or if the air passage in the instrument is contaminated with alcohol. The alcohol will evaporate over time, and the above procedure is a good failsafe to ensure that all the alcohol is gone from the instrument prior to testing a subject.
[65 FR 79526, Dec. 19, 2000, as amended at 66 FR 41954, Aug. 9, 2001
40.253 What are the procedures for conducting an alcohol confirmation test?
As the BAT conducting an alcohol confirmation test, you must follow these steps in order to complete the confirmation test process:
(a) In the presence of the employee, you must conduct an air blank on the EBT you are using before beginning the confirmation test and show the reading to the employee.
(1) If the reading is 0.00, the test may proceed. If the reading is greater than 0.00, you must conduct another air blank.
(2) If the reading on the second air blank is 0.00, the test may proceed. If the reading is greater than 0.00, you must take the EBT out of service.
(3) If you take an EBT out of service for this reason, no one may use it for testing until the EBT is found to be within tolerance limits on an external check of calibration.
(4) You must proceed with the test of the employee using another EBT, if one is available.
(b) You must open a new individually wrapped or sealed mouthpiece in view of the employee and insert it into the device in accordance with the manufacturer’s instructions.
(c) You must ensure that you and the employee read the unique test number displayed on the EBT.
(d) You must instruct the employee to blow steadily and forcefully into the mouthpiece for at least six seconds or until the device indicates that an adequate amount of breath has been obtained.
(e) You must show the employee the result displayed on the EBT.
(f) You must show the employee the result and unique test number that the EBT prints out either directly onto the ATF or onto a separate printout.
(g) If the EBT provides a separate printout of the result, you must attach the printout to the designated space on the ATF with tamper-evident tape, or use a self-adhesive label that is tamper-evident.