Some of our commonly asked questions have to do with air blanks: what they are, when to conduct them, and how. Here are the answers to those burning questions:
What is an air blank?
An air blank, or blank check, is a test to insure there is no alcohol present in the sampling system of an EBT instrument prior to having a subject provide a breath sample. Such a test is needed to prove that the subject’s test result is not contaminated by residual alcohol.
When must an air blank occur?
An air blank must be performed and the result shown to the subject prior to a confirmation test. Reference 49 CFR Part 40.253(a).
What if no air blank is conducted?
If an air blank is not performed prior to a confirmation test, then the test could be cancelled. 49 CFR Part 40.267(c)(2-3). All Intoximeters EBTs test for residual alcohol prior to all tests and will not proceed if the device detects alcohol present inside the unit. In many cases, these procedures occur in the background and may not appear on the display or print out.
What if the result of the air blank is not .000?
If the Intoximeters device detects alcohol in the sampling system during the air blank, the test will be voided. The BAT should wait a few moments to allow the unit to purge itself of any residual alcohol from a previous test and then initiate another test sequence to complete the test process. It is important to note that the BAT is allowed to try one more time – if on the second attempted test another high blank is experienced, that instrument must be taken out of service until a successful accuracy check is performed. 49 CFR Part 40.253 (a)(2-4).
What can cause an air blank to detect alcohol inside the EBT?
There are several reasons why an EBT might detect alcohol inside the EBT device during an air blank:
- using an alcohol based hand sanitizer
- re-using mouthpieces
- conducting the test in a location where alcohol fumes are present
- user error
Failed air blanks are not common. Strictly following the display prompts on your EBT instrument can help make sure that all tests are performed correctly.
For more details about your specific EBT device, please contact the Intox Training Academy at training@intox.com.