What is an air blank on an Intoxilyzer 8000C?

What does an air blank look like on an Intoxilyzer 8000 or 8000C?

What is a blank test?

What is a system blank test?

What does 000 mean on a blank test?

Does the instrument always produce a blank test result of 000 ?

Does the 000 have probative value?


Watch this video.


Every time that you look at a printout from an Intoxilyzer 8000C the air blanks all read 000. Why?


Almost every time you watch an Intoxilyzer screen, the indication on an air blank is 000. Why?


Almost every time you look at COBRA data on air blanks the results are all 000. Why?


As a defence lawyer, you need to understand:

  1. what is happening during an air blank,

  2. what it is that is showing on the screen or on the printout,

  3. what the machine is doing in the background,

  4. when an alarm will go off, and

  5. how subsequent cal. checks, subsequent subject tests, and subsequent air blanks (many of them) will be affected by what the machine is doing during this air blank.


Consider the following explanation given by the manufacturer to scientists at the CFS in Toronto concerning the Intoxilyzer 5000C:


Obtained through a Freedom of Information application

Please note the explanations:

  1. "The values from 0.001 through 0.006 are masked",

  2. "During any given calibration or subject test",

  3. "The lowest value that will appear on the screen is 0.007"

  4. "The instrument just skips displaying 0.001 to 0.006"

  5. "If the value reached at the end of an air blank is 0.020 or greater the 'AMBIENT FAILED' condition will happen." (Note that this is alleged to be 0.010 or greater on 8000Cs in Ontario, but 0.020 or greater on 8000s in Ohio, all subject to software version).

Why are values between 001 and 006 masked? Probably the reason is electronic noise, instability, and ambient interferents or ethyl alcohol experienced by customers.


Where is zero for purposes of an air blank? That is the particularly interesting question for defence lawyers. We know that zero is constantly floating on an IR instrument. The answer is probably that the machine has re-adjusted itself on the previous air blank. One air blank begets zero which begets another air blank which begets zero and so on.


Can a breath tech commit operator error while conducting an air blank? Every CFS expert that I have cross-examined says they don't. But then, why do so many operators change the instrument's source of ambient air by hiding the end of the breath tube under the machine? There is a manufacturer's cradle for the breath tube on both the Intoxilyzer 5000C and the 8000C. I suspect many police are trying to prevent the machine from generating AMBIENT FAILED error tones, that become nuisances for the operators. I doubt that the CFS and RCMP scientists who evaluated the Intoxilyzer 8000C for the ATC, prior to approval by the Minister, stuck the breath tube under the machine during their evaluations.


Watch for powerful fans in the breath room and strange breath tube positions. Cross-examine.


Please note that this blog article relates only to the blank test on the breath tube and alcohol standard inputs to the sample chamber for BAC indication. Please remember that air flow zero (including pressure/time/slope) works in a completely different hardware and electronics system. Where is the Standard Operating Procedure blank test for that system at rest and calibration while flowing? Is that system blank test and system calibration check also contemplated by the wording of section 320.31(1)(a)?

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