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  • Stephen Biss

Reliability: Air Blanks


Tip 43: A properly functioning air blank system in the approved instrument is a condition precedent to reliability of the alcohol standard in a wet-bath #duisimulator. Disclosed information about successful air blanks both prior to and and post calibration checks and subject tests is essential to any audit of calibration check or subject test reliability.

It is a requirement of the Alcohol Test Committee that a qualified technician conduct air blanks as part of subject tests. This requirement is included in the 2014 ATC operational procedures at pages 4 and 5:

"2. A system blank test shall be conducted and shall give a reading not greater than 10 mg/100 mL."

"4. Readings for the blank and calibration checks shall be recorded to the nearest milligram and shall not be truncated."

The 2013 ATC Recommended Standards provision read as follows at page 12:

The 2009 ATC Recommended Standards provision read as follows at page 15:

It is a requirement of the Alcohol Test Committee that the person responsible for set-up of an approved instrument, in a detachment or breath truck, pay attention to environmental conditions, including ventilation. This requirement is included in the 2014 ATC best opractices at page 12:

The importance of air blanks in the evaluation of calibration checks was reviewed by Justice Tuck-Jackson in R. v O., 2014 ONCJ 440, based on evidence she had heard from a CFS scientist, called by both Crown and defence. The following are excerpts from that decision:

[50] The first stage is an air blank test. In this phase, the A.I., with the use of a pump, draws in room or ambient air through the heated breath tube. In so doing, the A.I. is checking to see whether there is any alcohol or other interfering substances present in the room air that could contaminate the testing process. As long as the tube is not blocked in any way, the instrument will take an accurate reading of the room air at the time of testing. The positioning of the air tube at the time of the air blank test does not impact the reliability of the air blank test result. The optimal and typical result obtained registers as “000”. In the instant case, the A.I. conducted an air blank test at 04:05:24 on June 8, 2011 at the conclusion of which a result of “000” mg% was generated. In Mr. Palmentier’s expert opinion, that result indicated that the level of alcohol or any interferent that might be present in the surrounding air was 0 to some amount less than or equal to the equivalent of 7 mg of alcohol in 100 mL of blood. If the level of alcohol or any interferent that might be present equals or exceeds the threshold value of the equivalent of 10 mg of alcohol in 100 mL of blood, then an ambient fail message registers. The instrument immediately initiates a second air blank test, following which the testing sequence is interrupted and cancels itself. This represents an example of how the Intoxilyzer 8000C self-regulates.

[51] Assuming that the air blank test result does not exceed the 10 mg per 100 mL threshold value, the A.I. proceeds to the second stage, namely a diagnostics test.

[87] A second potential disadvantage presented by this template, depending, of course, on the needs of the reviewer, is that the volume (that is to say, the number of fields) of COBRA data presented falls far short of the total amount that exists. For example, these templates contain no data regarding the results of air blank tests that necessarily would be run during standalone calibration checks and calibration checks that occur during the testing sequence that includes a subject test.

It is respectfully submitted that a complete series of successful air blanks with results of "000" (full disclosure of all air blanks as per Justice Tuck-Jackson's decision in R. v. O.) should be a good indicator that the IR approved instrument and its alcohol standard are not being affected by adverse ambient conditions that would affect the reliability of the alcohol standard and the subject tests. If there is no significant ambient alcohol or ambient interferent in the room air, then the baseline zero on the IR instrument should not be affected. If so, the reliability of calibration checks should not be affected by ambient conditions.

There is a problem, however, if the supervisor of the detachment or the qualified technician is not paying appropriate attention to ambient conditions, by assuring adequate ventilation and avoiding the presence of interferents (e.g. hand cleaners, cleaning fluids, and fingerprinting chemicals) that may not be detected by the instrument's interferent detect system (e.g. limonene or d-limonene on the 5000C and ethyl or di-ethyl ether on the 8000C) .

There is a second potential problem. In R. v. O., Justice Tuck-Jackson found at paragraph 50 (see above): "As long as the tube is not blocked in any way, the instrument will take an accurate reading of the room air at the time of testing. The positioning of the air tube at the time of the air blank test does not impact the reliability of the air blank test result." Her finding was based on the evidence of Mr. Palmentier of the CFS who was called as a "joint witness" by Crown and defence. The author of this blog respectfully takes issue with that opinion, by Mr. Palmentier, and urges the scientific community to test that hypothesis experimentally. This author's own experiments imply that the hypothesis can easily be contradicted by changing the position of the entrance to the breath tube during air blanks. According to my own experiments, ambient fails can be avoided and IR baselines can be manipulated by changing the position of the breath tube.

Defence lawyers need to pay particular attention to protocols, described in the CFS Training Aid, for ventilation and re-positioning the subject following an ambient fail, not re-positioning the breath tube before any air blank begins. Pre-emptive re-positioning of the breath tube because ambient fails are frequent in a particular detachment is not mentioned as a recommendation in the Training Aid. See page 136 of 238 respecting the Exception Message "Ambient Fail":

"When: During the air blank." "Why: The instrument has detected an unacceptably high alcohol concentration in the ambient air drawn in during the air blank. The ambient fail message is communicated when the difference between the vapours in the sample chamber at cessation of the air blank (i.e., when the pump stops) is more than 10 mg/100 mL higher than the baseline measurement obtained before the pump was activated. An ambient fail message can occur if the test subject moves too close to the external breath tube during the air blank, or if the mouthpiece is not removed after the subject breath test "Action: Relocate the subject away from the breath tube, remove mouthpiece, ventilate the room, re-commence testing of the subject." "A continuous purge can be initiated through the keyboard menu using the “Esc Esc A” command."

It is respectfully submitted that, notwithstanding the finding of Justice Tuck-Jackson in R v O, pre-emptive re-positioning of the breath tube because ambient fails are frequent in a particular detachment is operator error. Defence lawyers will, of course, need to call an expert on the subject. Further experimentation is required to prove or disprove Mr. Palmentier's hypothesis.

#ambientfail #reliability #tip

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Intoxilyzer®  is a registered trademark of CMI, Inc. The Intoxilyzer® 5000C is an "approved instrument" in Canada.
Breathalyzer® is a registered trademark of Draeger Safety, Inc., Breathalyzer Division. The owner of the trademark is Robert F. Borkenstein and Draeger Safety, Inc. has leased the exclusive rights of use from him. The Breathalyzer® 900 and Breathalyzer® 900A were "approved instruments" in Canada.
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