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Also known as "interferent bias"
Evidentiary breath instruments are designed to alert the qualified technician if an interferent, such as acetone, is detected on the breath of the test subject. The ethanol molecule's IR signature has similarities at certain wavelengths to acetone, methanol, and isopropanol. This means that if a breath instrument is not designed to alert the qualified technician as to the presence of an interferent, then acetone, methanol, isopropanol (if present on the breath or in the room) could falsely elevate the breath readings. Evaluation of evidentiary breath instruments requires that particular substances that are produced endogenously and could be present in human breath, be tested to determine if they could create such an interferent bias.
Non-evidentiary screening devices usually do not contain the hardware or software necessay to alert for or subtract for other alcohols such as isopropanol. The presence of a substance such as isopropanol can damage a fuel cell sensor.
The Effect of Volatile Substances on the Intoxilyzer 5000C Breathtesting Instrument
Isopropanol Interference with Breath Alcohol Analysis: A Case Report
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Excerpt from the Alcohol Test Committee Recommended Standards (2003):Can. Soc. Forens. Sci. J. Vol. 36. No 3 (2003) pp. 101–127
At page 104:
A. Approved Instruments “Approved Instrument” means an instrument of a kind that is designed to receive and make an analysis of a sample of the breath of a person in order to measure the concentration of alcohol in the blood of that person and is approved as suitable for the purposes of Section 258 by order of the Attorney General of Canada [Subsection 254 (l)].2
Instruments presented for evaluation shall be commercially available production units. Where the manufacturer produces Instrument variations, through significant modifications of integral components and functions, the Instrument presented for evaluation shall be clearly identified by a model designation. Manufacturers shall provide a precise set of specifications including schematic drawings of the systems of the Instrument. Actual performance data purporting to satisfy the following standards shall be provided by the manufacturer. Detailed operating instructions shall be supplied with each Instrument.
3. Substances which are produced endogenously and are present in the breath shall not contribute to an apparent BAC by more than 10 mg/100 mL."
and at 118 to 119:
" Individual Standards
A. Approved Instrument
3. Substances which are produced endogenously and are present in the breath shall not contribute to the apparent BAC by more than 10 mg/100 mL.
Tests on twenty alcohol-free human subjects shall not yield a result greater than 10 mg/100 mL.
In addition, the following solutions shall be tested using a simulator maintained at 34.0° ± 0.2°C:
a. aqueous acetone solutions of 5, 10 and 50 mg/100 mL acetone;
b. aqueous solutions containing alcohol (to give an apparent BAC of approximately 100 mg/100 mL) which also contain the acetone concentrations listed in a.
In a series of twenty tests on each of the solutions containing 5 and 10 mg/100 mL acetone, Instruments shall yield results in which the acetone does not contribute to the apparent BAC by more than 10 mg/100 mL. A purge, or an Alcohol Standard and a purge, shall be run between each test to simulate field operation. Test results on solutions containing alcohol shall be interpreted by allowing for variations permitted under standard 4. Instruments sensitive to acetone but designed to detect interference by acetone shall indicate interference in all tests on solutions containing 50 mg/100 mL acetone.
The descriptive information provided by the manufacturer shall be reviewed. If specific mention is made of particular sensitivity to compounds other than alcohol, these shall be tested at concentrations that might reasonably be encountered in a breath sample. If the theory of operation of the Instrument suggests potential problems with this standard, the evaluators shall seek comments from other members of the Committee with respect to appropriate tests. Tests shall then be designed by the evaluators to determine if the potential problem substances may contribute to a BAC reading."
Notes respecting the Intoxilyzer 5000 evaluation in Canada::
In the September 1988 evaluation of the Intoxilyzer 5000 by the RCMP (serial number 64-00285, not an Intoxilyzer 5000C), acetone tests were run at various concentrations. With a 50 mg/100ml acetone only solution the instrument displayed an "Interferent Subtracted" message and the reported result was 0 mg/100mLs. When the evaluators combined the equivalent of 50 mg/100mLs acetone with 100 mg/100mLs alcohol the ressults were in the 101 to 104 mg/100 mLs range with an "Interferent Subtracted" message. However 50 mg/100mLs methanol produced results of 39 to 41 mg/100mLS with no "Interferent Detect" or "Interferent Subtracted" message. Unfortunately no tests were reported using a variety of combinations of methanol, ethanol, isopropanol, and acetone. "Interferent Subtract" makes sense if and only if one interferent is present.
The July 1989 evaluation of the Intoxilyzer 5000 (serial number 65-001001, not an Intoxilyzer 5000C) by the Centre of Forensic Sciences in Toronto with a 50 mg/100ml acetone only solution the instrument displayed an "Interferent" message and the reported result was 0 mg/100mLs. Tests at 5 and mg/100mLs acetone produced 5 "inhibited-RFI" messages. When the evaluators combined the equivalent of 50 mg/100mLs acetone with 100 mg/100mLs alcohol the ressults were in the 87 to 97 mg/100 mLs range with an "Interferent" message. Methanol alone at 100 mg/100mLs produced results of 82 to 86 mg/100 mLS with no "Interferent" message. Isopropanol in the same equivalent concentration resulted in test results of 38 to 42 mg/100mls with an "Interferent" message. Unfortunately no tests were reported using a variety of combinations of methanol, ethanol, isopropanol, and acetone. "Interferent Subtract" makes sense if and only if one interferent is present.
Unfortunately the instruments evaluated in September 1988 and July 1989 prior to approval by the Alcohol Test Committee were Intoxilyzer 5000's (serial numbers 64-00285 and 65-001001) and not Intoxilyzer 5000C's. It is respectfully suggested that the Intoxilyzer 5000C did not exist when it was evaluated and "approved."
Unfortunately, some Ontario police detachments may contain cleaners stored and used in the breath room by qualified technicians that contain d-limonene. This and other cleaners create interesting elevated results when combined with the breath of a subject with a true BAC just under the legal limit. Further scientific testing should be done on the chemicals you use at work if you are a painter, plumber, printer, furniture finisher or floor refinisher.
See also: acetone
See also: acetone
See also: isopropanol
See also: IR
See also: interferent
Links to legislation in International Referral Database:
Ontario : Instrument Test Record Card/Ticket
Breath Instruments Links
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