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  • Stephen Biss

Do hand cleaner chemicals in the air affect breathalyzer reliability?


This experiment explores the possibility that chemicals in the air can affect the reliability of calibration checks that are used to establish the reliability of evidentiary breath tests.

Different IR approved instruments may be affected by different interferents (chemicals that simulate alcohol in the breath analysis). Instruments only examine one to five points on the IR spectrum (8000C uses two, 5000C uses three, 5000EN uses five) and there are chemicals that resemble ethanol at those wavelengths. Manufacturers are very tight-lipped about the bandwidth of the IR filters they use. The machine may get information it isn't supposed to get about chemicals other than ethanol. More wavelengths coming through cause confusion. The instrument may interpret that additional absorption in the wrong way because the machine is designed to look for ethanol.

If information about Interferent(s) gets through the filters one can't always assume that the interferent(s) will be correctly flagged as interferent(s) because the machine may think it is seeing only ethanol.

Even if the machine sometimes flags a particular chemical as an Interferent the software in the machine may wrongly assume the Interferent is acetone and so use the wrong subtraction algorithm. Interferent Subtraction algorithms are complex and assume that the Interferent is known. If the instrument uses only two filters, like the 8000C, the algorithm ratio beteween the two signals may be thrown off. The machine also can't do Interferent Subtract math to give an adjusted value of BAC or the calibration check if there is more than one Interfernt present.

Watch the video and see the strange ways that the Intoxilyzer 5000 in the experiment interprets the 200 mg / 100 mls alcohol standard in the main simulator, all because the ambient conditions are changing.

Limonene or d-limonene are common ingredients of hand cleaners such as GOJO. Watch for them in breath room videos. These handcleaners are used in breath rooms that double as fingerprint ID rooms at small detachments.

#interferent

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