Ambient Interferents Compromise Reliability of Control Tests

Updated: Oct 5


Tip 48: The reliability of control tests using the alcohol standard in a wet-bath #duisimulator may be compromised by the presence in the breath room air of an interferent, if the approved instrument confuses the interferent as ethyl alcohol. In the same way that ambient ethyl alcohol can raise the zero baseline, so can an ambient interferent. Interferents may include paint, cleaning fluids, fingerprint cleanup fluids, and chemicals on the clothing or breath of the accused or the qualified technician.

Greater research needs to be done on the subject by scientists at the Centre of Forensic Sciences, by the Alcohol Test Committee, and by scientists in private practice. Further inquiries need to be made of the manufacturer as to the exact bandwidth of the IR filters on the 8000C.

The video below is NOT expert evidence. It is provided as an aid to defence counsel in understanding the problem of chemical "interferents" in evidentiary breath testing generally, and wet-bath simulator cal checks specifically. We need to discuss these issues and obtain better answers from the scientific community.

The following data was used during argument in R v O and was filed as part of Exhibits 2 and 9 on the Application. The data was originally filed in R v H at Brampton. The data reveal that the instrument flagged an "interferent detect" message during stand-alone calibration checks. Unless the alcohol standard from the lab, or the wet-bath simulator cleaned/rinsed/lubricated by a QT, was the source of the interferent, the cause of this fail must have been the ambient air in the breath room.

COBRA data showing Interferent Detect during Control Checks
Excerpt from Exhiibit 2 in R v O

Breath rooms frequently contain cleaning equipment associated with fingerprinting. The following is an image captured in [a local] police breath room by the professional photographer hired by the defence in R v G. Notice the reference to D-Limonene under First Aid Treatment. D-Limonene is a problem interferent for the 5000C.

Hand  cleaning product containing D-limonene.
Image taken by defence photographer in a GTA breath room

With respect to the Intoxilyzer 8000C, defence lawyers should be watching for evidence of ethyl ether or di-ethyl ether in the breath room. Some office cleaners use these dangerous chemicals for deep cleaning without dilution. These chemicals are also commonly used by diesel mechanics, personal watercraft mechanics, and hobbyists.


#interferent #ambientfail #reliability #tip

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