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Reliability: Flooded Sample Chamber 2

My 66 series 5000 with the flooded sample chamber is still drying out. Initially I would receive a "Processor Error" flag on startup because the DVM was fluctuating so wildly. Now the instrument starts and produces a "Diagnostics OK" on almost every startup. It is important to note that these types of startup fails or passes are NOT saved in COBRA data. The operator can safely keep trying to start the instrument again and again until a "Diagnostics OK" is indicated. Unless the operator documents such failures on paper, no one will ever know. Simply turn the power button off, wait a minute, turn it on, wait for a "Diagnostics OK", and repeat if necessary.

Once the "Diagnostics OK" is achieved on startup and the DVM has stabilized somewhat, it is pretty easy to run a stand-alone Esc Esc D diagnostics test to establish that all is well with the electronics (even though the DVM is still fluctuating). The 8000C Training Aid in Ontario says that this will indicate that the instrument is in proper working order. This type of data, on a stand-alone Diagnostics test, is stored in COBRA on the 8000C.

Esc Esc D
Diagnostics Passed on Esc Esc D stand-alone Diagnostics check

It is also pretty easy at this stage to generate a passed Esc Esc B test card to show, according to the 8000C Training Aid, that the instrument is capable of receiving a breath sample. Note that when a qualified technician runs a self breath test Esc Esc B he or she usually has no alcohol in their body. The instrument is processing 0 difference in DVM - the instrument is only dealing with zero readings. With an instrument in this bad condition and as long as zero hasn't dropped below true zero (see purge fail examples in previous blogs) it is still pretty easy to generate a clean Esc Esc B if you try several times. This data is NOT stored in COBRA in the 8000C.

Esc Esc B test
An ABA test, Esc Esc B, also known as a self-breath test.

The difficulty comes when you try to get consistent stable control checks using Esc Esc C to establish that the instrument is properly calibrated. The DVM is still fluctuating and so even though some cal checks (94 and 91) are in the acceptable range, many cal checks are too low or the instrument perceives that acetone or another interferent is present. This data is stored in COBRA on an 8000C. On a 5000C or 8000C (the instrument below is a 5000) you would have a separate test card for each stand-alone cal check so bad cal checks (such as 89, 81, and 82) could be discarded safely unless the defence has access to COBRA that documents all sequences.

Intoxilyzer test card
Sequence of 5 cal. checks run back-to-back with results of 89, 94, 81, 82, 91. In two of the cal. checks the instrument is erroneously identifying an interferent.

I have been experimenting with running a large number of air blanks and stand-alone cal checks with no simulator attached. My primary purpose is now to dry out the interior of the instrument. So far cal checks sometimes are good but often are unstable. I will keep trying.

Please note that these videos and blog entries are NOT evidence. They cannot be used in Court. Your lawyer will need to retain an expert scientist.


This blog article was originally published at impaired-driving.com a number of years ago. It is still relevant to an understanding of how a flooded sample chamber and aging instrument, as it dries out, can sometimes produce clean diagnostics checks, clean ABA checks, and clean cal. checks (as long as you throw out the bad ones e.g. the 89, 81, and 82 above and keep the good ones), but unreliable cal. check and subject test results due to wandering DVM. Approved instruments need to be properly maintained at regular calibration intervals to ensure that the DVM is "rock-steady". Police need to be transparent by producing COBRA data of all cal. checks so that this phenomenon can be excluded as a possibility, paricularly in aging instruments.


Section 320.34 of the Criminal Code states:


320.34 (1) In proceedings in respect of an offence under section 320.14, the prosecutor shall disclose to the accused, with respect to any samples of breath that the accused provided under section 320.28, information sufficient to determine whether the conditions set out in paragraphs 320.31(1)(a) to (c) have been met, namely:

  • (a) the results of the system blank tests;

  • (b) the results of the system calibration checks;

  • (c) any error or exception messages produced by the approved instrument at the time the samples were taken; ...

The difficulty for the Defence is that the police may not disclose ALL system calibration checks or ALL error or exception messages produced by the instrument (e.g. a failed diagnostic card or a failed cal. check). Alternatively, the Crown or police may take the position that the failed diagnostics or failed cal. check is not "produced by the approved instrument at the time the samples were taken". The defence can only obtain a complete picture if COBRA data of diagnostics and cal. checks for a bracketing period is disclosed. See https://canlii.ca/t/g8wj8. A failed Diagnostics, when the police used the "turn it off and turn it on again" method, will not show up in COBRA because start-up Diagnostics do not appear in COBRA and because "powering off" destroys recent events in short-term memory.

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