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  • Stephen Biss

Reliability: Don't Ignore Adverse Conditions


Tip 46: An 8000 or 8000C functioning in accordance with the manufacturer's design will sometimes generate exception messages such as "ambient fail" or "purge fail". Generally speaking, these normal messages are not malfunctions of the instrument itself, but are flags, to a conscientious operator, that something is wrong with the environment of the breath room.

The big questions are: "What is the cause of the exception message?" and "How did the operator respond to the message?" If the message alerts the operator to ambient alcohol (or an ambient interferent that mimics alcohol), then the operator should follow protocol, ventilate the room and remove or control the source of the ambient condition. The operator should not hide the exception / error, but rather, should be transparent about it. The operator should make sure at all times that adverse conditions will not be ignored.

The first two video segments depict the normal response of a properly functioning 8000 / 8000C to adverse ambient conditions.

In the first video segment there is an adverse condition (ambient alcohol) during the first air blank, but no adverse condition during the second. The result is an ambient fail and then a successful air blank.

In the second video segment there is an adverse condition (ambient alcohol) during both the first and second air blanks. The result is an ambient fail and then a purge fail.

The third and fourth video segments depict cal checks (using 45 dry gas standard) that do not result in ambient fails or purge fails.

In the third video segment there is no ambient fail or purge fail because ambient alcohol levels in the room have increased to a point where the ambient alcohol in the air near the instrument, in the breath tube, and in the sample chamber is at least 45 mg/100mls. Zero has been automatically reset by the adverse conditions to at least 45 mg/100mls above true zero. The result is a cal check of 000. The instrument is functioning as designed by the manufacturer but the cal check is completely unreliable because the operator has not properly controlled ambient conditions.

In the fourth video segment there is no ambient fail or purge fail because ambient alcohol levels in the room are close to zero. The instrument resets zero close to its true value and performs a reliable cal check close to 45 mg/100mls using 45 dry gas standard.

These video segments show that an 8000 will behave very much like a 5000 or any other IR evidentiary breath instrument where zero floats depending on ambient conditions.

It should be noted that, during the making of these videos, there were many other sequences not reproduced here, that resulted in ambient fails, purge fails, and low cal checks. These types of experiments need to be run by the scientific community so that expert witnesses can provide assistance to Courts in understanding air blank, ambient fail, and zero adjustment on IR instruments.

#ambientfail #purgefail #reliability #tip

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