What happens to ambient fail system if ambient conditions change gradually?
Let's suppose that we have an Intoxilyzer approved instrument (in this case an Intoxilyzer 5000) in a police breath room where ambient conditions are changing all the time (e.g. the room was painted, some standard alcohol solution was spilled, the police officer wiped her boots on a paper towel on the floor, a heavily intoxicated person was recently in the room). The changing ambient conditions in our scenario may include either ethanol (drinking alcohol) or an interferent such as a hand cleaner.
IR evidentiary breath instruments always need a zero starting point. The ambient fail flagging system triggers at about 19 mg / 100 mls on an Intoxilyzer 5000 or 5000C and at about 10 mg / 100 mls on an Intoxilyzer 8000 or 8000C. The set point may vary by state or province.
The problem is that the 19 or 10 mg/ 100 mls threshold assumes an accurate zero. But changing conditions, as simulated in this experiment, may produce numerical results on the instrument screen and the test record that have no meaning in reality without triggering an ambient fail.