DUI Metrology Dictionary
Control test (in the context of the Intoxilyzer)
Since the evidentiary instrument is, at best, only re-calibrated at the Canadian Authorized Service Centre once per year, police, or a scientist running any measurement, needs a rough, in the field, method of checking calibration, at least at some middle value, close to the expected range of results. With wet bath alcohol standard, the contents of the head space (the air) above the liquid in the simulator (that came from the bottle that came from the lab) are pumped through the Intoxilyzer sample chamber to see how well the Intoxilyzer analyzes a "known" sample. For example, if the Intoxilyzer reads a 100 wet bath solution as 97 or 104, then the Intoxilyzer seems to be working within a few mg% if the subject is close to 100 mg%. The wet bath simulator is used to test the Intoxilyzer, not the other way around. You can't use the Intoxilyzer to check the simulator/alcohol standard system. The simulator/alcohol standard system must always be a "known". The Intoxilyzer is the "unknown". Alternatively you can pump dry gas/air gas into an Intoxilyzer 8000C or other approved instrument to do the same kind of control test. If you use a wet bath system you use liquid alcohol standard. If you use dry gas you buy a canister of dry gas in a round cylinder that attaches to the back of the approved instrument. If you use wet bath the alcohol standard liquid/headspace/simulator system needs to be carefully kept at 34 plus or minus .2 degrees Celsius. If you use dry gas, there is no temperature issue, but there is an ambient atmospheric pressure issue.
A "control" in an experiment is constant and unchanged throughout the course of the investigation. It is kept the same throughout the experiment. If the control changes, the experiment is biased. If the vapour coming from the wet-bath simulator is not at the correct temperature specified on the bottle of alcohol standard, then there is no "control". If the Intoxilyzer pump is not working properly or there is a leak in the simulator re-circulating system then there is no "control". See Henry's Law.