Partition Ratio

Partition Ratio2019-02-22T03:13:41+00:00

You are probably wondering how the government is charging you with DUI based on your alleged blood alcohol content (“BAC”) when you submitted to a breath test that produced a breath alcohol content (“BrAC”).  The answer is simple; your reported BrAC is actually your alleged BAC.  The Intoxilyzer that was used to analyze your breath sample for alcohol content converts your alleged BrAC to its corresponding BAC.  This conversion is calculated using the “partition ratio.”

The “partition ratio” also known as the blood-breath ratio is the ratio between the alcohol dissolved in the blood to the alcohol exhaled in the breath.  This conversion principle is based upon Henry’s Law.  The partition ratio used in the United States assumes that 2,100 parts of breath contain the same amount of alcohol as 1 part of blood.  Yes, this means that the partition ratio is an average, not a scientific law.  Actual partition ratios have been reported as low as 1,300:1 and as high as 2,700:1.  In Great Britain and Holland, a partition ratio of 2,300:1 is used.  Austria uses a 2,000:1 partition ratio.  This means that your alleged blood alcohol content is based upon what the average person’s partition ratio is, not what your actual blood alcohol content was.  In fact, the 2,100:1 partition ratio that Nevada uses results in 20% of the population’s reported BAC’s being overestimated.  It is possible to determine your true partition ratio under controlled laboratory settings.  A “partition ratio defense” is worth looking into in cases where your BAC is alleged to be at or close to the legal limit.  If you would like to discuss a potential partition ratio defense, contact the DUI Lawyers of Las Vegas to schedule a free and confidential consultation.