Breath Alcohol Concentration (BrAC) and Blood Alcohol Concentration (BAC).
There is two different ways of measuring alcohol concentrations. In certain countries, alcohol limits are determined by the breath alcohol concentration (BrAC), not to be confused with blood alcohol concentration. But most "in field" tests are done with a BrAC method even if the law is based on BAC levels. This is due to the fact that BrAC is relatively fast and almost as accurate as BAC. The BrAC test will indicate if a BAC test is needed and thereafter a BAC test can be done at, for example, the police station or hospital.
Our sensors would not be accepted in the court of law in many countries due to the fact that they are based on the BrAC method, but they could be used at workplaces and by law enforcement officers.
IR spectrum of ethanol C₂H₅OH
The broadest peak in the IR spectrum of ethanol comes from O-H stretches, similar to O-H bonds in water. This absorption at about 2.9 μm. Other strong stretching modes are C-H at 3.3 μm and C-O at 9.5 μm.
References:
http://en.wikipedia.org/wiki/Blood_alcohol_content
http://en.wikipedia.org/wiki/Breathalyzer
http://webbook.nist.gov/cgi/cbook.cgi?ID=C64175&Type=IR-SPEC&Index=2
