>-          What about a couple of ultrasonic transducers and measuring the
>propagation delay?
>
>
>  
>
should work very good, ...
... you even determine the mollmass.
You know that the expired air is 36..37 C,
100% saturated with water,
contains ...% CO2
contains ...% O2
so you might even detect the alchol directly through mollmass.

Stef Mientki
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