Since no one has answered your question !'
I purchased from 'Sharper image' in the states their 'Alcohawk' detector
it is government certified in this country.
Without getting into ones personal habits which are your business only, my opinion is that it is exceptionally cheap insurance.
Whether it is you or someone else that is, shall we say, possibly unfit, a 10 second blow is the difference between calling in sick , or ruining your professional life or worse..
Seems an easy call