Breath alcohol triangle (BAT)

• Forschungsstelle: METAS
• Projektnummer: F-5232.30097

Schlüsselwörter (Englisch)

Breath alcohol, Dubowski method, traceable reference gas mixtures, MIR laser spectroscopy

Kurzbeschreibung (Englisch)

Various discrepant reference systems are used worldwide for the adjustment and testing of breath alcohol measuring instruments. This not only makes it difficult for the manufacturers to correctly adjust their globally used measuring instruments, but also requires that the legislation must opt for one of the reference systems. Switzerland has opted for the saturation method according to Dubowski (OIML R126) in the Ordinance on breath alcohol AAMV.

So far, it has been difficult to reliably detect the discrepancies of between 2 and 4% relative to the lack of suitable selective instruments, as these were in the area of uncertainty of com-mercial instruments. The ethanol-laser absorption spectroscopy (Alcolaser) developed in a previous project, which can simultaneously measure the CO2 and water mass fraction, makes it possible for the first time to record the differences between the various reference systems with the re-quired accuracy and selectivity.

The two main established reference systems (dry gravimetry and saturation method according to Dubowski) are to be supplemented by a third method of the SI-traceable dynamic generation (improved version of the design developed in the project 'SI breath alcohol generator' (2013)). This method is based on novel ways of dosing and calibrating smallest flows of liquid ethanol / water mixtures. (Link to Project HLT07 MeDD).

The results should be published to induce a revision of the Dubowski saturation method.

Projektziele (Englisch)

The objectives are:

• A generator for gaseous ethanol mixtures in close-to-reality matrix (humid, CO2-containing air) is fully functional and delivers amount fractions of ethanol with a relative stability of < 0.3 % and an extended relative measurement uncertainty of 1 % in the range of (50 ... 500) μmol / mol.
• The tools for the evaluation and MU determination of the generated and measured mix-tures are created and prove to be practicable.
• Three comparisons between any two reference systems (in addition to the generator: dry gravimetry diluted and existing Dubowski saturation method) are performed using the MIR ethanol laser spectrometer and provide reproducible results with appropriate stability and resolution.
• An article with the results obtained is submitted to a peer-reviewed journal for publication.