Abstract: A breath analyzer is provided to test for the presence of an unknown infrared energy absorbing compound in a breath sample collected from an individual. Infrared energy of at least two wavelengths is passed through the collected sample. The first wavelength of infrared energy, 3.48 microns for example, is selected to be significantly absorbed by a predetermined infrared energy absorbing compound, such as ethanol. The second wavelength of infrared energy, 3.39 microns for example, is selected to be significantly absorbed by other infrared energy absorbing compounds, such as acetone. The infrared energy remaining in the first wavelength after its passing through the breath sample is compared to the infrared energy remaining in the second wavelength after its passing through the breath sample. The lack of a predetermined comparison value indicates the presence of an infrared energy absorbing compound other than the predetermined infrared energy absorbing compound.