This paper proposes an advanced and reliable alcoholic-intake detection method that analyzes the subject's photoplethysmogram (PPG) signal. Since smoking and physical exercise as well as alcohol intake are crucial determiners of the body's response, we must analyze how they influence the PPG signal in detecting alcohol intake. In contrast to past studies, it is revealed that the respiratory signal is very useful for alcoholintake detection regardless of smoking and physical exercise, and a more reliable alcohol intake detection method is demonstrated. The proposed analytical methods consider not only the harmonic intensity ratio of the PPG signal, but also the oxygen-saturation level (SpO 2 ) in the artery.

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