There should be nothing surprising about this. Any physiological characteristic of a human being, -subject as it is to thousands or millions of morphological variations caused by the fuzziness of biological creation- can quickly become a unique identifier. All you need is a method for quantifying it. We started with fingerprints in the 19th century, now we have man others, and especially DNA. Respiratory "fingerprints" aren't useful in the sense that they're left behind like DNA or fingerprints, but as a biometric marker, they make sense.
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