Myth #7: Breath Test — Breathing Pattern Is Not Important

Breathing pattern is another factor where different operator techniques can lead to disparate results.

With breath holding (30 seconds) before expiration, the concentration of ethanol increased by 15.7 ± 2.24 percent (mean ± SE) and the temperature of breath rose by 0.6 ± 0.09o C. . . . Keeping the mouth closed for 5 minutes (shallow breathing) increased expired ethanol concentration by 7.3 ± 1.2 per cent and the breath temperature rose by 0.7 ± 0.14o C. After a slow (20 second) exhalation expired ethanol increased by 2.0 ± 0.71 percent but breath temperatures remained unchanged from control tests.
A.W. Jones, How Breathing Technique Can Influence the Results of Breath-Alcohol Analysis, 22 (4) Med. Sci. Law 275, 275 (1982).