"The body metabolizes alcohol rapidly, but alcohol will be detectable in breath as long as it is present in blood. The detection period for ethyl alcohol itself is hours (not days) after the last alcohol use. The metabolism of alcohol varies considerably by the person’s gender, age, physical condition (especially the condition of the liver), and weight.
"Easily administered breath alcohol tests are available to confirm alcohol ingestion within the past several hours. When a breath alcohol analyzer test is conducted properly, it gives an accurate measurement of breath alcohol content (BrAC). The BrAC gives an estimate of blood alcohol level (BAL) (Watson et al., 2006). Body temperature and breathing patterns can affect breath alcohol test results. Compared with blood and urine tests, breath tests are less precise. Some evidence suggests that breath tests may underestimate BALs by approximately 8.5 percent (Garriott, 2008).
"The breath alcohol analyzer (such as the best-known version, Breathalyzer) is a device that gives an accurate BrAC."
"Clinical Drug Testing in Primary Care," Technical Assistance Publication (TAP) 32, Substance Abuse and Mental Health Services Administration, Clinical Drug Testing in Primary Care (Rockville, MD: U.S. Department of Health and Human Services, 2012), p. 23.