In my opinion blood test is more accurate than a breath test. There are circumstances where a breath test can have erroneously high readings. For example, an erroneously high readings can occur in people with acid reflux. If you belch close to the time you take the test, you'll have a breath with an artificially high concentration of alcohol. In addition, breath testing machines operates under a scientific assumption that not all scientists agree with. On the other hand, blood testing is done with an instrument called gas chromatograph. This is an extremely accurate and standard instrument that's been used in chemistry for years.

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