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How does a DOT breath alcohol test work?
Last Updated: 09/24/2026
A DOT breath alcohol test measures alcohol concentration in the employee's breath at the time of the test. It is done in two stages (49 CFR Part 40, Subparts L and M):
- Screening test by a trained Breath Alcohol Technician (BAT) or Screening Test Technician (STT), using an approved device. A result below 0.02 is negative.
- Confirmation test if the screening result is 0.02 or higher, done by a BAT on an evidential breath testing device after a waiting period of at least 15 minutes (49 CFR 40.251). The confirmation result is the official result.
The results are recorded on the DOT Alcohol Testing Form. When the test is done at a Med-Stop location, the result appears on the test record in Med-Stop.
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