DOT Alcohol Testing: Screening vs Confirmation Tests

What's the difference between a screening test and a confirmation test?

A DOT alcohol test happens in up to two steps. The screening test is first: it can be run on either an evidential breath testing device (EBT) or a simpler alcohol screening device (ASD), and its only job is to sort employees into two groups — below 0.02 breath alcohol concentration (BAC), where testing stops and the employee returns to duty, or 0.02 and above, where a confirmation test is required. The confirmation test must be run on an EBT capable of producing a printed, sequentially numbered result and must be a different, more rigorous administration than the screen. Only the confirmation test result is used to determine a violation.

What happens if the screening test result is 0.02 or higher?

Any screening result of 0.02 BAC or above requires a confirmation test — there's no discretion to skip it. Between the two tests, the BAT observes the employee and waits before running the confirmation, in part to rule out residual mouth alcohol inflating the reading. If the confirmation test comes back below 0.02, there is no violation and the employee returns to duty. If it lands at 0.02–0.039, the employee cannot perform safety-sensitive functions for the rest of that duty period (a removal, not a Part 40 "violation" in the strict sense) until a qualified professional clears them or 24 hours passes. A confirmation result of 0.04 or higher is a DOT violation: immediate removal from safety-sensitive duty and referral to a substance abuse professional (SAP) before any return to duty.

What EBT is used for the confirmation test?

The confirmation test must be conducted using an EBT on the National Highway Traffic Safety Administration's Conforming Products List, capable of printing a result with the test number, testing site, device identification, and time. CMI Inc.'s Intoxilyzer line is a common example of an approved EBT platform used for DOT confirmation testing. The device has to be within its calibration cycle and pass its external calibration check on the schedule set by the manufacturer and the employer's program — a confirmation test on an out-of-calibration instrument is one of the more common ways an otherwise valid test gets challenged.

	Screening test	Confirmation test
Device allowed	ASD or EBT	EBT only, on the Conforming Products List
Who can run it	STT or BAT	BAT only
Triggers next step at	0.02 BAC or higher	N/A — result is final
Result used for violation determination	No	Yes

What role does the waiting period play?

Between a positive screen and the confirmation test, the BAT observes the employee and does not let them eat, drink, put anything in their mouth, or belch, since any of those can leave residual alcohol in the mouth that produces an artificially high reading. The confirmation test is run as soon as reasonably possible after that observation window. If a second consecutive screen (or the confirmation itself) still reads 0.02 or above after the waiting period, the confirmation result stands as the official test result for violation purposes.

How does Foster's technician actually run a confirmation sequence?

When a Foster-trained BAT gets a 0.02-or-higher screen, the sequence is deliberate: the employee is kept under direct observation, told not to eat, drink, smoke, or put anything in the mouth, and the BAT starts a timed 15-minute waiting period before running anything else. During that window the BAT fills out Step 1 of the Alcohol Testing Form with the screening result while the employee waits in view. At the 15-minute mark, the BAT runs the confirmation test on the EBT, verifies the printed ticket carries a sequential test number and the correct date and time, and has the employee initial the form. If the confirmation reads below 0.02, the form documents the negative result and the employee returns to duty immediately — there's no ambiguity left hanging.

What trips people up about the waiting period?

The most common field mistake is a BAT starting the confirmation test too early because the employee "seems fine," which can register residual mouth alcohol and produce a falsely elevated confirmation reading that then has to be explained or retested. The second common mistake is letting the employee out of direct observation during the wait — a bathroom trip alone, a phone call in another room — which breaks the chain of custody an auditor or arbitrator will ask about if the result is ever disputed. A documented, uninterrupted observation period is what makes a 0.04-and-above confirmation result stand up when an employee challenges the removal and SAP referral that follow it.

Frequently Asked Questions

Can an employer use only screening devices and skip EBTs entirely?

No. Any employer running DOT alcohol testing needs access to a conforming EBT for confirmation testing, either in-house or through a contracted collection site, because a screening-only program cannot legally determine a violation.

Does a 0.02–0.039 result go on an employee's DOT record as a violation?

It's treated as a "not fit for duty" removal rather than a Part 40 violation, but the employer must still document it and follow the required removal and return-to-duty steps before the employee resumes safety-sensitive functions.

Who trains the technicians who run these tests?

Employers train and qualify their own Breath Alcohol Technicians under §40.213, or contract with an outside collection site staffed by qualified BATs.

Foster Special Instruments provides BAT training and instrument calibration for employers running in-house DOT alcohol testing programs. See the quote page to price a program.