STT vs BAT: What's the Difference in DOT Alcohol Testing Roles?

Employers setting up a DOT alcohol testing program for the first time often assume they need a Breath Alcohol Technician on staff and stop there, without realizing 49 CFR Part 40 defines a second, more limited role that covers a lot of routine testing. A Screening Test Technician and a Breath Alcohol Technician are not interchangeable job titles for the same work; they are authorized to do different things with different devices, and mixing them up in a written program creates gaps that only surface when a screening result comes back positive and nobody on-site is qualified to confirm it.

What is a Screening Test Technician authorized to do?

A Screening Test Technician (STT) is qualified under 49 CFR Part 40 Subpart J to operate an alcohol screening device (ASD) and conduct the initial breath alcohol screening test only. An ASD is a non-evidential device, meaning its result is used to decide whether a confirmation test is needed, not as the final basis for a violation determination. An STT can run screening tests for random selection, reasonable suspicion, post-accident, and return-to-duty situations, and can tell an employee whether their screening result is below 0.02, or 0.02 or higher. What an STT cannot do is administer the confirmation test that follows a screening result of 0.02 or above. That step requires a Breath Alcohol Technician operating an evidential breath testing device, so a program staffed only with STTs has a built-in dependency on BAT coverage the moment a screening result crosses the threshold.

What is a Breath Alcohol Technician authorized to do?

A Breath Alcohol Technician (BAT) is qualified under Subpart J to operate an evidential breath testing device (EBT) and can conduct both the initial screening test and, when required, the confirmation test. The confirmation test is the one that produces the result used to determine an actual alcohol violation under Part 40, so the BAT role covers the full sequence from first breath sample through a legally sufficient confirmed result. Because a BAT's device and training cover both test types, a technician holding BAT qualification can run an entire testing event start to finish without handing off to anyone else. That is the practical reason most employers who conduct their own testing, rather than sending employees to a third-party collection site, end up training at least one BAT: a screening-only STT still needs a BAT reachable whenever a screening result requires confirmation, and building in that handoff adds a step the BAT role removes.

STT vs BAT: device, test authority, and training compared

Factor	Screening Test Technician (STT)	Breath Alcohol Technician (BAT)
Device operated	Alcohol screening device (ASD), non-evidential	Evidential breath testing device (EBT)
Test types authorized	Initial screening test only	Screening test and confirmation test
Training/proficiency requirement	Qualification training plus proficiency demonstration on the specific ASD in use	Qualification training plus proficiency demonstration on the specific EBT in use
Can act as the other role?	Not automatically; cannot conduct confirmation tests without separate BAT qualification	Yes, a qualified BAT can also act as STT if proficient on the specific ASD in use

Why does the STT/BAT distinction matter for program design?

The distinction determines whether an employer needs a BAT on staff or whether STT coverage is sufficient for day-to-day screening. A program that only ever expects screening results below 0.02 can run on STT coverage, but that is a bet on outcomes, not a compliant design on its own, because Subpart N's problem-in-testing provisions require a confirmation test whenever a screening result is 0.02 or higher, and only a BAT can administer it. Employers relying solely on STTs need a documented path to BAT-administered confirmation testing, whether that is an in-house BAT on call or a contracted service that can respond within the timeframe Part 40 expects. Waiting to figure out confirmation coverage after a screening result comes back positive is the wrong time to discover the gap; it needs to be built into the written testing program before the first random selection runs.

Can a BAT also work as an STT, or is it a separate qualification?

Anyone qualified as a BAT can also act as an STT, provided they have demonstrated initial proficiency on the specific alcohol screening device the program actually uses, which is not automatic just because they are proficient on their EBT. Part 40's training standard is device-specific in both directions: qualification on one manufacturer's ASD does not carry over to a different ASD model, and EBT proficiency does not substitute for ASD proficiency. This is why employers standardizing on a single BAT for both screening and confirmation still need that person's training file to show proficiency on every device model actually deployed at each testing location, not just the EBT used for confirmation. The reverse does not work: an STT cannot function as a BAT without completing full BAT qualification training and the EBT-specific proficiency demonstration, because STT training never covers confirmation testing procedure at all.

Should an employer train BAT, STT, or both in-house?

The right mix depends on testing volume and how much confirmation risk the employer is willing to route through an outside contractor. A company running frequent random, post-accident, or reasonable-suspicion testing benefits from at least one in-house BAT, since that person covers both test types without waiting on outside coverage that may not arrive inside the window Part 40 expects for a confirmation test after a screening result. A lower-volume program can train STTs for routine screening and maintain a standing arrangement with a contracted BAT for confirmation testing, as long as that arrangement is documented and actually reachable, not a name on a policy page nobody has called in years. Employers with more than one site tend to land on training every on-site tester as a BAT rather than splitting roles, since BAT qualification covers the STT function anyway and removes the need to track two separate device-proficiency records for the same person.

How Foster handles this

Foster trains technicians as BATs rather than STT-only, so a client's on-site tester can run both the screening and, when a result requires it, the confirmation test without a handoff to a second person or a second visit. Training follows the device-specific proficiency demonstration Subpart J requires on the actual evidential breath testing device the client uses, and that proficiency record stays on file for the client's audit purposes. For employers who prefer STT-only coverage for routine screening, Foster's BAT training program can also cover the screening-only staff while establishing the confirmation-test path those STTs need under Subpart N. Programs sorting out which mix fits their testing volume can start with a quote. For background on who is qualified to run that training in the first place, see Foster's post on who can train a Breath Alcohol Technician.

Frequently asked questions

Does an employer legally need a BAT, or is an STT enough?

An STT is sufficient to run initial screening tests, but any screening result of 0.02 or higher requires a confirmation test that only a BAT can administer. An employer using STTs only still needs documented access to a BAT for confirmation testing.

Can the same person be both an STT and a BAT?

Yes. A qualified BAT can act as an STT if they have demonstrated proficiency on the specific screening device in use. An STT cannot act as a BAT without completing separate BAT qualification training.

What happens if a screening test comes back 0.02 or higher and no BAT is available?

The employer needs a documented process to get the employee to a BAT for confirmation testing without unreasonable delay, consistent with the problem-in-testing requirements in Subpart N. This is a gap to close in program design before testing starts, not after a positive screening result.

Does BAT training automatically qualify someone as an STT on any screening device?

No. Proficiency is device-specific. A BAT needs to demonstrate proficiency on the specific ASD model the program uses before acting as STT on that device, separate from their EBT proficiency.

Is a screening-only device the same thing used for confirmation testing?

No. Screening uses a non-evidential alcohol screening device (ASD), while confirmation testing requires an evidential breath testing device (EBT). They are different device classes with different qualification requirements attached.

Sources

• eCFR: 49 CFR Part 40, Subpart J, Alcohol Testing Personnel
• eCFR: 49 CFR Part 40, Subpart N, Problems in Alcohol Testing