“Quant only” on a breath alcohol test result means the result is being reported as a quantitative number only — a reading like 0.000 or 0.024 — with no pass or fail label attached. It is the normal reporting format for breath alcohol tests, not a sign that something went wrong with the test or the device. The number is the result; someone else decides what it means.
What “Quant Only” Means on Your Result
Breath alcohol tests used in workplace and Department of Transportation (DOT) screening programs do not label results “positive” or “negative” the way a drug panel might. The device measures the alcohol concentration in your breath, converts it to the standard blood-alcohol-equivalent format, and reports that number by itself. Reporting systems typically display this as “Quantitative Only” or “Withheld.”
That label is not an error, an incomplete test, or a flag that the sample was bad. It just means the instrument’s job is to produce the number, and the pass/fail judgment lives somewhere else. A result of 0.000 means no alcohol was detected. Any higher number is handed off to be compared against the applicable cutoff.
Who Decides Pass or Fail, and at What Number
The person who turns your quant number into a consequence is usually your employer’s designated employer representative (DER), a medical review officer (MRO), or whoever your company’s substance abuse policy names. They compare the number against the threshold that applies to you.
If your test was DOT-regulated — trucking, pipeline, transit, aviation, rail, or maritime — two numbers matter:
- A result below 0.02 is treated as negative. Nothing further happens.
- A result of 0.02 through 0.039 triggers temporary removal from safety-sensitive duties. You cannot return to that work until either a retest comes back under 0.02 or at least eight hours have passed since the original test, whichever comes first.1eCFR. 49 CFR Part 199 – Drug and Alcohol Testing
- A result of 0.04 or above is a violation on par with a positive drug test. It means mandatory removal from safety-sensitive duties and referral to a substance abuse professional.1eCFR. 49 CFR Part 199 – Drug and Alcohol Testing
Non-DOT workplaces write their own rules. Many private employers pick their own cutoff, and some run zero-tolerance policies where any detectable alcohol triggers discipline. Your employee handbook or substance abuse policy will spell out the number that applies to you. The “quant only” label does not change any of those thresholds. It is just the format the number arrived in.
Screening vs. Confirmation Numbers
DOT alcohol testing happens in two stages, and only one of the numbers on your paperwork is the official one.
The first stage is a screening test. It can use an evidential breath testing device (EBT), a non-evidential breath device, or a saliva-based alcohol screening device.2eCFR. 49 CFR Part 40 Subpart L – Alcohol Screening Tests If the screening comes back below 0.02, the test is complete and negative. No confirmation needed.
If the screening is 0.02 or higher, a confirmation test has to follow. The confirmation must use an EBT specifically, and it must happen at least 15 minutes but no more than 30 minutes after the screening ends. During that wait, the technician must tell you not to eat, drink, put anything in your mouth, or belch, and must explain that the wait exists to protect the accuracy of your result.3U.S. Department of Transportation. DOT Rule 49 CFR Part 40 Section 40.251
Only the confirmation number counts. If the confirmation comes back below 0.02, the test is recorded as negative regardless of what the screening showed. So if you are staring at two different quant numbers on your form, the one that matters is the confirmation reading.
When the Number Might Overstate Your Actual Level
A quant number that looks higher than it should can reflect what you actually had in your system. It can also reflect a handful of well-documented interference problems.
Mouth Alcohol
Breath tests are designed to measure alcohol from deep in the lungs, not residue sitting in your mouth or throat. Recent drinking, belching, vomiting, mouthwash, cough syrup, and some breath sprays can leave alcohol in the oral cavity that the device reads and adds to the number. The 15-minute wait before a confirmation test, with continuous monitoring, is there to prevent this.3U.S. Department of Transportation. DOT Rule 49 CFR Part 40 Section 40.251
Modern devices also use slope detectors — algorithms that watch the concentration curve during your exhalation. Infrared instruments watch for unusual waviness; fuel-cell devices may use duplicate sensors and flag the sample when the two readings diverge beyond a set threshold.4National Library of Medicine. The Limitations of Mouth Alcohol Detection Systems in Breath Alcohol Testing The same research notes these safeguards have recognized limitations.
Acid Reflux and GERD
Gastroesophageal reflux disease can carry small amounts of ethanol vapor from the stomach up into the airway, where it gets measured alongside the alcohol already in your breath. No current breath device can tell the two sources apart. The result is a reading that looks legitimate but is inflated. GERD affects roughly 20% of adults, so this is not a rare edge case.
Diabetic Ketoacidosis
People in diabetic ketoacidosis produce elevated acetone and isopropanol as their body breaks down fat. Some breath devices, particularly older electrochemical models, can mistake those compounds for ethanol. In one documented case, a driver with severe metabolic ketoacidosis tested positive on an electrochemical screening device despite having no ethanol in his blood at all; a dual-wavelength infrared analyzer correctly identified the substance as an interferent.5PubMed. Biotransformation of Acetone to Isopropanol Observed in a Motorist Involved in a Sobriety Check
Calibration and Operator Issues
Breath devices need regular calibration against known reference samples. Skipped maintenance, expired calibration certifications, or departures from the manufacturer’s procedure can produce unreliable numbers. Operator technique matters too: a reused mouthpiece, the wrong sequence of steps, or sloppy recordkeeping can compromise a test. Calibration logs and maintenance records are discoverable in legal proceedings, and gaps in those records are among the most common grounds for challenging a result.
Challenging the Number
If you think your quant result is wrong, start by requesting the full testing paperwork: the Alcohol Testing Form (ATF), the device’s calibration history, and the technician’s certification records. These are the documents that reveal procedural problems.
Common grounds for a challenge include a missed or shortened 15-minute waiting period, missing or expired calibration records, operator certification gaps, and documented medical conditions like GERD or diabetes that are known to produce inflated readings. In DOT testing, if the 15-minute wait was not observed, or if the confirmation test began more than 30 minutes after the screening, the technician must document the deviation and the reason. Starting the confirmation late does not automatically invalidate the test, but it may be a regulatory violation and can strengthen a challenge.3U.S. Department of Transportation. DOT Rule 49 CFR Part 40 Section 40.251
Your employer’s substance abuse policy should describe the internal process for disputing a result. If the number is going to cost you your job or your safety-sensitive certification, the time to raise medical conditions, procedural problems, or calibration gaps is as soon as you see the result, before the record hardens.