A BAC tester turns a breath into a number that estimates how much alcohol is in your blood. That number looks precise on the screen, yet it carries a margin, it depends on the sensor and its calibration, and it can be thrown off by how soon you blow after a drink. This page explains how to read a BAC result, what a stated tolerance really promises, and which testers have makers who publish the figures you need to judge them. Model details come from the manufacturer's published specifications and public documentation.
BACtrack Trace Professional, a slim fuel cell handheld rated at plus or minus 0.005 at 0.050% BAC by its maker.
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BACtrack S80, a Pro Grade fuel cell unit with a stated tolerance at 0.100% BAC and about 1,500 tests per set of batteries.
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BACtrack Mobile, a pocket fuel cell tester that reports to a phone app with a test history and a time to zero estimate.
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AlcoMate Revo, a professional fuel cell tester whose owner swaps a precalibrated module instead of waiting for a service return.
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A breath tester does not reach your blood. It measures alcohol in the air from deep in your lungs and converts that to an estimated blood alcohol concentration using a fixed ratio. In the US the result is usually shown as percent BAC, which equals grams of alcohol per 100 milliliters of blood, so 0.080 means 0.08 grams per deciliter. Some professional instruments report breath alcohol in milligrams per liter instead; the Draeger Alcotest 5820, for example, lists a range of 0 to 2.5 mg/L.
Because the conversion assumes an average person, your own result can sit a little above or below your true blood level even when the device itself works perfectly. Body temperature, breathing pattern and recent drinking all shift the breath reading.
This is an estimate. It cannot tell you whether you are safe or legal to drive. If you have been drinking, do not drive.
For the full background on the number itself, read our page on blood alcohol concentration.
Makers that publish accuracy usually give one tolerance at one test level, for example plus or minus 0.005 at 0.050% BAC. In plain terms, when the true level is 0.050 the device should show something between 0.045 and 0.055. The figure says nothing certain about readings far from that point, and it only holds while the sensor is in calibration.
Our guide on how accurate are breathalyzers explains the other factors that move a result.
| Model | Sensor | Stated accuracy | Calibration | Best for |
|---|---|---|---|---|
| BACtrack Trace Professional | Fuel cell (Xtend) | Plus or minus 0.005 at 0.050% BAC | Send-in service, at least yearly per maker guidance | Slim pro-grade checks |
| BACtrack S80 | Fuel cell (Xtend) | Plus or minus 0.005 at 0.100% BAC | Send-in service, at least yearly per maker guidance | Frequent household use |
| BACtrack Mobile | Fuel cell (Xtend) | Plus or minus 0.005 at 0.050% BAC | Send-in service, every 6 to 12 months per user guide | App history and trends |
| AlcoMate Revo | Fuel cell, swappable module | Plus or minus 0.005 at 0.10% BAC | New module every 1,000 tests or yearly | Workplace and heavy use |
Who it suits: a buyer who cares most about precision near lower BAC levels and wants a flat unit that fits a pocket.
What to know: it has an LCD but no app, and the maker does not publish how many decimal places it shows. The bactrack trace professional breathalyzer review covers it in depth.
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Who it suits: a family that shares one tester and wants it to last through many tests between battery changes.
What to know: its tolerance is quoted at 0.100, a higher point than the Trace figure. See the bactrack s80 review.
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Who it suits: someone who wants every result saved with a time stamp and likes the estimate of when BAC returns to 0.00%.
What to know: the tester is useless without a charged phone nearby, and the maker sells it today as BACtrack Mobile while some pages still call it Mobile Pro. Read the bactrack mobile pro review.
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Who it suits: an employer or program that tests many people and needs the device back in use the same day after maintenance.
What to know: the maker states DOT approval, which we could not match to an entry on the federal conforming products list, and the modules are an ongoing cost. Details in the alcomate revo review.
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Decide first whether you need a trend or a single number. If you want to learn how your body handles drinks over time, consistency matters more than the last decimal, so a fuel cell tester with an app log is a sensible choice. If you need the closest possible number at low levels, favor a unit whose tolerance is stated at 0.050.
Then think about upkeep. A BAC tester is only as good as its last calibration, so check how the maker handles service and set a reminder. The fuel cell breathalyzer category lists the models whose makers document a calibration path, and our bac calculator helps you understand the numbers before you buy a device.
It means the device detected no alcohol above its threshold in that breath, within its stated margin and only if it is in calibration.
Different sensors, calibration dates, tolerances and blowing technique all move the result, so small gaps between devices are normal.
No, police evidential instruments follow formal procedures and certification, while home BAC testers are screening devices.
No, the range shows the levels a device can report, while accuracy is a separate figure stated at a specific BAC level.
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