When you store or review breath alcohol test results, the 0 on the screen is the number most easily over-interpreted. Safety managers and quality or technical staff need to distinguish whether this value is a zero displayed after a normal breath analysis, the starting value of the range the device can display, or a case where no result was left during testing or transmission. Especially in setups that move results from the device screen to a smartphone app or a server, the number 0 and an empty result can look the same.
A zero result means a reading that the device displayed as 0 after the analysis was completed. A detection limit, by contrast, is the lowest level that has been documented, under defined test conditions, as distinguishable between the measurement signal and background variation. Only by separating these two concepts can you treat the number 0 as an actual result without concluding from that number alone anything about the device's performance or the cause of a missing record.
The start of the display range and the detection limit are different
DATECH's official product information for the AF-40BT gives the display range as 0.000–0.500 %BAC, 0.00–5.00 ‰, and 0.00–2.50 mg/L. Here, %BAC, ‰, and mg/L are the concentration display units the product uses to show results, and the range is the interval of values that can be displayed in each unit. So the fact that 0 is the starting value of the display range does not mean every tiny difference above 0 can be distinguished.
The detection limit is also different from the number of displayed digits. For example, seeing three decimal places as in 0.000 does not mean a detection limit has been established down to differences at the last digit. The public product information for the AF-40BT gives the display range and accuracy, but no separate detection limit figure can be found, so you must not assign a particular detection limit based on the zero display alone.
Separate the scope that an accuracy figure answers
Accuracy is information showing how far a reading can differ from a reference value under test conditions that have a reference value. The AF-40BT states accuracy of ±0.005 %BAC at 0.100 %BAC, ±0.05 ‰ at 1.00 ‰, and ±0.025 mg/L at 0.50 mg/L, at 25 ℃. This is performance information at each reference concentration and temperature; it does not mean the detection limit near zero or the range of results in every environment.
When you review a zero on the screen, it is important not to use the display range, accuracy, and detection limit in place of one another. The display range is the interval the screen can express, accuracy is the difference compared with a reference value under specific conditions, and the detection limit is a test criterion for distinguishing low-level signals. If a report requires you to state a detection limit, the right approach is to obtain a manufacturer document that states the limit together with its test conditions, rather than copying over the display range or accuracy values.
Record whether analysis was completed before the concentration value
In test data, a zero and "no result" must not be turned into the same value. A record where analysis finished normally and 0 was displayed and a record where the breath sample was not analyzed, or analysis stopped before finishing, call for different follow-up reviews. If 0 is filled in automatically because a value is empty, the meaning of the zero rate, the average, and the count of missing records are all distorted.
| What to distinguish | Information to keep on screen or in the stored record | Why distinguish it |
|---|---|---|
| Whether the breath sample was accepted for analysis | Whether the sample was accepted for analysis | So that an unanalyzed sample is not turned into a concentration of 0 |
| Whether the analysis finished | Whether analysis was completed and when | So that incomplete records can be excluded from zero counts |
| The device's original display | The original value and original unit | So the first result can be traced even after conversion or integration |
| Whether a detection limit is documented | Whether there is a manufacturer document including test conditions and units | So that an unconfirmed limit is not attached to results |
Apply this distinction within the information the device and integration software actually provide. The AF-40BT advertises storage of 10,000 test results and Bluetooth smartphone pairing, but the public product information alone does not tell you whether each stored record includes analysis completion status or transmission status. Rather than having the server guess at a status that is not provided and create a new field, it better preserves the meaning of the data to show separately that this information cannot be confirmed.
Processing order in a hypothetical integration case
As a hypothetical example, suppose a worksite collects AF-40BT results on a management screen via a smartphone app. One record shows 0.000 %BAC, and another has only the test time with an empty value field. The first things to observe are each record's original unit, test time, whether the app received a result, and whether there is any indication distinguishing completed analysis from transmission failure.
The first record may be a result that the device displayed as zero after analysis was completed. However, the second record may not be a concentration of 0 but a record where the result was not delivered or where there is no information to confirm the result, and the public product information gives no basis for interpreting it as zero. Possible actions include checking whether the app and server automatically fill empty values with 0, and designing the display so that zero values and results not received are shown with different labels or statuses.
The criterion for considering the action complete is that when you load test records made under the same conditions, normal zero results and records without values are not merged into the same value. Even when a report purpose requires a detection limit, do not estimate the limit from zero values. Link a limit to the records only when you have confirmed the limit, unit, and test conditions together in the manufacturer's test documents and that information exists.
Give the number 0 only as much meaning as it needs
The starting point is to interpret a zero within the scope of being a result the device displayed as 0 after a normal analysis finished. You cannot draw conclusions about the detection limit, the quality of the breath sample, and whether communication succeeded all from this one number. Conversely, there is no reason to treat a zero result itself as an error or an empty value.
On the operating screen, it is appropriate to handle zero values, incomplete analysis, results not received, and unconfirmed detection limits as separate statuses. Dividing them this way lets you use only normally completed results when analyzing the zero rate, and review records without values separately when looking for the cause of omissions. Keeping the meaning of the number 0 narrow and clear is the basis for interpreting both device results and integrated data technically.
