Sometimes, when you try to blow into a personal breathalyzer before driving, you run out of breath before the prompt ends or the test does not complete. Especially at times like the morning after a company dinner, when you want to decide quickly whether to drive, it is easy to keep repeating it, thinking "maybe if I just blow a bit harder." But if not enough breath sample went in and the test procedure did not finish, the device has not told you whether alcohol is present or what the reading is.
A personal breathalyzer is a device that shows a reference reading based on exhaled breath. For example, the AF-40BT can be used on its own or linked to a smartphone app, and a user manual is included with the product. However, breath volume and how a test is completed should follow the instructions for each model. If you find it hard to blow all the way through, it is safer to clearly note that the test was incomplete and to handle the driving decision and the device-use issue separately, rather than forcing repeated attempts.
An incomplete test is not a "low result"
If no reading appeared on the screen or the test stopped partway, you cannot take that to mean there is no alcohol. All you can know is whether the breath was insufficient, at which stage the procedure stopped, and what wording or symbols appeared on the screen. If you reinterpret an incomplete test as if it were a negative result, you lose the basis for deciding whether to drive.
When you are short of breath or find it hard to exhale steadily through your mouth, there is no need for pressure to blow longer or harder. If repeated attempts themselves are uncomfortable, stop at that point and change your travel plan: rather than waiting for a completed test, first consider other options such as public transportation, a taxi, a designated driver service, or riding with someone else.
The first things to note are the screen and the stage of use
To get support from the manufacturer, what actually happened matters more than saying "it doesn't work." In particular, even devices that look similar can differ in test method and screen display, so do not borrow another model's explanation to decide what an error means. For a product that comes with a manual, such as the AF-40BT, you can first compare the procedure and guidance in that manual.
| What to organize | What to note | Why it helps with the next step |
|---|---|---|
| Product identification | The exact product name on the device | To find the right manual and support procedure |
| The moment it stopped | Whether it was at the ready, start, or breath-in-progress stage | It distinguishes the situation better than saying there was no number |
| Screen display | Wording, numbers, and symbols exactly as shown | You can pass on the actual prompt instead of a guessed error name |
| Attempts already made | Whether you checked the manual and how many times you tried | It keeps you from forcing the same action again and again |
If possible, note what was displayed before the screen disappears. If you were using the app link, look separately at the completed test records left in the app and the times when there were incomplete attempts. Just because a record exists, you should not treat failed attempts as valid tests.
How to separate decisions in a hypothetical situation
Suppose a driver tried to test with an AF-40BT the morning after a gathering, but could not keep breathing out and no result appeared on the screen. The fact to observe is that "the test did not finish while breath was being given and no number was displayed." From this, you cannot immediately interpret it as "I've sobered up completely" or "the device is broken."
A possible action is to write down the product name on the device, the stage where it stopped, and the screen display, compare them with the relevant guidance in the user manual, and pass them on to the manufacturer's support if needed. If it is time to drive, settle on another way to travel rather than putting off the decision while waiting to see whether a test succeeds. The completion criterion in this situation is not forcing out a reading, but switching the driving plan to a safe alternative and having reproducible information ready for the device inquiry.
How far family or colleagues can help
People nearby can help by finding the manual, writing down the wording on the screen, and organizing the information needed for a support inquiry. On the other hand, having someone else blow and using that result as your own does not help. That reading cannot show the condition of the person who actually intends to drive.
It is also better to avoid urging someone who has difficulty breathing to keep trying. Whether the discomfort is due to a temporary condition, the device procedure, or a health-related issue cannot be judged from a failed test alone. If you are worried about health discomfort or symptoms, consider appropriate medical help separately from the device inquiry, and do not use the device's reading or incomplete status as a basis for health judgments.
Write test records in a way that does not hide failures
Even with a product that can store test results in the app or device memory, the purpose of the records is not to calculate when you can drive. You can use them to look back at when you attempted tests and which results were completed, and to notice patterns where you left too little margin in the next day's driving schedule. When sharing records with family, it is also best to agree on the scope and purpose of sharing in advance.
On a day when you could not blow all the way through, record the very fact that there was no completed reading. Do not fill that blank with an estimate, decide on your next trip conservatively, and check the device issue through the model-specific instructions. Separating things this way reduces the chance that trying to force a fix for a failed test makes your driving decision uncertain as well.
※ Self-check results from our products are provided as reference information only. Actual enforcement standards and test methods may differ by agency and equipment, so self-check results and enforcement results may differ, and the company accepts no responsibility for enforcement results.
