Remove sources of error first
Wait after alcohol, food and anything else that remains in the mouth
Immediately after drinking, alcohol remains in the mouth at a much higher concentration than in deep-lung breath. It can temporarily raise the reading. Measurement procedures commonly specify an observation period of about 15–20 minutes with no drinking, eating, smoking, vaping, chewing gum or mouthwash. Check the exact interval in the instructions.
If you burp, vomit or use a product containing alcohol during that period, start the interval again. Test in a calm place, away from alcohol fumes, solvents and heavily used disinfectants.
Four steps
Measurement step by step
Prepare the device
Check the battery, mouthpiece, messages and warm-up time.
Blow steadily
Use a new mouthpiece and blow continuously for as long as the device instructs.
Read the unit
Do not compare mg/L with per mille without the appropriate conversion for that system.
Confirm the result
Repeat the test after the manufacturer's specified interval and compare the readings.
A number without a unit is incomplete
0.20 mg/L is not the same as 0.20‰
Breathalyzers may display, among other units, mg/L of alcohol in breath, ‰, g/L or % BAC. Always look at the small symbol next to the number. Do not change units by guesswork and do not use one universal conversion for every country — legal definitions and accepted conversion factors may differ.
Cheers · forecast and measurement
Two tools, two different roles
Cheers helps you plan an estimated return to zero. A breathalyzer measures a sample here and now. Use the forecast for planning and the measurement for checking.
What most often spoils a reading
A result can be false for more reasons than alcohol in the mouth
Testing too soon
Food, alcohol, a cigarette or mouthwash immediately before testing disrupt the conditions.
Breath too short
Stopping early may produce a sample error or a result that cannot be compared with the next one.
Wrong unit
The same number in mg/L and per mille describes entirely different concentrations.
No calibration
Sensors drift over time. The service interval depends on the model and number of tests.
A breathalyzer needs care too
Calibration, mouthpieces and storage determine reliability
Record the date of the last calibration and the number of tests if the manufacturer specifies a limit. Do not store the device in a hot car or severe cold. Use a clean mouthpiece for each person, and do not blow smoke or vapour from an alcohol-containing product into the sensor.
