An alcometer — also called a breathalyser or breath alcohol tester — is a device that estimates a person's Blood Alcohol Concentration (BAC) from a breath sample. As you exhale, alcohol crosses from your blood into the air in your lungs at a fixed ratio, so a breath reading reliably reflects how much alcohol is in your bloodstream.
Key facts
- An alcometer measures BAC from deep-lung breath using a fixed blood-to-breath ratio (commonly 2100:1).
- Fuel-cell sensors are the most accurate and ethanol-specific; semiconductor sensors are cheaper screeners.
- Accuracy is only defensible when the device carries a valid NABL-accredited calibration certificate.
How an alcometer works
When you drink, alcohol is absorbed into your blood and carried to your lungs. There, a known and stable proportion of it evaporates into the air in the tiny air sacs (alveoli). An alcometer samples this deep-lung 'alveolar' air and converts the alcohol it detects into a BAC estimate, usually shown as a percentage (e.g. 0.03% BAC) or in mg/100 ml.
Professional devices wait for a deep-lung sample and apply a fixed blood-to-breath ratio (commonly 2100:1) so the breath figure maps consistently to a blood figure.
The two main sensor technologies
- Fuel-cell (electrochemical) sensors — react alcohol electrochemically to produce a current proportional to alcohol concentration. They are highly specific to ethanol, stable over time, and are the choice for police, evidential and high-volume professional use.
- Semiconductor (MOS) sensors — a heated metal-oxide film changes resistance in the presence of alcohol. They are lower cost and fine for personal and screening use, but less specific and need more frequent calibration.
Where alcometers are used
- Law enforcement — roadside DUI/drink-driving checkpoints, with printed evidential records.
- Fleet & transport — pre-trip driver screening for logistics, cabs and buses.
- Manufacturing & construction — gate-entry and pre-shift screening on safety-critical sites.
- Healthcare — de-addiction monitoring, occupational health and emergency assessment.
- Corporate & events — HR alcohol-policy enforcement and venue compliance.
Key benefits
Breath testing is non-invasive, fast (results in seconds), and gives an immediate, on-the-spot number with no needles or lab wait. With a fuel-cell sensor and NABL-accredited calibration, the result is accurate and defensible — meaning it can stand up in audits, HR proceedings and court.
How to choose the right alcometer
- Use case & volume — occasional personal checks vs. hundreds of roadside or gate tests a day.
- Sensor — fuel cell for accuracy and evidential needs; semiconductor for budget screening.
- Records — choose a printer or app-logging model if you need an audit trail.
- Calibration — insist on a NABL-accredited certificate and an annual recalibration plan.
Frequently asked questions
- Is an alcometer the same as a breathalyser?
- Yes. 'Alcometer', 'breathalyser', 'breath analyser' and 'alcohol tester' all refer to a device that estimates BAC from a breath sample.
- How accurate are alcometers?
- A well-maintained, calibrated fuel-cell device is accurate to roughly ±0.01% BAC. Accuracy depends on the sensor type and on keeping calibration current.
- Do alcometers need calibration?
- Yes. Sensors drift over time, so devices must be recalibrated periodically — typically every 12 months — to stay accurate and legally defensible.