A fuel-cell breathalyser sensor measures alcohol by electrochemically oxidising the ethanol in a breath sample, producing a small electric current that is directly proportional to the alcohol concentration. Because the reaction is specific to ethanol, fuel-cell sensors are the most accurate and reliable choice — and the standard for police and evidential testing.
Key facts
- Fuel-cell sensors generate a current proportional to breath-alcohol via electrochemical oxidation of ethanol.
- They are highly ethanol-specific, reducing false positives compared with semiconductor sensors.
- Fuel cells hold calibration well, making them the standard for police and evidential use.
How a fuel-cell sensor works
Inside the sensor, a porous electrode coated with a catalyst (typically platinum) sits between two layers. When alcohol-laden breath reaches the active electrode, the ethanol is oxidised — losing electrons — and those electrons flow through the circuit as a measurable current.
The more alcohol present, the more electrons released, and the larger the current. The device converts that current into a precise BAC reading. Crucially, the cell responds to ethanol and largely ignores other substances on the breath.
Fuel cell vs semiconductor: the difference that matters
- Specificity — fuel cells react almost exclusively to ethanol; semiconductor sensors can respond to other vapours, risking false highs.
- Stability — fuel cells drift slowly and hold calibration well; semiconductors drift faster and need recalibration more often.
- Repeatability — fuel cells give consistent results across hundreds of back-to-back tests, ideal for checkpoints and gates.
- Cost — semiconductors are cheaper, making them suitable for personal and light screening use.
Why it matters for evidential testing
When a reading may be used for enforcement, discipline or in court, it must be both accurate and defensible. Fuel-cell specificity reduces false positives, and a documented NABL-accredited calibration provides the traceability that makes the result admissible. This is why law-enforcement and workplace-compliance programs standardise on fuel-cell devices.
Getting the most from a fuel-cell device
- Recalibrate on schedule (typically every 12 months) and keep the certificate.
- Allow the recommended wait after the subject's last drink to avoid mouth-alcohol artefacts.
- Use fresh mouthpieces for hygiene and to protect the sensor.
- Store within the device's temperature range for stable readings.
Frequently asked questions
- Are fuel-cell breathalysers better than semiconductor ones?
- For accuracy, specificity and repeatability — yes. Fuel-cell sensors are preferred for professional and evidential use. Semiconductor sensors remain a good low-cost option for personal screening.
- How long does a fuel-cell sensor last?
- With proper care and scheduled recalibration, fuel-cell sensors typically remain accurate for several years before replacement.
- Do fuel-cell sensors give false positives?
- They are far less prone to interference than semiconductor sensors because they react specifically to ethanol, though correct technique and mouth-alcohol wait times still matter.