Fuel-cell vs semiconductor sensors: choosing on evidence, not marketing
Both sensor types measure breath alcohol, but they fail in different ways. The right choice depends on test volume, the consequence of a false positive, and your calibration budget.
How each sensor works
An electrochemical fuel-cell sensor oxidises ethanol at an electrode and measures the resulting current, which is proportional to the alcohol present. A semiconductor (metal-oxide) sensor measures a change in the resistance of a heated tin-dioxide film when it encounters reducing gases.
The consequence is selectivity. The fuel cell responds to ethanol specifically; the semiconductor responds to a family of substances, which can include acetone, some solvents, tobacco smoke residues and certain foods. That is the single most important practical difference.
Where each one belongs
Fuel-cell devices hold accuracy better across repeated tests and drift more slowly, which suits gate testing, fleets and any programme where a positive result triggers a consequence for the person tested. Semiconductor devices are cheaper and useful for indicative awareness checks, personal use and low-volume screening where a re-test on a fuel-cell device is available.
- High test volume or disciplinary consequence → fuel cell.
- Awareness, self-checks or occasional screening → semiconductor is usually sufficient.
- Mixed programme → fuel-cell device at the gate, semiconductor units on the floor.
Standards to ask about
For breath alcohol screening devices, the international reference points most often cited are OIML R 126 (evidential breath analysers) and the European EN 15964 / EN 16280 series for professional and personal devices. Ask any supplier which standard a device was tested against, by whom, and for which model revision — then ask for the document.
Calibration is part of the choice
A sensor's accuracy claim is only meaningful within its calibration interval. Fuel-cell devices typically hold calibration longer but cost more to service; semiconductor devices are cheaper to replace than to maintain. Budget the whole life of the device, not the purchase price.