• Semiconductor Sensors: Most common in low-cost consumer devices. They use an internal tin-oxide sensor that changes electrical resistance when alcohol touches it. They are affordable but can occasionally give false positives from substances like acetone or cigarette smoke.
• Fuel Cell Sensors: The gold standard used by police and professionals. They measure alcohol through a chemical process that oxidizes the alcohol in the breath sample, generating an electrical current. The stronger the current, the higher the BAC. They are highly accurate and specific to alcohol.