Patent ID: 8455262

Claim:
A method to avert an unlawfully intoxicated driver from operating a vehicle comprising: utilizing a passive ethanol vapor sensor configured to measure ethanol vapor concentration in air from a vehicle cabin; passing vehicle cabin air, including sample ethanol vapor, through an adsorber; measuring an output (designated V off ) of an infrared detector, with an infrared source deactivated; heating the adsorber; measuring an output (designated V on ) of the infrared detector, with the infrared source activated; passing concentrated sample ethanol vapor from the adsorber into and through an infrared absorption cell at a predetermined time; measuring a change in an output (designated V sig ) of the infrared detector; and calculating a ratio V sig /(V on −V off ), wherein the ratio V sig /(V on −V off ) is indicative of the ethanol vapor concentration in the vehicle cabin air; and imposing a safety response when the passive ethanol vapor sensor detects that a sample of vehicle cabin air indicates that a vehicle occupant exceeds a legal blood alcohol concentration (BAC) for a driver.