Patent ID: 7736903

Claim:
A chemical vapor sensor that compensates for environmental variations comprising: an infrared source for generating infrared waves; an infrared detector for measuring an intensity of the infrared waves generated from the infrared source; a vapor concentrator including a vapor adsorber and a heating source to heat the vapor adsorber, for concentrating vapor from a sample volume of air, wherein the concentrated vapor is passed into a path of the infrared waves; a sampling intake for passively acquiring the sample volume of air and passing the sample volume of air to the vapor concentrator; wherein a suspect vapor, a first tracer vapor and a second tracer vapor are measured from the sample volume of air and the sample volume of air is sampled from a motor vehicle cabin, and the suspect vapor is ethanol vapor from a person's exhaled respiration, the first tracer vapor is carbon dioxide from the person's exhaled respiration, and the second tracer vapor is carbon dioxide from ambient air from the motor vehicle; and a processor configured to calculate an adjusted suspect vapor measurement utilizing the suspect vapor, the first tracer vapor measurement and the second tracer vapor measurement, wherein the processor calculates the adjusted suspect vapor measurement by calculating a product of the ethanol suspect vapor measured and carbon dioxide tracer typically in a person's exhaled respiration, divided by a difference of the carbon dioxide first tracer vapor measured and the carbon dioxide second tracer vapor measured from ambient air.