Patent ID: 7204335

Claim:
A sobriety interlock device having an output coupled to a starter mechanism of a motorized vehicle for detecting the presence of alcohol in a breath sample introduced into the device and for controlling the device output in response to a predetermined threshold level being exceeded, the sobriety interlock device comprising: a) a handset having a gas intake channel for receiving the breath sample, b) a breath sampling housing enclosed within the handset and having a gas sampling channel in axial alignment with the handset gas intake channel, c) a fuel cell positioned along the gas sampling channel of the breath sampling housing for measuring an alcohol vapor value of the breath sample, d) a pressure transducer located within the handset in fluid communication with the gas sampling channel of the breath sampling housing for measuring a pressure value of the breath sample, e) a microprocessor located within the handset in electrical communication with the fuel cell and the pressure transducer, the microprocessor containing an executable algorithm for determining a measured blood alcohol content of the breath sample through an offset adjustment of the measured alcohol vapor value in relation to the measured breath sample pressure value, the microprocessor applying a signal to the output of the interlock device dependent on the results of the measured blood alcohol content as compared to the predetermined threshold level; f) a solenoid valve positioned upstream from the fuel cell along the gas sampling channel of the breath sampling housing for limiting the size of the breath sample across the fuel cell by opening for a finite period of time, the solenoid valve having a normally open state; and g) a power source coupled to the handset.