The use of alcohol breathe analysers to immobilise a car if the driver is over the limit is becoming accepted. In Sweden, workers can be obligated to use the measuring devices as part of an employment contract.
Some areas in Australia and Canada have introduced requirements on people convicted of a drink driving offence to have the instruments installed in their cars before their licence is reinstated.
Methods of detection are based on Non Dispersive infra-red spectroscopy. Breathe from the subject is passed through a meas-urement cell where a broadband IR source is used to emit light through the cell to a detector. The detector uses IR optical filters to filter the light into an active channel at the absorption wavelength of the target gas and a reference channel. In simple terms, the light intensity at the detector decreases as the alcohol concentration in the chamber increases.
In order to measure gases at particularly small concentrations or very quickly a high sensitivity detector is required. The L220X1810 manufactured by LASER COMPONENTS is a dual channel, current mode sensor with a responsivity of 120,000 V/W. The device is housed in a standard T0-39, 4 pin package. They have long expected lifetimes making them ideal for this fit and forget application.
