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IID Technology

If you have been convicted for Driving Under the Influence (DUI), or Driving While Intoxicated (DWI) in California, you may be required by the court to install an Ignition Interlock Device or IID on any vehicles you own or operate for a maximum of three years from the date of the conviction (California Vehicle Code Section 23575).

Ignition interlock devices are attached to a vehicle's steering column and sealed with tamper-proof tape. The driver must use a special breathing technique intended to prevent others from taking the test. It is a crime in California to tamper with an ignition interlock device (California Vehicle Code Section 23247 - Ignition Interlock Device Prohibitions), or to blow into the tube to start the vehicle for another driver.

The devices are similar to breathalyzer used by California police - the driver breathes into a tube, and the device determines his or her breath alcohol content (BAC). Some devices are set to allow a relatively low BAC that is far below the legal limit for driving. Often the device is set to prevent the vehicle from starting if the driver has consumed any alcohol at all.

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Once the vehicle is in motion, "rolling re-tests" are required during specified periods to keep the engine running. Rolling retests are intended to ensure that the driver, not another party, is the person who provided the alcohol-free breath test that started the car. The device keeps a record of each test, as well as any attempts to tamper with the equipment. A common misconception is that ignition interlock device will simply turn off the engine if alcohol is detected; this would, however, create an unsafe driving situation and expose interlock manufacturers to considerable liability.

Modern ignition interlock devices use an ethanol-specific fuel cell for a sensor. A fuel cell sensor is an electrochemical device in which alcohol undergoes a chemical oxidation reaction at a catalytic electrode surface to generate an electrical current. This current is then measured and converted to an alcohol equivalent reading. Although fuel cell technology is not as accurate or reliable as infrared spectroscopy technology used in evidentiary breathalyzers, they are cheaper and tend to be more specific for alcohol.

The devices keep a record of the activity on the device and the interlocked vehicle's electrical system. This record, or log, is printed out or downloaded each time the device's sensors are calibrated, commonly at 30, or 60 day intervals. Authorities may require periodic review of the log. If violations are detected, then additional sanctions can be implemented.

Periodic calibration is performed using either a pressurized alcohol/gas mixture at a known alcohol concentration, or with an alcohol wet bath arrangement that contains a known alcohol solution. The costs of installation, maintenance and calibration are generally paid by the offender, and typically are about $75 per month.

Ignition interlock devices were once up to the discretion of the court in multiple-DUI cases, but they are now mandatory. Judges can also order the device installed in first-time driving under the influence cases. Some judges order the device to be installed in any first-time DUI case where the driver had a BAC of .10 percent or greater.

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