What You Need to Know about Ignition Interlock Devices

Any driver who is found guilty of driving under the influence of alcohol (DUI) or driving while intoxicated (DWI) faces strict penalties. Some drivers, particularly those who are convicted of a second or later offense in New Hampshire, may be required to have an ignition interlock device installed on their vehicle.

Put simply, an ignition interlock device is a breath testing machine connected to the car’s ignition. The testing machine generally consists of a tube connected to a sensor. Most ignition interlock devices identify alcohol by using an ethanol-specific fuel cell. The cell is covered by a thin layer of platinum, which oxidizes when it comes in contact with alcohol molecules. The machine also contains a sensor that scans for the specific kind of oxidization that occurs when the cell comes in contact with alcohol. If the sensor “sees” this type of oxidization, it sends a signal to the car’s ignition to prevent it from starting. The machine may also make an entry in the device’s computer memory, which can be downloaded later.

The fuel cell technology used in most ignition interlock devices is different from the technology used in most breath testing machines, which typically use infrared spectroscopy to “see” alcohol molecules in a breath sample. Although the fuel cell doesn’t usually give an accurate reading of the amount of alcohol in a breath sample, it is usually accurate at determining whether any alcohol is present or not. Fuel cells are also considerably cheaper than infrared spectroscopy. Since the driver convicted of DUI usually has to pay the cost of installing the ignition interlock device, price matters.

This blog post appears courtesy of Tenn And Tenn, P.A., a New Hampshire based law firm that handles NH DWI cases.

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