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Ignition Interlock FAQs

What is an ignition interlock?

An ignition interlock device (IID) is a breath alcohol analysis device that is installed in a motor vehicle.  The Interlock prevents a driver from starting a vehicle if the driver’s breath alcohol concentration (BrAC) is above a pre-set fail level.  If the BrAC is under the pre-set fail level, the IID will allow the ignition of the vehicle to start the engine. 


If a valid breath sample is not provided, or if the BrAC is at or above the pre-set fail level, the ignition will be disabled thus preventing the engine from being started.  The Interlock system records a variety of information including dates, times, test results, engine runs and engine offs.  This data is provided to designated authorities and used to determine compliance with the respective Interlock program.

How does it work?

The device will be activated once the key has been put into the vehicle’s ignition and turned on.  The device will prompt the driver to blow into the device to provide a breath sample.
If the breath alcohol concentration (BrAC) analyzed in the breath sample is below the pre-set fail level the engine can be started.   If the BrAC is at or above the pre-set fail level, the ignition will be disabled and the vehicle will not start.  The IID will “Lockout” for a short period of time. 


Once this period has expired, another breath sample can be provided. At random times during vehicle operation, the IID will prompt the driver to provide another breath sample or a running retest.  If the breath sample for the retest is failed or missed, the IID will log the event as a violation, warn the driver and in some cases start up an alarm (e.g. lights flashing, horn honking, etc.) until the ignition is turned off, or a valid breath sample is provided.


What is the process of having the IID installed, monitored and removed?

Installation:  Once an individual has an IID restriction, an appointment is scheduled with a service center for installation of the IID.  At the initial installation, the participant will be trained on how to use the device and the applicable program requirements. 

Monitoring:  The IID will need be monitored regularly (usually once a month or every two months) so that the IID data can be uploaded, and the device can be calibrated. 

Removal:  Once the order has been issued removing the IID restriction, the participant can then schedule a removal appointment.

How much does it cost?

Every state and IID manufacturer have different prices, but they range anywhere from $65-$100 per month.  However, additional fees may apply for installation, calibrations, maintenance or violations.

What are the benefits?

Most importantly is keeping intoxicated drivers from operating a motor vehicle.  For DUI offenders an IID allows the participant to retain their driving privileges for the duration of their probation.   IIDs can be voluntary as well, which can result in reduced insurance costs.

Can I bypass the device?

IIDs are able to detect if an air pump or filter is being used to provide the sample.  A violation would be recorded at that time.

What if the vehicle stalls in traffic?

The IID will allow the ignition to be restarted without providing a breath test for a couple minutes following the engine’s cease of operation.  This will allow the driver a sufficient amount of time to quickly restart the engine.

Will the unit shut off the engine?

No.  An IID does not shut off a vehicle’s engine or stop it abruptly in its tracks.  If a retest is failed or if the retest is not presented when required, a violation will be recorded and the vehicle’s horn may sound and the lights may flash until either the breath test is passed or the vehicle is turned off by the driver.


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