Ignition Interlock Device: How They Work, Why They Are Used and When Are They Used
Ignition Interlock Device – This
is an instrument
that’s been designed to keep somebody who has been drinking from
operating a vehicle if the device discovers there is alcohol on the
operator’s breath. Most states have some DUI law that allows judges to
place these devices in vehicles that DUI offenders drive.
Now,
each state law on the ignition interlock device varies. So, you should
review your state’s DUI laws concerning the ignition interlock device
and if it’s a state mandate or up to the judge.

How Does The
Ignition Interlock Device Work
This
device works to get a measurement of driver’s blood alcohol content
(BAC). If the device determines that the driver has alcohol on his/her
breath, it’ll deactivate the ignition, which will keep the vehicle from
starting. It stays lock until the ignition interlock device finds
little to no alcohol on the driver’s breath. The period of lockout will
increase for each failed test.
When doing rolling retests, most
devices need a brand new fresh breath test. If, in that time period the
machine has not gotten that clean breath, an alarm will sound and the
vehicle horn will begin honking. This tells the driver to turn off the
vehicle.
The ignition interlock device will not shut off the
vehicle if the driver doesn’t pass the test especially if it’s moving.
And, some ignition interlock devices will record the information about
the repeat failed test.
Optional Ignition
Interlock Device Laws: What Judges May or May Not Do To DUI offenders
Several
states permit judges to choose if a DUI offender’s vehicle should be
equipped with an ignition interlock device after a DUI conviction,
under the DUI
criminal charge.
Some laws state that the devices may be placed on vehicles where the
person has a suspended driver’s license. For these
circumstances,
the qualified offenders must meet several other sentencing requirements
so they’ll be able to drive with it on the vehicle. These include:
- Alcohol treatment program
- Driver’s license suspension
- Fines
- Jail time
- Probation
State Ordered Ignition Interlock Devices
An increasing number of states are deciding on the issue of making ignition interlock devices mandatory rather than letting judges to decide whether or not offenders need them. The most common situations states demand the device be installed are:
- A child was in the vehicle at the time of the event
- Offenders are repeat DUI offenders
- The BAC level was extremely high
The Costs Associated With
The Ignition Interlock Device
States
have rules that lay out the terms of the device’s installation and
inspection. State approved installers must place the device in the
vehicle, which the offender must proof to the court was done.
Inspections must be done every so often by a state-approved installer.
This proof must also be sent to the court.
Yes, DUI offenders must pay fees that are associated with the ignition
interlock device. These fees include:
- Installation
- Calibrating
- Security deposit/insurance
- Payment for device
Some states will reduce the DUI fines to assist those folks who are
unable to purchase the unit.
Read about Breathalyzer Reading and how it can fail to test


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