All About Ignition Interlocks

Prevent Drunk Driving with an Ignition Interlock

Ignition Interlocks

An Ignition Interlock (also called Breath Alcohol Ignition Interlock Device (BAIID) is a device that prevents the functioning of a motor vehicle if the driver’s BAC exceeds a pre-determined level, usually .02 BAC. The technology integrates alcohol breath detection technology to a vehicle’s ignition system. Before the vehicle can be started, the driver must check their BAC by blowing into the ignition interlock. If the driver’s BAC is over the pre-set level the engine will not start. An on-board data recorder logs the event along with other data that is reviewed periodically by court and probation personnel assigned to the case.


How ignition interlock works

The ignition interlock is designed to deter and prevent convicted DUI offenders from operating their vehicles under the influence of alcohol. Depending on the State, judges are empowered to require the installation of the device as a condition of probation for first time or repeat DUI offenders. States are often more likely to require an interlock after multiple DUI convictions, but it can be ordered on first offenses if an offenders BAC was excessively high (at least 0.15 in some states), if injury was caused, or if the subject refused to take a breath alcohol test.

Ignition Interlocks are Costly

DWI probationers using an interlock in their vehicle must pay installation and maintenance fees, must have their interlock serviced every several months, and must provide breath samples every time they drive. In some states offenders are required to obtain a special ignition interlock license that is easily recognizable by Law Enforcement. Costs vary but can easily run a probationer over $1000.00 annually.

Basic Fees Depending on State & Interlock Type
$100 - 200
Monthly Charges
$60 - 100/month
Other Fees Depending on State
Application Fee
First Violation Appointment Fee
Case Management Appointment Fee
Case Management Missed Appointment Fee
Monthly Appointment Fee
Monthly Missed Appointment Fee

Ignition Interlock Companies Shift to Fuel Cell Technology

As with all professionally-used alcohol breath testers, where the results truly do matter and a positive reading can have dire consequences for the subject, the technology used to measure BAC in ignition interlocks has shifted to fuel cells.

Virtually every new ignition interlock being placed into service is now fuel cell based, even though they are much higher in cost than the older SC technology. Although two companies in the interlock business do maintain older, semi-conductor units in service, that is because they are cheap and the companies are allowed to "grandfather" their use. However, some states, such as Texas and Wisconsin, have outright banned the use of semi-conductor interlocks due to their poor and inaccurate performance.

One major flaw of semi-conductor technology is that it characteristically will sometimes signal the presence of alcohol even when none is present; producing what is called a "false positive". Put simply, false positive readings from a testing device can lead to false accusations. In the case of individuals required to use an ignition interlock, the consequence of this instrument error is the false reporting of an attempt to drive while intoxicated, which is serious. This false report automatically enters the individual's record, and can result in extension of their probation period and other very negative legal consequences. Thus, a highly negative report and serious consequence for the individual may result entirely from faulty technology in the ignition interlock.

Once again, where results really matter, the technology that is relied on is always fuel cell.

Who Uses Ignition Interlocks

Most ignition interlocks are primarily intended for DUI offenders but manufactures like Smart Start offer voluntary systems for concerned parents and for businesses that have drivers who have been previously arrested for drunk driving, or for commercial fleet use.

Driver Monitoring

At random times after the engine has been successfully started, the interlock will require additional breath samples from the driver. Running Tests or Rolling Tests as these are called prevent the driver from drinking either inside or outside of the vehicle once it has been started. If the driver fails a running test the ignition will be shut down after the operator is provided sufficient time to safely move the car away from traffic.

Ignition Interlocks also incorporate sophisticated data recorders that monitor and log the actions of the probationer. The devices keep a record of the results of each breath test. This log is printed out or downloaded each time the device's sensors are calibrated, commonly at 30, 60, or 90-day intervals. Case workers and judges conduct periodic reviews of the log. If violations are detected, then additional sanctions can be implemented.

If sentenced offenders are caught driving without an interlock device on their vehicle, punishment can include jail time and/or revocation of their probation. Typically for a first offense an extended 12 months interlock usage may be required. For subsequent offenses, license suspension plus extended interlock usage is common.

Unlike ordinary citizens the ignition interlock user knows with 100% certainty they will be required to have their breath alcohol content measured every time they drive. In a report to Congress by the Department of transportation it was noted that

"Many offenders on interlock programs have a long series of failed attempts to start their vehicle (where the ignition was locked due to the presence of alcohol in the breath sample). Offenders required to use breath alcohol ignition interlocks do not appear to be developing a habit of not driving after drinking; instead they are simply being prevented from doing so by the interlock." - Congress Report.

Know your BAC with LifeGuard Personal Breathalyzer For offenders who persist in drinking the risk is real that sooner or later they will blow over the BAC limit on their interlock and face additional sanctions. A personal breathalyzer check can provide earlier knowledge of dangerous BAC levels to citizens and probationers alike.

Many offenders find their ignition interlock experience expensive, inconvenient, embarrassing and one they are not anxious to repeat. Probationers exiting DUI interlock programs are more likely then those who have never been charged with an alcohol, offense to carry and use a personal breath analyzer to monitor their BAC. Ignition interlocks are not a cure-all to drinking and driving; but together with proper treatment and good BAC knowledge they are making our roads safer.

Additional Information:

Department of Transportation Report Submitted to Congress in December 2007. Download Report

State Ignition Interlock Laws from the National Conference of State Legislatures provides a summary of state by state ignition interlock statutes.