How Do Ignition Interlock Devices Work? An ignition interlock device is a small handheld breathalyzer device used in vehicles to measure the amount of alcohol present in an individual’s breath. These types of devices are commonly installed as requirements following offenses involving drunk driving, such as:

  • DWI
  • DWI 2nd
  • Felony DWI (3rd or more)
  • Intoxication Assault
  • Intoxication Manslaughter

There are many courts who require people accused of these offenses to install the machine in any vehicle they own or possess as a condition of bond. The judges justify the requirement as a means to protect the safety of the community. Additionally, those who are convicted of offenses such as DWI could have their license suspended, and the only way to obtain an occupational license to drive legally in Texas with a conviction suspension on their record is to install one of these devices.

An ignition interlock device prevents an individual from starting a vehicle until they have taken a breath alcohol test first. In the event that the device registers the blood alcohol content of an individual as being over a pre-programmed limit, then the vehicle will not start. Many manufacturers and interlock service providers set the limit between 0.02 – 0.04 blood alcohol concentration (BAC).  If the sample provided by the driver does not exceed the BAC limit, then the vehicle will start.  The machine will also prompt the driver to provide follow-up or “rolling” samples while driving to continue traveling. 

These devices typically must be serviced and calibrated at authorized service centers on a regular basis. While the actual length between these appointments vary from court to court, they generally take place every 30 to 60 days.

The length of time an individual convicted of a drunk driving offense must have an ignition interlock device installed in their vehicle depends not only the circumstances of their case, but also the defendant’s prior history of DWI offenses and the judge deciding the term. For instance, if someone has been convicted of a DWI for the first time, they could find themselves having to have an ignition interlock device installed for a period of 90 days or up to one (1) year. However, someone convicted of a DWI for the second time, or more, may have to deal with having one of these types of devices for up to two years.

The defendant is the one responsible for paying the fees associated with an ignition interlock device. There are several different companies and auto-repair shops in our area that have been approved as ignition interlock service providers by Harris, Fort Bend, Galveston, and Montgomery County courts and probation/supervision departments.

The costs can be broken down into four different categories:

*Installation fee: varies from approximately $75 to $150, depending on where the device is installed.

*Monthly fees: approximately $75 to $100, which includes monthly monitoring, maintenance, calibration and lease fees.

*Reset fee: required when locked out of the vehicle because of violations on the device, which ranges from $25 to $50

*Removal fee: approximately $45 to $75.

How Do Ignition Interlock Devices Work? Thank you for visiting Collin Evans Law’s blog, a Houston criminal defense law firm. For more information about ignition interlock devices, you may call our office for a free consultation. Get the information and legal advice you are seeking at (713) 225-0650.