How Ignition Interlocks Work

Interlock DeviceBecause an ignition interlock device must in some form take control over your vehicle, it must be installed by a certified, and in most cases state-approved, provider. In essence, the device has two components. One is a handset, which will be similar in appearance to a phone. The other is a device that links to your vehicle electronically. The two devices communicate with one another through a cord or sometimes wirelessly.

As far as your use of the ignition interlock device, you will find that it is essentially like using a breathalyzer. The device will require you to blow into it, and it will use your breath in order to measure your blood alcohol concentration. When the device is installed, it will be calibrated to contain a threshold level for your blood alcohol concentration. This level will be determined by the state. When the ignition interlock device tests your blood alcohol concentration, it will determine whether or not it is above or below the threshold. If it is above the threshold, then you will be allowed to start your vehicle as normal. If, on the other hand, your blood alcohol concentration is determined to be in excess of the threshold, then you will not be able to start your car.

In many states, the devices are required to administer periodic tests during the vehicle’s operation. When the device attempts to administer one of these periodic tests, the driver will be signaled and required to blow into the device again. As before, if the driver’s blood alcohol concentration is determined to be below the threshold, then the vehicle will continue to function as normal. If the driver’s blood alcohol concentration is determined to be above the threshold, however, then the car will signal for the driver to pull over and turn off the car. It is important to note that the device will not turn off the car while it is being operated.

In general, an ignition interlock device will also be equipped with an electronic log, which will be used by authorities to gauge a user’s compliance. How this electronic log is transmitted to authorities, however, varies by state to state, and can be wireless in some instances.