An ignition interlock device works in a manner that is very similar to a breathalyzer. It is installed in your vehicle in such a way that requires you to use it before operating the vehicle. You will blow into the ignition interlock device, which is calibrated to measure your blood alcohol concentration. If the ignition interlock device measures your blood alcohol concentration at a level that is below the threshold that has been established by the state and assigned to your device, then you will be allowed to start your car. If, however, your blood alcohol concentration is determined to be above that threshold, then you will not be permitted to start and operate your vehicle.
In addition to performing such a test before starting the car, many states require that the device test you at random intervals while you are operating the vehicle. The device will signal to you that it is time to test your blood alcohol concentration, and you will be required to blow into the device as before. Provided that you continue to register a blood alcohol concentration that is below the device’s threshold, you will be allowed to continue operating the vehicle. If, however, you register a blood alcohol concentration that is above the threshold, your vehicle will then signal that you must pull over. It is important to note that the device will not stop your car from functioning will you are operating it. However, the signal will be such that you will have no other choice but to pull the car over and turn it off.
An ignition interlock device is also typically connected to an electronic log. Many states will require you to come in to have this log examined on a periodic basis. The frequency of these tests varies from state to state. You may also find that some states require that the information from the ignition interlock device be transmitted to authorities wirelessly. Finally, due to the sensitivity of ignition interlock devices, they will also periodically need to be calibrated by providers that your state approves.