How Do Car Breathalyzers Work

Car Breathalyzer Devices, also called Ignition Interlock Devices (IID), are a small device that is about the size of a cell phone. The device is connected to your vehicle’s ignition system.

Prior to starting the vehicle, you are required to blow into the device to submit a breath sample. The device measures your breath alcohol level and compares it to a pre-set limit. If your breath alcohol level is below the pre-set limit, the vehicle will start. If your breath alcohol level is at or above the pre-set level, the IID will prevent the vehicle from starting.

While you are operating the vehicle, the IID will alert you to submit a breath sample. This breath samples are random and are typically required several times while you are operating the vehicle. If the device detects that you have a breath alcohol level above the pre-set limit while you are driving, depending on your jurisdiction, the device will sound an alarm and may also trigger the vehicle’s horn and/or flash the lights until you turn off the vehicle. For safety reasons, the IID will not turn off the vehicle if your breath alcohol level is above the pre-set limit while you are operating the vehicle. Some devices also notify law enforcement if your breath alcohol level is above the pre-set limit while you are operating the vehicle.

Some circumstances result in the device going into a permanent lockout mode. This may include a specific number of failed attempts to start the vehicle, attempts to circumvent or disable the device or missed service appointments. If the vehicle is placed in a permanent lockout mode by the IID, contact your service provider to have the device reset.

The pre-set level varies from state-to-state and is based on the state’s DUI laws. The limit depends on the state in which you were convicted for driving under the influence and the nature of your conviction. Some states have zero tolerance laws that set the allowable breath alcohol level well below the state definition for DUI. Other states use the same breath alcohol level that is used to determine if someone is driving under the influence.

The state and the court system determine which device you are required to have as part of your agreement to drive. The service provider will review the device’s features and operating instructions with you when the Car Breathalyzer Device is installed.