The ignition interlock system can be set anywhere from .00% BAC to slightly higher levels, but typically not above .04% BAC.
An ignition interlock system works by measuring the BAC or blood alcohol concentration also referred to as BAL or blood alcohol level of the vehicle's driver before and during the operation of said vehicle.
If the blood alcohol concentration registered by the ignition interlock system is higher than the preprogrammed level that was set by the company that installed the ignition interlock system, the vehicle will not start. The courts in each state determine the programmed level that will be set by the company performing the installation. Typically this level will be between .02% and .04% depending on the state law.
How Does An Ignition Interlock System Work
Also at random intervals while the vehicle is in operation, the ignition interlock system will require breath samples from the vehicle operator in order for the vehicle to continue operating. If a breath sample is not provided, or the sample that is registered by the ignition interlock system exceeds the limit that has been preset by the ignition interlock provider, the unit will record the occurrence, warn the driver and then start its alarm, which will consist of the lights flashing, horn honking, etc.
When it is time for a breath sample, the ignition interlock system will let the driver know that a sample is required. The ignition interlock system will allow enough time for the driver to safely pull to the side of the road before the sample must be given.