These devices are sensitive to anything that contains acohol like perfume, hairspray, certain types of food, mouthwash and other products. A person that uses or ingests these products can have a false reading and fail a test which sets off a chain reaction. If they are trying to start the vehicle, the vehicle is locked out for a period of time before they allowed to retest. When the car is in motion and a test is failed the device makes a very loud noise, honks the horn and flashes the lights until the driver pulls over, turns the vehicle off and is able to restart. This goes on their record and is sent to the DMV, often resulting in a longer amount of time they are required to have it on their vehicle or revocation of their license.
Some people that I have talked with recently have said that the device was faulty. Not only did they have false readings, sometimes they couldn't even take the test. Many of these people had to have their vehicles towed to the company that installed the device for maintenance and/or repair. Many of them had bad experiences with the company and were treated poorly as if they had done something wrong.
I am curious if this technology is really ready for prime time. It seems as though they jumped the gun on this, just like they have on so many software programs that required numerous patches to fix all of the problems experienced once it was launched. Maybe these incidents should be reported to the Better Business Bureau (BBB), it's easy to do online at http://www.bbb.org/. At a minimum it will start a record that has to be addressed, other people can use and hold the companies accountable as well as the manufacturers.