Also, what if I'm the designated driver and I'm taking 3 of my drunk friends home. How likely would this system be to give a false positive and now the respons

Also, what if I'm the designated driver and I'm taking 3 of my drunk friends home. How likely would this system be to give a false positive and now the responsible person's car won't start until you get a bunch of drunks out of the car and air it out.