My daughters were up over the holiday. My younger one has a 2000 Ford Focus & it needed a few things to get it inspected. I did the work & the last thing was to turn off the "engine light". After it was off I started the engine to make sure. It ran less than 10 seconds. An hour later I happened in the garage & the CO detector was reading 71! No alarm, I guess the alarm goes off at a higher level. I opened the big door & in 30 seconds it went to zero. It just blew me away that such a short run would even register, much less be at a point it might give a human symptoms, headache or whatever. I learned something, any running in a closed space is too much running. In the past I'd think nothing of running a vehicle "a minute" for one reason or another. Never again!