saw a news story about the danger of keyless ignitions, seems a small
subset of the drivers often forget to actually hit the start/stop button
to actually turn the car off. One woman said that this happened to her
and she woke up to her kids screaming headache, deciding to take the kid
to the ER she opened the garage door and was overwhelmed by the fumes
after having left the car run for 5 hours.

Aside from the fact that this indicates a pretty bad problem with
isolating the garage from the house properly or that in five hours she
never heard the car running, the real question is: could a car run for 5
hours in a "sealed" garage?

I would expect the car might overheat or run out of oxygen. So, how long
could you expect a car to run in a "sealed" garage?