Nothing bad happened. Yesterday it was about 45 degrees outside. I decided to ride my bike to the gym. I opened the garage door and started the bike to let it warm up. It ran about 5 minutes, with the garage door open while I got ready. Anyway, I took off, and must of left the door between the garage and and the kitchen open.
Even with the main garage door open there was enough Carbon Monoxide in the garage to set off my detector. When I got home the detector was warning me to get out of the home. I opened the windows and aired out the house,and put new batteries in all my detectors.
Just a good reminder that even with the garage door open, it is still a bad idea to warm the bike inside the garage.

 

That's good to know...

 

One thing that was making things worse could have been Ur furnace running...
That draw will make a negative pressure and actually pull the air from the garage into house

 

Yeah, carbon monoxide can be sneaky stuff. Forget the exact temp, but lets say 68 degrees it is lighter than air, below that temp heavier and can travel thru forced air furnace ducts or remain in the lower regions of the house dependant on thge temperature.

 

CO monitors with a digital readout are my favorites. I always caution people to get good ones with the digital readouts. They don't have to buy the best but I would not risk my life and family to the cheapest made. JMO. A digital readout can show a trend before it becomes a problem.

 

Next door neighbor always warms up his old pickup about 20 minutes before he takes off. A couple of days ago there were 2 fire engines and an ambulance in front of his house. Went to see whats up. His two kids were standing outside in there pajamas and it was only about 20 degrees. The truck having been running allowed carbon monoxide to be sucked into the front door. The kids stayed with me until they blew all of the gas out of the house. I told him he should run is truck out closer to the street from now on. The dumb *** had it running in the same spot the next day!

 

Here in CA all houses are supposed to have a spring closer on the door between the garage & house for just such an occasion. Glad you caught it.