Winter, CO and you!
 

It is winter and in the winter we tend to fly with the heating system on. This is exactly what I have done today while taking off with my wife.
10 min. into the flight I have checked the newly fitted ‘spot’, i.e. the CO Detector,
it was black!
I opened the storm window and the cabin vents and shut off the heating. Upon a second check I have noticed that I actually opened the defrost and the cabin heat to Max. while leaving the fresh air vents shut. I will not tell you about the headache that I have suffered later (the mrs. was fine). I have fitted the CO Detector today for the first time! Make sure that you fit yours!! IT MIGHT SAVE YOUR LIFE!!!

Couldn't agree more. An old friend of mine was lost due to being overcome by CO escaping from his exhaust system.

This always freaks me out.

I fly in Canada, and tend to use the "long johns, jacket and thick socks" heating system instead! (I may change my tune in the next few months, however!)