2006 Cadillac STS-V Owner's Manual - Page 296

{CAUTION: Snow can trap exhaust gases under your vehicle. This can cause deadly CO (carbon monoxide) gas to get inside. CO could overcome you and kill you. You cannot see it or smell it, so you might not know it is in your vehicle. Clear away snow from around the base of your vehicle, especially any that is blocking your exhaust pipe. And check around again from time to time to be sure snow does not collect there. Open a window just a little on the side of the vehicle that is away from the wind. This will help keep CO out. You can run the engine to keep warm, but be careful. 4-30