If your home has carbon monoxide in it you should get out of the house right away but if possible open at least one window and leave your door open when you exit the home to allow the carbon monoxide to escape the house.
You'll need to shut the gas off to your home or have the gas service turn your gas service off to stop your home from producing carbon monoxide.
Carbon Monoxide can result from your gas stove burning or even an oven left on and even from a non vented heater or a furnace that has a blocked exhaust vent or a broken vent allowing the carbon monoxide to escape into your home.
A natural gas water heater can also let off carbon monoxide if the water heater is not vented properly or the vent is obstructed so be sure the vent is in good condition and not blocked.
Once you leave the windows open and doors open and stop the carbon monoxide leak the carbon monoxide should leave the house fully within 24 hours.
You should have a carbon monoxide detector in your home and if it gets too high of a level or you notice headaches then you should leave the house immediately.
Call 911 since a carbon monoxide leak is an emergency that can kill you if you do not get out of the house in time.