Do not use cooking stoves to try to provide heat. Do not use outdoor propane or charcoal grills indoors. Follow manufacturers' guidelines when using wood stoves or kerosene heaters. Install a carbon monoxide detector. Early symptoms of carbon monoxide poisoning include headache, nausea, dizziness, unclear thinking, shortness of breath, and weakness.
Severe symptoms can include unconsciousness and convulsions.
If you suspect carbon monoxide poisoning, don't wait to see what happens.