Understand that carbon monoxide is a colorless, odorless gas, so even if you have carbon monoxide in your home, you can't detect it by smell or sight.
Know the symptoms of carbon monoxide poisoning: headaches, feeling weak, nausea and perhaps vomiting or loss of muscle control. Unfortunately, the symptoms are very similar to flu symptoms.
Remember, carbon monoxide is a byproduct of combustion and can come from a multitude of sources including furnaces, fireplaces, gas- or diesel-burning generators, charcoal grills and kerosene or propane space heaters.
Purchase a carbon monoxide detector and install it, preferably in the hallway outside of the sleeping areas in your home. Similar to smoke detectors, carbon monoxide detectors continuously monitor the air and sound an alarm if carbon monoxide levels rise. Carbon monoxide detectors are available as plug-ins or powered by batteries, but remember, if you choose a battery-powered model, be sure to change the batteries every 6 months.
Preferably before the heating season starts, have your heating system inspected by a qualified technician to ensure no cracks have developed in your burners or furnace vents.
Be sure your fireplace is installed according to the fire code and have your chimney and flues checked to be sure they are sound.
Never use a charcoal grill indoors to cook or provide heat and be sure to use any propane or gas heaters according to the manufacturer's instructions and ensure adequate ventilation.
Only buy heating appliances (space heaters) that have been approved by an independent testing laboratory such as Underwriters Laboratory (UL).