You've probably heard of carbon monoxide poisoning, and if you're like most people, you know it can occur if your heating system malfunctions or is not vented properly. But this is not the only possible cause of carbon monoxide poisoning. This poisonous gas is produced whenever any fuel -- be it wood, propane, oil, or natural gas, is burned. In that light, here's a look at four silly mistakes that may lead to carbon monoxide (CO) poisoning.

Lighting a fire before checking the chimney.

If your chimney is plugged or if there is a lot of creosote buildup within it, then when you light a fire in your fireplace, the smoke -- and the CO it contains -- will billow into your home. Even after the smoke seems to dissipate, the CO may linger. Since it is lighter than air, it may slowly travel to the upper floors of your home, causing CO poisoning later on as you sleep. The moral of the story here is to never start a fire before checking to ensure the chimney is clear. And have your chimney inspected once a year to check for venting issues, too.

Putting the generator too close to your home.

Right next to your home is a convenient place for your gas or oil-burning generator, right? While it might be convenient, it is not safe. CO produced by the generator can enter the home through open windows, gaps between windows and their frames, and vent systems. In the 2004-2005 hurricane season, about half of all fatal CO poisoning incidents were attributed to generators that were placed within 7 feet of the home. Be on the safe side, and place your generator at least 25 feet from your home.

Heating your home with a gas range.

When it's a little chilly and you don't want to turn the heat on, resist the urge to heat up your home with the gas range. While it may save you a few cents on the energy bill, it will put you at risk of carbon monoxide poisoning as the open flame will generate CO that accumulates in your home.

Using a portable gas heater indoors.

Portable gas heaters made for camping use should only be used outdoors -- not inside the home. They release CO as they burn gas. If you want a portable heater for indoor use, purchase an electric one, as these don't burn any fuel and therefore won't release any CO.

As an extra precaution, always make sure your carbon monoxide detectors are working.