If your family has started exhibiting unusual respiratory symptoms that do not seem to have any obvious cause, you may start to suspect that your home's furnace is emitting carbon monoxide. If you believe this may be the case, and you do not yet have a carbon monoxide detector, check your furnace for the following signs.

1.  Excessive Black Spots Above The Pilot And Burner

When trying to determine whether your furnace may be producing carbon monoxide gas, one of the first places you should look is on the metal plate above the burner, as well as the one housing the pilot light, if they are in different compartments. Normally, you may find small spots of black soot directly above the flames.

However, if the plates are covered with soot or you notice black streaks along the side walls, this is a sign that the flames are burning off too much natural gas. The excessive black coatings are carbon, which is a byproduct of burning too much gas at one time.

If you do find excessive black spots or streaks, there may be an issue with the air and gas exchange or the thermocouple feeding the pilot light. If you do not have a professional inspect the issue, the carbon will continue to build and the flames will continue to release carbon monoxide into your home's air. 

2.  Pilot Light Changes Color

While you are checking the metal plates surrounding the pilot light, also take note of the flame's color. When the ratio of air and gas are in balance, the pilot light should burn a cool blue color.

However, when not enough air is mixing with the gas that feeds the pilot light, it will start to glow a yellowish to orange color. However, this issue could have another cause, such as a blockage in the line or rust covering the pilot flame's hole. When you notice changes in the pilot color, have it checked immediately to make sure it is not producing carbon monoxide.

If you find that your furnace is exhibiting any of the above signs, and you do not already have one, purchase a carbon monoxide detector to see if you have unusually high levels in your house. If so, contact a heating repair professional who offers heating repair services to have them inspect the unit as soon as possible and take the necessary action to fix any issues that are causing carbon monoxide production in your home.