Large congenital nevi form in the womb very early in development, within the first twelve weeks of pregnancy. They are caused by a defect during embryologic development. There is no known method of prevention. They appear in either sex, in all races, and on any areas of the skin.
I recommend that you have a carbon monoxide detector within 15 feet of each bedroom door, 10 feet is even better if you can afford more detectors. If two bedroom doors are 30 feet apart or less, then place one in the middle. If however they are more than 30 feet apart you will need more than one detector.
Therefore, you should install all CO detectors up high, centrally located outside all your sleeping areas, on every floor of your home, in or near any attached garage and any other location per manufacturerâs instruction. You should never install a CO detector near fuel burning appliances and make sure they are replaced every five years. [Editor's note: For more information on carbon monoxide and carbon monoxide detectors, see the following GBA articles:]