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.
Installation and maintenance costs can range from a few hundred dollars for low-cost systems to thousands. The standard stand-alone units retail for roughly $15-$60, depending on the type. Stand-alone units can be installed by anyone, very similar to a smoke detector, but of course you can also hire a handyman to do it.They will charge a minimal fee, usually under $100 including the cost of the detector.Carbon monoxide gas has roughly the same density as air, and so unlike smoke, it does not tend to rise. This means that you can install your carbon monoxide detector near the floor or near the ceiling, or anywhere in between.tand-alone units can be installed by anyone, very similar to a smoke detector, but of course you can also hire a handyman to do it. They will charge a minimal fee, usually under $100 including the cost of the detector.