A CHE can be an efficient and safe source of heat for your iguana, but only if you use them properly. Be sure to read all of the directions and cautionary statements supplied by the manufacturer. Be safe, use your common sense, and above all, be careful - not only with CHEs, but with other heating and lighting devices as well. In addition to CHEs, there are other methods of providing nighttime heat, such as letting your iguana sleep on a human heating pad wrapped in a soft towel. It can be dangerous to use heating pads for long time periods unsupervised, so CHEs are probably the better way to go.
Some people use nighttime blue or red light bulbs to provide warmth at night.
Some iguanas do not mind this at all, while others are bothered by the light and have trouble sleeping. You may want to watch your iguana carefully for signs of stress if you decide to try these nighttime bulbs. There are other methods of providing heat in addition to the methods discussed above. Remember - the absolute best source of UV light is the sun. The use of artificial UV bulbs in your iguana's basking area is strongly recommended, however.