A simple, reusable, credit card size device that indicates the ultraviolet light intensity. Excessive levels of UV light can cause sunburn, premature aging of the skin, and skin cancer. Carbon monoxide, or CO, is a colorless, odorless, toxic gas. It is produced by the incomplete combustion of solid, liquid, and gaseous fuels. Appliances fueled with gas, oil, kerosene, or wood may produce CO. Use a Carbon Monoxide detector to detect if such appliances are not installed, maintained, and used properly, CO may accumulate to dangerous and even deadly levels in cars, homes, or poorly ventilated areas. Common sources of CO include the following wood or gas fueled appliances: