Carbon monoxide, is a highly poisonous, colorless and odorless gas that easily spreads through the air. It is produced as a result of incomplete combustion of fuels such as: wood, oil, gas, gasoline, kerosene, propane, coal, oil. Since this gas is colorless and odorless, it is so important to detect the dangerous concentration of carbon monoxide early in the rooms we stay in because it poses a serious threat to human health and life. Protect yourself and your family from the silent killer !! The CTW-04 sensor is used to constantly monitor the dangerous concentration of carbon monoxide in the air. When a dangerous concentration is detected, the device activates sound and visual alarm. It is equipped with a built-in non-replaceable battery sufficient for the entire life of the sensor (10 years!) Eliminating the need for periodic battery replacement. The sensor has an auto-diagnostic system that signals sensor damage. Its next advantage is the very small compact dimensions (the smallest carbon monoxide sensor with a built-in battery in the world).