Electrochemical amperometric sensors are widely used in environmental monitoring and in biomedical applications. These sensors have selectivity, fast response time, are small in size, use very low power, are easy to use and are potentially low cost. However, the conventional aqueous electrolyte based amperometric sensors have many drawbacks: they have limited operating life because of the high vapor pressure of aqueous based electrolytes, have poor baseline stability due to the build up of reaction products, and are expensive.To overcome these limitations, Honeywell has developed a new class of electrochemical gas and vapor sensors based on nonaqueous electrolytes. These sensors have a wide operating voltage, a wide operating temperature and have the potential for a long operating life. These sensors also have multigas sensing capability. Sensor prototypes have been built and have been used to monitor the partial pressures of carbon dioxide and oxygen, as well as low levels of gases, such as carbon monoxide, nitrogen dioxide and ammonia.This paper describes the theoretical considerations and presents experimental results. The advantages and disadvantages of electrochemical sensors vis-a-vis semiconductor based sensors are also discussed.