Gas detector in industrial refrigeration processes and biological degradation processes, including exhaled breath. Depending on the required sensitivity, different types of sensors are used (e.g., flame ionization detector, semiconductor, electrochemical, photonic membranes). Detectors usually operate near the lower exposure limit of 25ppm; however, ammonia detection for industrial safety requires continuous monitoring above the fatal exposure limit of 0.1%. There are several different sensors that can be installed to detect hazardous gases in a residence. Carbon monoxide is a very dangerous, but odorless, colorless gas, making it difficult for humans to detect. Carbon monoxide detectors can be purchased for around US$20–60. Many local
Gas engine 1-hour rating, 12-hour rating and continuous rating) where as the gas engine will generally only have a Continuous rating, which will be less than the Diesel Continuous rating. Various ignition systems have been used, including hot-tube ignitors and spark ignition. Most modern gas engines are essentially dual-fuel engines. The main source of energy is the gas-air mixture but it is ignited by the injection of a small volume of diesel fuel. Gas engines that run on natural gas typically have a thermal efficiency between 35-45% (LCV basis)., The best engines can achieve a thermal efficiency of slightly more than 48%