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
Southern California Gas Company the Los Angeles Gas Company in 1890. These companies ultimately became Southern California Gas Company. By the early 20th century, natural gas—a colorless, odorless gas found in association with oil underground—was starting to gain attention. The breakthrough came with the discovery of the Buena Vista Oil Field near Taft, California in 1909, which included a huge reservoir of natural gas. Since natural gas had twice the heating value of manufactured gas, the company took the bold step to convert its system to natural gas and build pipelines throughout the state. Natural gas was soon found throughout the country, and demand