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
Lawn found, in some urban areas, up to 5% of smog was due to small gasoline engines made before 1997, such as are typically used on lawnmowers. Since 1997, the EPA has mandated emissions controls on newer engines in an effort to reduce smog. A 2010 study seemed to show lawn care inputs were balanced by the carbon sequestration benefits of lawns, and they may not be contributors to anthropogenic global warming. However, lawns with high maintenance (mowing, irrigation, and leaf blowing) and high fertilization rates have a net emission of carbon dioxide and nitrous oxide that have large global warming