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
Small engine dimensions and power output, relative to larger automobile engines. Power output ranges from less than 1 to about 15 horsepower. The smallest of all are used in handheld garden machinery, such as string trimmers and chainsaws, which may be as small as piston displacement. The most common are four-stroke air-cooled single-cylinder engines running on either petrol or diesel. Engines for small machinery that must be hand-carried, such as string trimmers and chainsaws, are usually a two-stroke design, which is lighter for any given power output. However, two-stroke engines create a relatively large amount of air pollution and noise pollution, and