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
MAPP gas used, supplied in small to medium size containers. Blowtorches are used to brown and sear food cooked by low-temperature sous-vide techniques. Myhrvold recommends in "Modernist cuisine: the art and science of cooking" that MAPP gases should be used in preference to cheaper butane or propane as they produce higher temperatures with less risk of giving the food a gas flavour, as can happen with incompletely combusted gas. MAPP is colorless in both liquid and gas form. The gas has a pronounced acetylene-like or fishy odor at concentrations above 100 ppm, due to the addition of substituted amines as a polymerization