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
Pullstring changes the doll's eye color. Other non-doll toys like See 'n Say (1965). The earliest patent with a pullstring included in it is an 1886 "Toy Bowling-Alley". Many motorized lawn mowers, chainsaws, portable generators, and portable outboard motors use a pullstring or pullcord attached to a handle as a manual ignition device. Some vehicle engines are also started with pullchains, such as the early-1900s Puckridge, or pullcords, like the pre-release version of the Citroën 2CV car, and the DKW RT 125 scooter. Some grenades such as the German Models 24, 39, and 43 have pullcords. Some machine guns such as