Types of Gas Detectors: (5) Ultrasonic Detectors: Ultrasonic gas detectors use acoustic sensors to detect changes in the background noise of its environment. Since most gas leaks occur in the ultrasonic range of 25 kHz to 10 MHz, the sensors are able to easily distinguish these frequencies from background noise which occurs in the audible range of 20 Hz to 20 kHz. The ultrasonic gas leak detector then produces an alarm when there is an ultrasonic deviation from the normal condition of background noise. Despite the fact that Ultrasonic gas leak detectors don't measure gas concentration, the device is still able to determine the leak rate of an escaping gas. By measuring its ultrasonic sound level, the detector is able to determine the leak rate, which depends on the gas pressure and size of the leak. The bigger the leak, the larger its ultrasonic sound level will be. Ultrasonic gas detectors are mainly used for outdoor environments where weather conditions can easily dissipate escaping gas before allowing it to reach gas leak detectors that require contact with the gas in order to detect it and sound an alarm. These detectors are commonly found on offshore and onshore oil/gas platforms, gas compressor and metering stations, gas turbine power plants, and other facilities that house a lot of outdoor pipeline