TopTes PT520B+ Gas Detector could quickly and accurately detect gas leaks from hard-to-reach areas for methane, propane, natural gas, LPG, etc. PT520B+ could recharge more than 3000 times. *Note: Please allow 30 seconds of warm-up time before the operation. TopTes PT520B+ could respond to gas leaks in 0.5s. The current gas concentration will be displayed in PPM or %LEL in four-digit reading. Besides, 11 colored bars and 75dB alarm will warn you out of danger and lead to gas leakage. Visual and audible alarm will react seriously as the gas concentration increase. *Detection Range: 50-10000ppm. TopTes PT520B+ could detect any hard-to-reach area with a 17-inch gooseneck like gas stoves, natural gas lines, and basements. High and Low sensitivity could promote more accurate detection. Once gas leaks detected, you could turn it zero by ZERO button.