Gastec Hydrogen Fluoride Gas Detector Tube features 7 pump strokes and 1/2 correction factor for 0.25 - 0.5 ppm measuring range, 4 pump strokes and 1 correction factor for 0.5 - 20 ppm measuring range and 1 pump strokes and 5 correction factor for 20 - 100 ppm measuring range. Detector tube with sampling time of 45 sec per pump stroke is ideal to detect hydrogen fluoride in air or the industrial areas and environmental atmospheric condition. Detector with 0.1 ppm detecting limit, changes color from yellow to brown.