Gastec Hydrogen Sulfide Gas Detector Tube features 2 - 10 pump strokes and 1/2 - 1/10 correction factor for 10 - 100 ppm measuring range, 1 pump strokes and 1 correction factor for 100 - 2000 ppm measuring range and 1/2 pump strokes and 2 correction factor for 2000 - 4000 ppm measuring range. Detector tube with sampling time of 45 sec per pump stroke is ideal to detect hydrogen sulfide in air or the industrial areas and environmental atmospheric condition. Detector with 2 ppm detecting limit, changes color from white to brown.