The Hydrogen Sulfide Gas Breakthrough indicator for Carbon Absorbers and Filters is a colorimetric indicator that indicates the saturation and exhaustion of carbon absorbers and filters. The indicator is reliable and cost effect means for protection from exposure to toxic hydrogen sulfide gas in the work place. The indicator changes color from light blue to black when carbon absorbers and filters are saturated with hydrogen sulfide gas. Hence alerting the user to replace the exhausted carbon absorber or filter. The indicator is easily connected to the ¾ inch female NPT outlet of the carbon absorber or filter using the ¾ inch male NPT threading at the bottom of the indicator. It is highly sensitive to hydrogen sulfide gas with first noticeable color change appears when the indicator is exposed to 1 ppm for 1 hour at air velocity of 30 cm/minute. It operates at temperatures 4oC to 40oC (39oF to 104oF) and humidities 5% RH to 85%RH. The indicator is 3.5 inch tall, 1 inch diameter and you can observe the bright vibrant color change from all directions. The unique design of the indicator prevents any color change from exposure to contaminants in the surrounding environment and changes color only when carbon absorber or filter is saturated. The indicator has extended service life of 14 months.