Hydrogen sulfide occurs naturally in sulfur springs, swamps and salt marshes, and is often associated with the decomposition of organic material. H2S has a characteristic rotten egg smell which can be detected at very low levels before it cause health effects. Our AE452 – H2S TEST KIT (Hydrogen Sulphide) is a cost effective and convinent method for periodic monitoring H2S in water.. The end point is very sharp and easily discernable by the user.