Nitrapyrin is an organic compound with the formula ClC5H3NCCl3. It is a widely used nitrification inhibitor in agriculture as well as a soil bactericide and has been in use since 1974. Nitrapyrin was put up for review by the EPA and deemed safe for use in 2005. Since nitrapyrin is an effective nitrification inhibitor to the bacteria nitrosomonas it has been shown to drastically the reduce NO2 emissions of soil. Nitrapyrin is a white crystalline solid with a sweet odor and is often mixed with anhydrous ammonia for application.