Isocyanic acid is a chemical compound with the formula HNCO. It is a colorless liquid that has a pungent odor and is known for its reactivity. Isocyanic acid can be produced through various chemical processes, including the thermal decomposition of urea or the reaction of phosgene with ammonia. This compound is significant in organic chemistry and is used in the synthesis of various isocyanates, which are important in the production of polymers and foams. Isocyanic acid is also studied for its potential effects on human health and the environment, as it can be toxic in certain concentrations.