Posted By Jane Blunt There isn't enough information to say. First, is this ammonia gas, or ammonia in solution? RIDDOR states 'accidental release or escape of any substance in a quantity sufficient to cause the death, major injury or other damage to the health of any person'. So whether or not you report depends on a) the chemical form the ammonia was in, and b) whether the circumstances of release constituted a risk of death or major injury. Jane