Any liquid substance that presents a significant riskA measure of loss in terms of both the incident likelihood of occurrence and the magnitude of the consequences. to human health, safety, or the environmentSurroundings or conditions (physical, chemical, mechanical) in which a material exists. The environment plays a significant role in pipeline design, constructio… if it is not properly handled or transported. These liquids may include petroleum products such as crude oil, refined petroleum products, Carbon Dioxide (COA colorless, odorless gas composed of one carbon atom and two oxygen atoms . It is a trace gas in the atmosphere at about 0.04% by volume.2) as a supercritical fluid, or anhydrous ammonia. It may also include hazardous substances such as corrosive chemicals, radioactive materials, and toxic waste.