Chemicals can be both helpful and harmful if not handled properly. There are basic rules of chemical safety that should always be followed which include being aware of the chemicals you are using, being alert, and staying alive by avoiding injury. There are several categories of chemicals that are especially hazardous including acids and bases which can cause chemical burns, flammable materials which can cause heat burns, poisons which can cause injury if ingested, oxidizers which can ignite spontaneously, pyrophoric substances which ignite on contact with air, and carcinogens which can cause long-term health issues like cancer.