Hazardous materials are present in many fixed locations, but it is essential that these hazardous materials be transported to other sites and facilities. This means that materials are present on the highways and railroads of the City of McKinney. Most often, these hazardous substances are released as a result of transportation accidents.
Most hazardous materials are required to be shipped in containers that meet strict specifications established by the Department of Transportation (DOT). DOT labels come in the shape of a 4-inch diamond and are used on individual packages, drums or other small containers. DOT placards are also diamond-shaped (square-on-point), but are larger and found on the outside ends of a transport vehicle.
Placards alert public safety agencies and the general public as to the content of containers and allow visual identification of shipments. They are color-coded and contain symbols and numbers that designate the hazard class or division of the hazardous material that is being shipped. For bulk and certain non-bulk shipments, a four-digit hazardous material identification number may be on the placard, an accompanying orange panel, or a white square-on-point sign.
Hazardous materials are categorized into nine classes:
Flammable and combustible liquids
Flammable solids, spontaneously combustible materials and dangerous when wet materials
Oxidizers and organic peroxides
Toxic (poison or poisonous) material and infectious substances