Graphology - the study of handwritings; autograph - written with one's own hand; seismograph - a machine noting strength and duration of earthquakes. marina - a harbor for pleasure boats; maritime - relating to the sea; submarine - an undersea boat; aquamarine - color of sea water.
Chemicals are classified into various hazard classifications in accordance with their physiochemical properties and health hazards. Each class of chemical has a pictorial symbol called a danger symbol.
Groups further define the hazard in Class I and Class II areas. In Class I, there are Group A (Acetylene and similar gases), Group B (Hydrogen and similar gases), Group C (Ethylene and similar gases) and Group D (Propane and similar gases). Hazardous dusts and fibers (Class II & III respectively) are not treated in Article 505.