Dymo Compatible Right to Know Labels with NFPA Diamond communicate the presence of hazardous chemicals to employees or emergency responders. Use these labels to quickly and easily identify and rank the severity of health risks, flammability, instability and special hazards. The National Fire Protection Association (NFPA) diamond is a highly recognizable system used to identify health and physical hazards associated with specific chemicals. Originally developed to aid fire fighters during emergencies in industrial settings, today it is used on Right to Know (RTK) labels and HazCom in order to communicate the presence of hazardous materials.