Final answer:
The oxidizer class of chemical hazards is represented by the white (bottom) diamond in the NFPA 704 Hazard Identification System. It warns about the fire hazard posed by substances with oxidizing properties.
Step-by-step explanation:
The oxidizer class of chemical hazards is represented by the white (bottom) diamond in the National Fire Protection Agency (NFPA) 704 Hazard Identification System. This white diamond indicates special hazards, such as the presence of oxidizers, which allow a substance to burn in the absence of air or oxygen.
An example of an oxidizer is potassium dichromate, which contains oxygen that can cause other materials to combust.
The oxidizer pictogram warns users about the fire hazard posed by substances with oxidizing properties.