NFPA (Fire) 497

Classification of Flammable Liquids, Gases or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas, 2012 Edition
standard by National Fire Protection Association, 01/02/2012

NFPA (Fire) 472

Standard for Competence of Responders to Hazardous Materials/Weapons of Mass Destruction Incidents, 2018 Edition
standard by National Fire Protection Association, 08/21/2017