NFPA 505 is a Fire Safety Standard for Powered Industrial Trucks Including Type Designations, Areas of Use, Conversions, Maintenance, and Operation. This standard applies to fork trucks, tractors, platform lift trucks, motorized hand trucks, and other specialized industrial trucks powered by electric motors or internal combustion engines. The table below was taken from section 4.2 of this document.
In laymen's terms, this chart is used to identify what types of trucks (E, ES, EE, EX) may be used in certain hazardous areas. For the purpose of clarity, all the columns except EX have been grayed out.
EX-powered industrial trucks are not permitted to be used in those Locations identified by the letters NA. This includes areas such as Class I, Division 1, Group C. More specifically, you can also refer to the text reference located on the right hand column of the table. Using the same example as above, NFPA 505 paragraph 4.2.1 states;
4.2.1 Class I, Division 1, Groups A,B,C. Powered-operated industrial trucks shall not be permitted to be used in Class I, Division 1, Groups A, B, or C locations.