UL 913
Intrinsically Safe Apparatus and Associated Apparatus for Use in Class I, II and III, Division 1, Hazardous (Classified) Locations
standard by Underwriters Laboratories, 12/06/2013
UL Subject 1468
Standard for Direct Acting Pressure Reducing and Pressure Restricting Values (Bulletin, 10/9/1998)
standard by Underwriters Laboratories, 10/09/1998