UL has released a new edition of UL 844, the standard for Luminaires for Use in Hazardous (Classified) Locations. This revision to ANSI/UL 844 is being issued to add a new paragraph, 37.5. On the UL website, you can either purchase the entire 13th edition or just the revised pages.
1.1 These requirements cover fixed and portable luminaires for installation and use in hazardous (classified) locations, Class I, Divisions 1 and 2, Groups A, B, C, and D; Class II, Division 1, Groups E, F, and G; Class II, Division 2, Groups F and G; and Class III, Divisions 1 and 2, in accordance with the National Electrical Code, NFPA 70.
1.2 These requirements also cover luminaires for installation and use in Class I, Zones 1 and 2, Groups IIA, IIB, IIB plus Hydrogen, and IIC, and Zone 20, 21 and 22 hazardous (classified) locations in accordance with the National Electrical Code, NFPA 70.
1.3 These requirements cover luminaires for use only under the following atmospheric conditions:
a) A minimum ambient temperature of minus 25°C (minus 13°F);
b) An oxygen concentration not greater than 21 percent by volume; and
c) A nominal barometric pressure of one atmosphere.
*Description from the UL standards sales site.