TERMINAL ENCLOSURE DESCRIPTIONS
M1- GENERAL PURPOSE (NEMA I)
Nonventilated enclosure to prevent accidental contact with enclosed apparatus, suitable for use indoors where not subjected to any unusual opperating conditions, to provide protection against dirt, light and indirect splashing, but not dust tight.
M5- MOISTURE RESISTANT
M6- EXPLOSION RESISTANT
M7- COMBINATION MOISTURE TIGHT, EXPLOSION RESISTANT
M6 and M7 ENCLOSURES FOR USE IN HAZARDOUS LOCATIONS
M6 and M7 explosion resistant enclosures involve the use of a wiring enclosure for use in hazardous location conditions:
    Class I Groups C and D, Division 1 and 2
    Class II Groups E, F anf G, Division 1 and 2
    Class III Division 1 and 2
Contact CEMELECTRIC for item suitable for Class I, Group B hazardous locations

M6 and M7 TERMINAL ENCLOSURES

    CSA LR55274-24
    NRTL/C Certified to U.S. Standards
    Class I, Div. 1, Groups B, C and D
    Class II, Groups E,F and G
    Class III
Specifying an Explosion Resistant Electrical Enclosure
CLASSIFICATION OF HAZARDOUS ATMOSPHERES†  (Based on Electrical Code and UL)
Class Division Group  Typical atmosphere/ignition temps Devices Covered Temperature Measured Limiting Value
1
Gases
Vapors		 1
Normally
hazardous
  A  acetylene (305C, 581F)
 All electrical devices and wiring Maximum external temperature in 40C ambient See Sect. 500-2 of NEC
  B   butadiene1 (420C, 788F)
ethylene oxide2 (429C, 804F)
hydrogen (400C, 752F)
manufactured gasses containing more than
   30% hydrogen by volume
propylene oxide2 (449C, 840F)
  C   acetaldehyde (175C, 847F)
cyclopropane (500C, 932F)
diethyl ether (160C, 320F)
ethylene (490C, 914F)
unsymmetrical diamethyl hydrazine (UDMH 1.1-dimethyl hydrazine) (249C, 480F)
  D   acetone (465C, 869F)
acrylonitrile (483C, 898F)
ammonia3 (651C, 1204F)
benzene(560C, 1014F)
butane (405C, 761 F)
1-butanol (butyl alcohol) (365C, 689F)
2-butanol {secondary butyl alcohol) (405C, 761F)
n-butyl acetate (425C, 797F)
isobutyl acetate (421G, 790F)
ethane (515G, 959F)
ethanol (ethyl alcohol) (356C, 689F)
ethyl acetate 472C, 800F)
ethylene dichioride (413C, 775F)
gasoline (56—60 octa?le: 280G, 53SF)(100 octane 456G, 853F)
heptanes (280C, 536F)
hexanes (225C, 437F)
isoprene (220C, 428F)
methane (natural gas) 482 to 632C, 900 to 1170F)
methanol (methyl alcohol) (385C, 725F)
3,methyl-1-butanol (isoamyl alcohol)(350C, 662F)
methyl ethyl ketone (516C, 960F)
methyl isobutyl ketone (460C, 860F)
2-methyl-1-propanol (isobutyl alcohol) (427C, 800F)
2-methyl-2-propanol (tertiary butyl alcohol)(480C, 896F)
petroleum naphtha4 (288C, 550F)
octanes (220C, 428F)
pentanes (260C, 500F)
1-pentanol (amyl alcohol) (300C, 572F)
propane (450C, 842F)
1-propanol (propyl alcohol) (440C, 824F)
2-propanol (isopropyl alcohol) (399C, 75OF)
propylene (460C, 860F)
styrene (490C, 914F)
Toluene (480C, 896F)
vinyl acetate (427C, 800F)
vinyl chloride (472C, 882F)
xylenes (530C, 986F)
  1. Group D equipment shall be permitted for this atmosphere if such equipment is isolated in accordance with Section 501-5(a) by sealing all conduit 1/2-inch size or larger.
  2. Group C equipment shall be permitted for this atmosphere if such equipment is isolated in accordance with Section 501-5(a) by sealing all conduit 1/2-inch size or larger.
  3. For Classification of areas involving ammonia atmosphere, see Safety Code for Mechanical Refrigeration (ANSI B9.1-1971) and Safety Requirements for the Storage and Handling of Anhydrous Ammonia (ANSI K61.1-1972).
  4. A saturated hydrocarbon mixture boiling in the range 20—135°C (68—275°F. Also known by the synonyms benzene, ligroin, petroleum ether or naphtha.

†For a complete list noting properties of flammable liquids, gases and solids refer to the latest edition of NFPA No. 325M.