Explosion Protection Guide
Classifications Inside North America
Classes |
Class I |
Flammable gases or vapors are present in the air in quantities sufficient to produce explosive or ignitable mixtures. |
Class II |
Combustible or conductive dusts are present. |
Class III |
Ignitable fibers or flyings are present, but not likely to be in suspension in sufficient quantities to produce ignitable mixtures. (Group classifications are not applied to this class.) |
Divisions |
Division 1 |
The substance referred to by class is present during normal conditions. |
Division 2 |
The substance referred to by class is present only in abnormal conditions, such as a container failure or system breakdown. |
Groups |
Group A |
Acetylene |
Group B |
Hydrogen (or gases of equivalent hazard) |
Group C |
Ethylene (or gases of equivalent hazard) |
Group D |
Gasoline (or gases of equivalent hazard) |
Group E |
Metal Dust |
Group F |
Coal Dust |
Group G |
Grain Dust |
Classification Outside North America
Zones |
Zone 0 |
Area in which an explosive gas-air mixture is continuously present or present for long periods. |
Zone 1 |
Combustible or conductive dusts are present.Area in which an explosive gas-air mixture is likely to occur in normal operation. |
Zone 2 |
Area in which an explosive gas-air mixture is not likely to occur, and if it occurs it will only exist for a short time. |
Protection Types |
|
|
Zone |
d |
Flameproof (Explosion proof) Enclosure |
1,2 |
e |
Increased Safety |
1,2 |
ia |
Intrinsic Safety |
0,1,2 |
ib |
Intrinsic Safety |
1,2 |
o |
Oil Immersion |
2 |
p |
Pressurized Apparatus (Purged Apparatus) |
1,2 |
q |
Powder Filling (Sand Filling) |
2 |
m |
Encapsulation |
1,2 |
n |
Normally Nonsparking and/or Nonincendive Circuits) |
2 |
Temperature Codes |
|
°F |
°C |
T1 |
842 |
450 |
T2 |
572 |
300 |
T3 |
392 |
200 |
T4 |
275 |
135 |
T5 |
212 |
100 |
T6 |
185 |
85 |
Groups |
Group I |
For application in below ground installations (mines) where methane (firedamp) and coal dust may be present. |
Group IIA |
For application in above ground installation where hazards due to propane may exist. This group most closely matches the North American Group D. |
Group IIB |
For application in above ground installations where hazards due to ethylene may exist. This group most closely matches the North American Group C. |
Group IIC |
For application in above ground installations where hazards due to hydrogen or acetylene may exist. This group most closely matches the North American Groups A and B. |