Explosion Proof Fittings
In locations specified by the NEC© (Articles 510
through 517) as explosion-hazardous, you must install
explosionproof fittings. Locations are classed by
number in descending order of danger: Class 1,
Division 1, highly hazardous; Class 1, Division 2,
slightly less hazardous; and so on.
As an example of explosionproofing, in a gasoline
filling station, the pump island is classed as Class 1,
Division 1. All the conduits in this area must be sealed
with a special sealing fitting. On conduit for lights
above the pumps, the sealing fitting must be located at a
height of not less than 4 feet above the driveway
surface. No junction boxes (explained in the NEC©) or
Condulets may be used in the pump area. Conduits
running from pumps to panels in the building must be
sealed not less than 18 inches above the finished floor of
the building to avoid fumes from the gasoline pumps.
An approved seal must be installed on any conduit
entering or leaving a dispensing pump or the enclosure
on the pump island.
Inside the building of a gasoline station, the Class 1,
Division 1, space extends 18 inches above the floor.
Space above the 18-inch level is classed as Class 1,
Paint spray booths are listed as Class 1, Division 1.
Therefore all fixtures (exhaust fans, air compressors, or
other electrical appliances) located in such booths must
be explosionproof, as well as all switches, convenience
outlets, and motor starters.
Figure 5-58.Explosionproof fluorescent fixture.
Figure 5-59.Explosionproof incandescent fixture.
Figure 5-58 shows an explosionproof fluorescent
lighting fixture for installation in a paint spray room. In
this fixture, the fluorescent tubes are sealed in a larger
glass tube. The four-tube seal ends can be seen in the
figure. The ballast (explained in NEC© Article 410,
Part P) is enclosed in the container above the tube seals.
Figure 5-59 shows an explosionproof incandescent
lighting fixture; figure 5-60 shows an explosionproof
on-and-off switch for lighting.
When the interior wiring system has been
completely installed, make an overall inspection to be
Figure 5-60.Explosionproof ON-and-OFF lighting switch.