Learning
Fires or explosions may only occur when ? basic condition(s) exist(s).
3
Which of the following materials would be found in one of the three location classes of the class/division system?
I. Combustible dust
II. Combustible fibers/flyings
III. Combustible liquid-produced vapors
IV. Flammable gases
V. Flammable liquid-produced vapors
VI. Ignitible fibers/flyings
All of the above
The possibility that a gas mixture may be above the upper flammable limit does not ensure that the gas is safe. The gas must first pass through the flammable range as its ? increases from being below the lower flammable limit to a concentration above the upper flammable limit.
Concentration
A source of ignition is all that is needed to create a fire or an explosion when an ignitible or explosible mixture of a flammable gas or a combustible dust is mixed with air or oxygen in proportions that create an ignitible or explosible mixture.
true
Materials in Class I, Division 1 and Division 2 hazardous (classification) locations are assigned to one of ? groups.
4
A Class I, Division 2 location is one in which flammable gases, flammable liquid-produced vapors, or combustible liquid-produced vapors ? .
I. are handled, processed, or used but normally confined within closed containers or systems
II. are in an area adjacent to a Class I, Division I location where positive-pressure ventilation prevents communication of the materials into the adjacent area
III. are normally prevented from becoming ignitible concentrations by using positive mechanical ventilation
IV. are not present
1,2,3
An alternate “zone classification” system found in Article ? was added to the NEC in 1996.
505
Metal combustible fibers/flyings are classified as ? .
Metal combustible fibers/flyings are classified as ? .
An area where nonmetal combustible fibers/flyings are in the air under normal operating conditions in quantities sufficient to produce explosible mixtures would be classified as Class III, Division 1.
true
Explosionproof equipment is defined as equipment enclosed in a case that is capable of withstanding an explosion of a ? gas or vapor that may occur within it and of preventing the ignition of a specified gas or vapor surrounding the enclosure by sparks, flashes, or explosion of the gas or vapor within, and that operates at such an external temperature that a surrounding flammable atmosphere will not be ignited.
specified
Protection technique concepts include ? .
I. Isolation of Electric Parts from Hazardous Materials
II. Prevention of External Ignition and Explosion
III. Prevention of Internal Ignition and Explosion
IV. Separation of Hazardous and Non-Hazardous Equipment
1, 2, 3
A Class II liquid has a flash point at or above ? but below 140°F.
100 degrees F
Article 505 of the NEC has ? revisions in the 2023 edition.
135
The flash point of a liquid is the minimum temperature at which it gives off vapor in ? concentration to form an ignitible mixture with the air near the surface of the liquid, as specified by test.
sufficient
The purged and pressurized protection technique is permitted in any hazardous (classified) location for which it is ? .
Identified
Portable utilization equipment that is or may be used within a hangar shall be of a type ? for use in Class I, Division 2 or Zone 2 locations.
Suitable
The area classification is Class I, Division 2, for indoor non-overhead type dispensing devices with gravity ventilation up to 18 in. above floor level, extending ? horizontally in all directions from dispenser.
25'
Emergency shutoff devices or disconnects shall be installed in approved locations but not less than ? or more than 100 ft from the fuel dispensing devices that they serve.
20'
Electrical wiring and utilization equipment used within the classified areas inside and outside of membrane enclosures during spray painting shall be ? for the location.
Suitable
A Class I, Division 1 location is a location in which ignitible concentrations of such flammable gases, flammable liquid–produced vapors, or combustible liquids above their flash points ? exist frequently because of repair or maintenance operations or because of leakage.
Might
Associated apparatus not suitable for installation in a hazardous (classified) location shall be required to be marked only with 506.9(C)(2)(2) and (C)(2)(3), and where applicable (C)(2)(4), but BOTH the symbol ? in 506.9(C)(2)(2) and the symbol for the type of protection in 506.9(C)(2)(3) shall be enclosed within the same square brackets.
AEx
If flexible connections in Zone 20 locations are subject to oil or other corrosive conditions, the insulation of the conductors shall be of a type ? for the condition or be protected by means of a suitable sheath.
Listed
Electrical equipment installed in Zone 20, 21, and 22 hazardous (classified) locations shall have the temperature markings specified for ignitible fibers/flyings, less than 165°C (329°F) for equipment that is not subject to overloading, or ? for equipment (such as motors or power transformers) that may be overloaded.
I. 120°C
II. 120°F
III. 248°C
IV. 248°F
1 & 4
Type ITC cable or Type ITC-ER cable as permitted in ? and terminated with listed fittings is permitted in Zone 22. Type ITC-ER cable shall include an equipment grounding conductor in addition to a drain wire.
335.4
Lamps and lampholders for fixed lighting that is located over lanes in commercial garage Class I locations through which vehicles are commonly driven or that might otherwise be exposed to physical damage shall be located not less than ? above floor level, unless of the totally enclosed type or constructed so as to prevent escape of sparks or hot metal particles.
12'