Question 1

As a general rule, equipment installed in a Class II location must be ________.

Accepted Answer

In Class II locations, which are hazardous due to the presence of combustible dust, equipment must be dust-ignitionproof to prevent ignition of the dust.

Question 2

Describe the mating surfaces of explosionproof equipment.

Accepted Answer

Great care must be exercised when installing or maintaining explosionproof equipment. The improper installation or maintenance of this equipment can completely negate the system's integrity. The mating surfaces of explosionproof boxes are ground flat to provide a very close fit. A screwdriver gouge or deep scratch can provide the exit point for hot gases to escape and ignite the surrounding atmosphere. The ground surfaces of explosionproof enclosures should be cleaned with solvent to remove dirt particles before the parts are bolted together. If it is necessary to remove a substance that cannot be cleaned with solvent, use a fine steel wool; never use sandpaper or a sharp scraping instrument such as a putty knife. All bolts must be in place and tight. If one bolt is missing, the enclosure may not be able to prevent ignition of the surrounding atmosphere in the event of an internal explosion.

Question 3

When horizontal seals are installed,________fiber dams must be used.

Accepted Answer

Two fiber dams are typically used when installing horizontal seals to ensure proper sealing and support.

Question 4

What conditions are required for flexible cords and attachment plugs to be used in hazardous areas?

Accepted Answer

The answer of What conditions are required for flexible cords...

Question 5

In general, the floor area of a garage, up to a level of 18 in. (450 mm) above the floor, is considered to be a________ location.

Accepted Answer

The floor area of a garage up to 18 inches above the floor is considered a Class I, Division 2 location because it is an area where flammable gases or vapors may be present under abnormal conditions.

Question 6

Class III locations are areas that contain combustible________ .

Accepted Answer

The answer of Class III locations are areas that contain...

Question 7

________are used to minimize the passage of gas and to prevent the passage of flame through the conduit.

Accepted Answer

Seals are used in electrical conduits to prevent the passage of gases and flames, ensuring safety in hazardous environments.

Question 8

The________ rating indicates the maximum operating temperature of a luminaire.

Accepted Answer

The T rating indicates the maximum operating temperature of a luminaire.

Question 9

To help prevent condensation, some vertical seals are designed with________ .

Accepted Answer

Drain plugs are used in vertical seals to allow any accumulated moisture to escape, thus preventing condensation.

Question 10

________locations are considered to be the most hazardous.

Accepted Answer

Class I, Division 1 locations are considered the most hazardous because they have ignitable concentrations of flammable gases or vapors present under normal operating conditions.

Question 11

What do Group C and D atmospheres encompass?

Accepted Answer

The answer of What do Group C and D atmospheres...

Question 12

If a stem is longer than________in., lateral braces must be placed within 12 in. (300 mm) of the luminaire, or an explosionproof flexible coupling must be used within 12 in. (300 mm) of the junction box.

Accepted Answer

The answer of If a stem is longer than________in., lateral...

Question 13

When circuit breakers are installed in Class I locations, they must be________ .

Accepted Answer

Circuit breakers in Class I locations, which are areas where flammable gases or vapors may be present, must be explosionproof to prevent ignition of the surrounding atmosphere.

Question 14

A Group A atmosphere contains________ .

Accepted Answer

The answer of A Group A atmosphere contains________ .
...

Question 15

What is the hazard level of an aircraft hangar?

Accepted Answer

The answer of What is the hazard level of an...

Question 16

Some types of explosionproof enclosures are designed to be drilled and tapped in the field. When this is done, at least________ full threads should be engaged between the conduit and the enclosure.

Accepted Answer

The answer of Some types of explosionproof enclosures are designed...

Question 17

Intrinsically safe equipment and circuits operate________ .

Accepted Answer

Intrinsically safe equipment and circuits are designed to operate at low power levels to prevent the possibility of igniting flammable gases or dust in hazardous environments.

Question 18

If it is necessary to remove a substance from the surface of an explosionproof enclosure that cannot be cleaned with solvent, use________ .

Accepted Answer

Fine steel wool is the least abrasive option and will not damage the surface of the enclosure.

Question 19

A Group E atmosphere contains ________.

Accepted Answer

A Group E atmosphere contains combustible metal dusts.

Question 20

What is the difference between Division 1 and Division 2 hazardous locations?

Accepted Answer

The answer of What is the difference between Division 1...

Quiz 20: Hazardous Locations