Deck 19: Hazardous Locations

Question 1

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.

A) three
B) five
C) seven
D) 11

Answer 1

B

Question 2

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

A) Outlet boxes
B) Seals
C) Fibers
D) Vacuums

Answer 2

B

Question 3

A Group A atmosphere contains ____.

A) hydrogen
B) 2-butanol
C) butadiene
D) acetylene

Answer 3

D

Question 4

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

A) a chisel
B) a putty knife
C) sandpaper
D) a fine steel wool

Question 5

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.

A) 6
B) 10
C) 12
D) 14

Question 6

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

Question 7

What do Group C and D atmospheres encompass?

Question 8

When horizontal seals are installed, ____ fiber dams must be used.

A) two
B) three
C) four
D) five

Question 9

What is the hazard level of an aircraft hangar?

Question 10

Intrinsically safe equipment and circuits operate ____.

A) without electricity
B) at low power levels
C) at high voltage
D) at high current

Question 11

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

A) dustproof
B) dust-ignitionproof
C) explosionproof
D) waterproof

Question 12

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

A) T
B) MOT
C) MT
D) TEMP

Question 13

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.

A) Class I, Division 1
B) Class I, Division 2
C) Class II, Division 1
D) Class II, Division 2

Question 14

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

Question 15

Class III locations are areas that contain combustible ____.

A) dusts
B) gases
C) fibers
D) vapors

Question 16

Describe the mating surfaces of explosionproof equipment.

Question 17

To help prevent condensation, some vertical seals are designed with ____.

A) fiber dams
B) conductors
C) drain plugs
D) horizontal seals

Question 18

A Group E atmosphere contains ____.

A) combustible metal dusts
B) carbonaceous dusts
C) acetaldehyde
D) propylene oxide

Question 19

____ locations are considered to be the most hazardous.

A) Class I, Division 1
B) Class I, Division 2
C) Class II, Division 1
D) Class II, Division 2

Question 20

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

A) dustproof
B) explosionproof
C) waterproof
D) dust-ignitionproof