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Gaseous & Liquid Nitrogen Hazards and Protection Questions

1. The most critical effect(s) associated with nitrogen exposures is (are)

  1. Tumor induction

  2. Asphyxiation

  3. Cirrhosis of the liver

  4. All of the above

2. O2 deprivation effects resulting from elevated nitrogen levels include which of the following?

  1. Strength impairment

  2. Judgement

  3. Coordination

  4. All of the above

3. Which of the following are correct statements regarding nitrogen-induced asphyxiation?

  1. There is no warning prior to being overcome

  2. Nitrogen rapidly overcomes the victim

  3. O2 deficient atmospheres may exist immediately outside a confined space, especially if the space has nitrogen in it under pressure

  4. All of the above

  5. b and c

4. The most likely physiological effect from exposure to liquid nitrogen is

  1. No effect

  2. Thermal burn

  3. Severe frostbite

  4. None of the above

5. The DOT label code for nitrogen is 2.2. This means that nitrogen is a

  1. Flammable gas

  2. Non-flammable, non-toxic gas

  3. Toxic gas

  4. a or b depending on the state of origin

6. What negative side effects can quickly occur if there is nitrogen exposure in a confined space?

  1. Tingling sensation in the extremities

  2. Asphyxiation

  3. Nausea and vomiting

  4. Rash

7. What are symptoms of exposure to an oxygen-deficient atmosphere?

  1. Dizziness

  2. Salivation

  3. Nausea

  4. Vomiting

  5. Loss of mobility/consciousness

  6. All of the above

8. What rating do the NFPA and HMIS systems assign to the health effects of nitrogen?

  1. 0

  2. 1

  3. 2

  4. 3

  5. 4

9. Is this rating given by NFPA and HMIS systems near the top or bottom of the scale in terms of hazard to human health?



10. An atmosphere of only 4 to 6 percent oxygen causes the victim to fall into a coma in approximately how many seconds?

  1. 20

  2. 40

  3. 60

  4. 90

11. How soon must oxygen be administered to a victim in order to offer a chance of survival?

  1. A few minutes

  2. Half an hour

  3. An hour

Gaseous Nitrogen Properties

12. The molecular weight of nitrogen is 28 g/mol. In the event of a container failure and the release of liquid nitrogen 100% concentration, it would be reasonable to expect the nitrogen gas to:

  1. Seek out the lowest points in the facility

  2. Rise to the highest points

  3. Be dispersed throughout the area

13. Which of the following are characteristics of nitrogen?

  1. Colorless

  2. Odorless

  3. Chemically unreactive/inert

  4. All of the above

  5. a and b

14. Combination of nitrogen with halogens and sulfur gives rise to very explosive compounds including

  1. Halogen azides

  2. Sulfur nitride

  3. Both of the above

15. Nitrogen is the main constituent of air, comprising of ____%

  1. 62

  2. 93

  3. 78

16. Nitrogen changes from a gas to a liquid at ______ ℉

  1. 32

  2. 100

  3. -320

  4. -460

17. At a constant temperature, the volume of a given quantity of any gas varies inversely as the pressure to which it is subjected is a statement of:

  1. Avagadro’s Law

  2. Boyle’s Law

  3. Charles’ Law

  4. Graham’s Law

18. Which of these statements are true?

  1. A gas is a substance that boils between absolute zero and ambient temperature

  2. A vapor is formed from evaporating liquids

  3. A fume is formed from molten metal or welding

  4. All of the above

19. What is the composite molecular weight of air?

  1. 8

  2. 18

  3. 25

  4. 29

20. A _____ is usually shipped at higher pressure at 70℉ in heavy steel cylinders.

  1. Gas

  2. Fume

  3. Vapor

  4. Non-liquified gas

21. The scientific definition of a gas is a material that boils between _____ and _____ ℉.

  1. Absolute zero, 0

  2. Absolute zero, 80

  3. 0, 32

  4. 32, 100

22. Nitrogen is a(n) _____ gas

  1. Toxic

  2. Inert

  3. Flammable

23. Gaseous nitrogen is typically stored in

  1. High-pressure tube trailers

  2. Plastic cylinders

  3. Plexiglass tube trailers

24. What happens to nitrogen when it's exposed to high temperatures?

  1. It shrinks

  2. It expands

  3. Nothing happens

25. What QVL (grade) in nitrogen is specified for general industrial usage, inerting, and heat treatment applications?

  1. R

  2. B

  3. M

  4. L

26. What is the min. nitrogen % for QVL grade B?

  1. 98.3%

  2. 27.5%

  3. 99.0%

  4. 99.998%

27. True or False: nitrogen has an odor

  1. True

  2. False

28. What is the odor threshold for nitrogen?


29. If a nitrogen leak were to occur, it would most probably be found:

  1. At the ceiling

  2. At the floor

  3. Dispersed throughout the room

30. At what temperature does nitrogen auto ignite?


31. True or False: nitrogen is likely to cause ground pollution.

  1. True

  2. False

32. Which of the following can be contacted to determine proper methods of disposal for nitrogen gas?

  1. Local environmental agency

  2. State environmental agency

  3. Provincial environmental agency

  4. Federal environmental agency

  5. All of the above

Liquid Nitrogen Properties

33. Satisfactory materials for use with liquid nitrogen include

  1. 18-8 stainless steel

  2. Copper

  3. Monel

  4. Brass

  5. Aluminum

  6. Carbon steel

  7. a-e

34. Appropriate clothing for use with liquid nitrogen includes which of the following?

  1. Non-absorbent loose-fitting leather gloves that can be easily removed if liquid should splash onto, or into them.

  2. Non-woven materials to minimize becoming saturated with cold liquid.

  3. Goggles and face shields to protect the eyes and face where spraying or splashing of liquid may occur.

  4. Overalls, or similar clothing made without open pockets or turn-ups where liquid could collect and worn outside boots.

  5. All of the above

35. True or False: OSHA standard 29 CFR 1910.151(c) requires that an eyewash and safety shower be in close proximity to storage and handling locations for injurious corrosive chemicals. This standard then requires that an eyewash and safety shower be located in close proximity to the storage and handling areas for liquid nitrogen.

  1. True

  2. False

36. True or False: if liquid nitrogen enters an enclosed flask that is then warmed to room temperature, it could vaporize and in doing so would expand 696:1, possibly resulting in an over-pressurization of the flask and a subsequent explosion.

  1. True

  2. False

37. True or False: the cold boil-off vapor of cryogenic liquids rapidly freezes human tissue. Most metals become stronger upon exposure to cold temperatures, but materials such as carbon steel, plastics and rubber become brittle or even fracture under stress at these temperatures.

  1. True

  2. False

38. Atmospheric air that comes into contact with the outside of a pipe or metal surface that is at or below liquid nitrogen’s boiling point (-320F) may condense into a liquid. Since O2 has a higher boiling point (-297F) than the N2 in the air, the condensed air may be

  1. O2 enriched

  2. O2 deficient

  3. In a vacuum

  4. Pressurized

39. If you chewed frozen graham crackers and then emitted “smoke” from your mouth and nostrils it would be the result of

  1. Cigarette smoke the instructor had previously inhaled being crystallized and expunged by the LN2

  2. Exponential warming of the carbohydrates in the crackers

  3. Frozen water vapor emitted from the instructor’s mouth and nostrils

  4. Nitrogen gas becoming visible after contacting saliva in the instructor’s mouth and being released as a vapor

40. Immersing a rose into a dewar of LN2 and then crushing it by hand is indicative of the risks of LN2 to

  1. Quickly freeze human tissue

  2. Allow frozen human tissue to be shattered

  3. Both of the above

41. If a frozen tennis ball shattered and emitted a loud bang when thrown against the floor, it was the result of the

  1. Impact of the frozen ball striking the floor

  2. Expansion of the air inside the ball when it struck the floor

  3. Both of the above

42. If LN2 were tossed across the floor then gathered the dust from the floor and deposited it at the wall it would be an indication of

  1. The new FDA and JHAC standards for cleanliness measurements

  2. The ability of LN2 to solidify dust and move it in the direction that it was flowing

  3. Neither of the above

  4. ________ (fill in the blank)

43. Cooking an egg to a hard-boiled state in LN2 then shattering it and watching it return to a liquid state demonstrates that LN2

  1. Can freeze and then allow the frozen materials to be shattered

  2. Eggs are one class of material not susceptible to being permanently altered by LN2 exposure

  3. Both the above

  4. Neither the above

44. A match re-ignited into a flame from an ember when exposed to the condensation on the outside of the metal cup containing LN2 is the result of

  1. LN2 being ignitable under specific conditions

  2. O2 in the air being frozen and since it has a boiling point less than of N2, sliding down the cup and contacting the ember of the match

  3. Neither of the above

45. Placing the LN2 into a metal tube, inserting a rubber stopper, then activating the spark plug before the rubber stopper was ejected, is possible due to

  1. Ignition of the N2 by the spark plug

  2. Rapid expansion of the N2 in the tube and an increased pressure above atmospheric in the tube

  3. Both the above

  4. Neither of the above

46. Freezing an orange and banana and then using them to drive a 16d nail into a 2 x 4 is an example of LN2’s ability to make solid and liquid objects rigid.

  1. True

  2. False

47. Cryogenic liquids have a boiling point below ___ ℉.

  1. 212

  2. 32

  3. 0

  4. -150

48. A _____ will not recondense into a liquid except at very low temperatures


49. When liquified gases under pressure are released they can

  1. Vaporize rapidly and cool to temperatures that can cause frostbite

  2. Cause an explosion

  3. Vaporize slowly and will take time before affecting employees

  4. Vaporize slowly and then explode

50. Recommended materials for transporting liquid nitrogen are

  1. 18-8 stainless steel

  2. Nickel-chromium alloys

  3. Copper

  4. All of the above

Respirator Use

51. True or False: a self contained breathing apparatus (SCBA) should be used in instances where exposure levels are not known.

  1. True

  2. False


52. True or False: air-purifying respirators will provide protection in an oxygen deficient environment.

  1. True

  2. False

53. Are persons who use breathing apparatus required to be trained by the OSHA standards?

  1. Yes

  2. No

54. What does a comprehensive management system for supplied air include?

  1. Continuous monitoring of air supply

  2. Routine inspection and replacement of supplied-air hoses

  3. Restriction of vehicular traffic in the area of supply hoses

  4. All of the above

55. When using supplied air, a worker should carry a small backup cylinder/escape pack attached to a different supplied-air system with enough breathing air to last how many minutes?

  1. 1 to 2 minutes

  2. 5 to 10 minutes

  3. 20 to 30 minutes


Nitrogen Workplace Incidents

56. True or False: according to CSB data, over 60% of workplace fatalities and injuries from breathing nitrogen-enriched air involved victims who were working in or next to a confined space.

  1. True

  2. False

57. What percent of fatalities from Chemical Safety Board data were due to attempts to rescue injured persons in confined spaces?

  1. 2

  2. 5

  3. 10

  4. 20

58. True or False: data shows that employees and contractors are often both victims of nitrogen asphyxiation in the workplace

  1. True

  2. False

59. True or False: 13 percent of nitrogen asphyxiation incidents involved maintenance activities

  1. True

  2. False

60. True or False: 14 percent of nitrogen asphyxiation incidents involved trenches and manholes.

  1. True

  2. False

61. True or False: there were 85 nitrogen-related accidents in the U.S. from 1992—2002 documented by the U.S. Chemical Safety Board that resulted in the deaths of 80 persons.

  1. True

  2. False

Nitrogen Cylinders

62. What is a requirement for nitrogen gas cylinders?


63. Nitrogen cylinders should be stored in a

  1. Cool, dry place

  2. Warm, dry place

  3. Cool, damp place

  4. Warm, damp place

64. What is the maximum amount of time a nitrogen cylinder should be stored for?

  1. 2 weeks

  2. 1 month

  3. 6 months

  4. 1 year

  5. 3 years

65. How large of a container can nitrogen be shipped in?

  1. 100 mL

  2. 125 mL

  3. 550 mL

  4. 1 L

  5. 1350 mL

66. What is the maximum gross mass vessel in which nitrogen can be shipped?

  1. 30 kg

  2. 100 kg

  3. 5 kg

  4. 20 kg

67. True or False: cylinders for nitrogen, industrial grade air, and breathing-quality air should have distinct and incompatible fittings that cannot be cross connected.

  1. True

  2. False

68. Liquified gases in cylinders are kept liquid by

  1. High pressure

  2. Low temperature

  3. Vapor pressure

  4. Adiabatic pressure



Workplace Air Quality Standards

69. Ventilation systems should be equipped with

  1. Emergency shutoff valves

  2. Sprinklers

  3. Malfunction alarms

  4. “On” Button

70. What is a warning sign that there is too much nitrogen in the atmosphere?

  1. Burning eye sensation

  2. There are no warning signs

  3. Rotten egg smell

  4. Sweet smell

71. Oxygen concentrations must be kept at _____ or above in buildings where nitrogen is stored/used.

  1. 19.5%

  2. 21.5%

  3. 67.8%

  4. 32.9%

72. What is required if a worker is in an area with less than 19.5% oxygen concentration?

  1. They are only allowed to be in the area for 30 minutes before they must take a break

  2. They must be wearing special breathing equipment

  3. They must be with a partner in case something goes wrong

  4. None of the above

73. Which one(s) of the following actions(s) should be undertaken if a nitrogen leak is discovered or if an alarm sounds?

  1. Evacuate personnel to safe areas

  2. If possible to do so safely, shut off the source of the leak

  3. Monitor oxygen levels and provide maximum ventilation

  4. Initiate the emergency plan and make the required emergency contacts

  5. All of the above

74. In testing for atmospheric hazards, what is the order in which the tests would be performed?

  1. Combustible gases and vapors, oxygen, toxic gases and vapors

  2. Oxygen, combustible gases and vapors, toxic gases and vapors

  3. Oxygen, toxic gases and vapors, combustible gases and vapors

  4. Toxic gases and vapors, oxygen, combustible gases and vapors

75. Is the order in which the tests are performed regulated by the OSHA Standards?


76. If so, which standards are applicable?


77. True or False: ventilation is not required in rooms or chambers into which nitrogen may leak or vent.

  1. True

  2. False

78.How should a nitrogen leak be cleaned up?

  1. Wait 1 hour for it to dissipate

  2. Ventilate the area

  3. Nothing needs to be done

79. When should a valve be closed?

  1. After each use

  2. When piping is empty

  3. Valves should never be closed

  4. b and c


Nitrogen Blanketing

80. What is nitrogen blanketing?


81. Nitrogen gas is most commonly used for blanketing because it is

  1. Inert

  2. Widely available

  3. Relatively inexpensive

  4. All of the above

82. What are the benefits of nitrogen blanketing?

  1. Protect plant personnel, products, and plant assets by reducing the oxygen content in the vapor space of a storage tank/process vessel

  2. Eliminate possibility of fire or explosion

  3. Decreases evaporation

  4. Protects tank from structural corrosion damage caused by air and moisture

  5. Prevents air, moisture, and other contaminants from entering the vapor space and causing product degradation

  6. All of the above

83. How does blanketing prevent air and other contaminants from infiltrating and causing oxygen degradation and spoilage of sensitive materials?

  1. By increasing carbon dioxide levels inside storage containers

  2. By increasing oxygen levels inside storage containers

  3. By creating a slight positive pressure inside storage containers

  4. By creating a slight negative pressure inside storage containers

84. Which is not an element needed to create a fire?

  1. Oxygen

  2. Fuel

  3. Carbon dioxide

  4. Ignition source

85. What are some ways that a storage tank can be made inert?

  1. Reducing the oxygen content of a vapor space to a value that is less than the concentration that will support combustion

  2. Reducing the fuel concentration in the vapor space to a value less than the minimum concentration that can support combustion

  3. Increasing the fuel concentration in the vapor space to a value greater than the maximum concentration that can support combustion

  4. All of the above

86. True or False: fixed roof tanks must be blanketed with nitrogen.

  1. True

  2. False

87. True or false: nitrogen blanketing systems are essential in spaces that are not sealed tight enough to hold a slight positive pressure.

  1. True

  2. False

88. Which is not a method commonly used for nitrogen control for use as an inert gas?

  1. Continuous purge

  2. Pressure control

  3. Density control

  4. Concentration control

89. What are some disadvantages of continuous purge systems?


90. True or False: pressure-control systems can be employed for tanks that are not sealed.

  1. True

  2. False

91. The amount of nitrogen required to blanket a tank under pressure control is the sum of which two values?

  1. Nitrogen required based on the tanks’ working throughput

  2. Nitrogen required by thermal breathing

  3. Nitrogen required by atmospheric levels

  4. a and b

  5. a and c

  6. b and c

92. True or false: concentration control is suitable for unsealed tanks.

  1. True

  2. False

93. True or False: nitrogen usage is optimized when utilizing concentration control methods.

  1. True

  2. False

94. What is a confined space in the workplace?


95. True or False: a worker should check air quality before entering a confined space.

  1. True

  2. False

96. True or False: if one were serving as the attendant as a member of a confined space entry team and was maintaining all parts of one’s body outside the plane of the opening to the confined space which contained nitrogen, then this would eliminate any exposure to the nitrogen.

  1. True

  2. False

97. If you were entering an area with a confined space, what components of the atmosphere would you want to test?


98. What are some warning and protection systems for confined spaces and their entry portals?

  1. Flashing lights

  2. Audible alarms

  3. Auto-locking entryways to prevent access

  4. All of the above

99. Which is not a reliable method of immediately retrieving immobilized workers in the event of continuous monitoring, ventilation failure, or another emergency condition?

  1. Attaching a body harness and lifeline to personnel entering confined areas

  2. Wristlets or anklets attached to a lifeline, along with a retrieval mechanism

  3. Allowing personnel to enter the confined area with proper training, rescue equipment, and dependable breathing air

  4. Allowing personnel to quickly enter the confined area without breathing in air


For discussion or answers to any of the questions, please contact us.

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