Fire-Inspector-II 67 - Fire Inspector II Exam Questions and Answers

Paint Spray Booth Clearance Requirements

According to the International Fire Code (IFC) 2021, Section 2404.3.2, paint spray booths must have a minimum clearance of 18 inches from unprotected combustible materials.

This clearance requirement helps prevent heat transfer, fire spread, and ignition of nearby combustible materials due to the operation of the spray booth.

2. Why 18 Inches is the Correct Answer

Spray booths generate overspray, vapors, and heat, making clearance essential for fire prevention.

The requirement applies to combustible walls, ceilings, and storage materials surrounding the spray booth.

If combustibles are within 18 inches, additional fire protection such as fire-rated barriers or sprinkler protection may be required.

3. Verification of Other Options

Option A (12 inches) – Incorrect, as the IFC mandates a minimum 18-inch clearance.

Option C (24 inches) – Exceeds the standard clearance requirement but is not the official minimum. Incorrect.

Option D (36 inches) – Some jurisdictions may require larger clearances, but IFC mandates 18 inches as the minimum. Incorrect.

Reference Sources:

International Fire Code (IFC) 2021 – Section 2404.3.2 (Paint Spray Booth Clearance Requirements)

NFPA 33: Standard for Spray Application Using Flammable or Combustible Materials (Clearance Guidelines)

ICC Fire Inspector II Study Guide (2021)

Thus, the correct and verified answer is: B. 18 inche

Definition of a Control Area

According to the International Fire Code (IFC) 2021, Section 202 (Definitions) and Section 5003.8.2 (Control Areas), a control area is a building or portion of a building where specific amounts of hazardous materials can be stored, dispensed, used, or handled without requiring additional fire protection features.

The purpose of a control area is to limit the risk associated with hazardous materials while still allowing their use in limited quantities.

2. Why Hazardous Materials is the Correct Answer

Control areas apply to a wide range of hazardous materials, including flammable, combustible, corrosive, toxic, and oxidizing substances.

The amount of each hazardous material that can be stored in a control area is regulated by IFC Table 5003.1.1(1).

3. Verification of Other Options

Option B (flammable liquids only) – Incorrect, because control areas allow multiple types of hazardous materials, not just flammable liquids.

Option C (combustible liquids only) – Incorrect, as combustible liquids are just one category of hazardous materials.

Option D (corrosive materials only) – Incorrect, since control areas are not limited to corrosive materials but include all types of hazardous materials.

Reference Sources:

International Fire Code (IFC) 2021 – Section 202 (Definitions of Control Area)

IFC 2021 – Section 5003.8.2 (Control Areas and Hazardous Material Limits)

NFPA 1: Fire Code (Hazardous Materials Storage Regulations)

According to the International Fire Code (IFC) 2021, when specific fire safety requirements are not explicitly provided for in the code, the responsibility to determine the applicable requirements falls upon the Fire Code Official.

Reference from the IFC (2021):

IFC Section 104.1 – General Authority and Responsibilities:

This section explicitly grants the Fire Code Official the authority to interpret the code and determine the necessary safety measures in cases where the code does not provide specific guidance.

It states: "The fire code official is hereby authorized to enforce the provisions of this code and shall have the authority to render interpretations of the code and to adopt policies and procedures in order to clarify the application of its provisions."

IFC Section 104.9 – Alternative Materials and Methods:

This section further supports the authority of the Fire Code Official by allowing them to approve alternative fire safety measures when strict compliance with the code is not feasible.

Why Other Options Are Incorrect?

A. City Manager:

The city manager is responsible for administrative and operational management but does not have the authority to interpret or enforce fire code requirements.

B. Legal Counsel:

Legal counsel provides legal advice but does not have jurisdiction over fire safety code enforcement.

C. Board of Appeals:

The board of appeals reviews disputes and interpretations made by the Fire Code Official, but they do not have primary responsibility for determining applicable fire safety requirements.

Final Conclusion:

The Fire Code Official is the designated authority responsible for interpreting and applying fire safety requirements in situations where the International Fire Code (IFC) does not explicitly provide specific provisions.

The storage of liquefied petroleum gas (LP-gas) in containers by dealers awaiting resale is regulated by the 2021 International Fire Code (IFC), Section 6109 – Storage of Portable LP-Gas Containers.

IFC 6109.11 – Storage Within Buildings Not Accessible to the Public:

"Storage of LP-gas containers in buildings that are not accessible to the public shall be limited to a maximum aggregate quantity of 2,000 pounds water capacity at one location."

Why Other Options Are Incorrect?

A. 735 lb. – Too low; the maximum allowed is 2,000 lb.

B. 1,000 lb. – Incorrect; IFC allows up to 2,000 lb.

D. 2,500 lb. – Exceeds the 2,000 lb. maximum permitted storage quantity.

✅ Correct Answer: C. 2,000 lb.

Fire flow for residential buildings is determined based on IFC Appendix B, Table B105.1(1) – Required Fire Flow for One- and Two-Family Dwellings, Group R-3, and R-4 Buildings.

For a 3,700 sq. ft. two-family dwelling of Type VB construction:

Per Table B105.1(1), the baseline fire flow is 1,750 gpm.

If an NFPA 13D-compliant automatic sprinkler system is installed, the fire flow is reduced by 50%.

1,750 gpm × 0.50 = 875 gpm, but the minimum allowed for a sprinklered dwelling is 1,000 gpm.

✅ Correct Answer: B. 1,000 gpm

IFC Section 901.5 (Acceptance Tests) requires fire protection systems, including fire alarms, to be tested upon completion to ensure compliance with NFPA 72 (National Fire Alarm and Signaling Code) and the IFC. The contractor’s verification of full compliance (B) signals readiness for the official acceptance test by the fire code official, ensuring all components are installed and functional. Option A (zone-by-zone testing) is impractical for final acceptance. Option C ties the test to water supply, irrelevant to alarms. Option D (one year) is excessive and not required by IFC or NFPA 72 for initial acceptance. Thus, B is correct.

Understanding Type III Construction

According to the International Building Code (IBC) 2021, Section 602.3, Type III construction is a mix of noncombustible and combustible materials.

Exterior walls must be noncombustible or fire-retardant-treated wood, while interior structural elements (such as floors, roofs, and partitions) can be wood.

2. Common Uses of Type III Construction

Churches, schools, apartment buildings, and mercantile (retail) structures are often built using Type III construction because it balances fire resistance with cost-effectiveness.

Many low-rise residential and commercial buildings use this type due to its ability to support multiple stories while maintaining some fire protection.

3. Verification of Other Options

Option A (Type I) – Incorrect, as Type I construction is entirely noncombustible (steel/concrete) and used for high-rises, not typical for churches, schools, or apartments.

Option B (Type II) – Incorrect, as Type II construction is fully noncombustible but has lower fire resistance than Type I, mainly used for commercial buildings, warehouses, and low-rise offices.

Option D (Type IV) – Incorrect, as Type IV (heavy timber) is rarely used for schools and apartments, though some older churches may use it.

Reference Sources:

International Building Code (IBC) 2021 – Section 602.3 (Type III Construction Definition)

NFPA 220: Standard on Types of Building Construction

ICC Fire Inspector II Study Guide (2021)

Thus, the correct and verified answer is: C. Type III. ✅

Storage of fine magnesium scrap is regulated under 2021 IFC Chapter 59 – Magnesium and specifically IFC Section 5904.3.2.5 – Separation Distances for Magnesium Scrap Storage.

IFC 5904.3.2.5 – Minimum Separation Distances:

Fine magnesium scrap in quantities greater than 1,000 cubic feet must be separated from all buildings (except those used for magnesium scrap recovery) by at least 250 feet.

Why Other Options Are Incorrect?

A. 30 feet – Too close; insufficient for high-risk metal fires.

B. 50 feet – Does not meet the minimum required separation for magnesium scrap.

C. 100 feet – While larger, it still does not meet the 250-ft. requirement

Battery-charging areas for industrial trucks (such as forklifts) present a fire hazard due to the potential for flammable hydrogen gas buildup and electrical malfunctions. To mitigate this risk, portable fire extinguishers with a minimum rating of 40-B:C are required.

Reference to Fire Inspector Documentation:

1. 2021 International Fire Code (IFC) – Section 309.5 (Fire Extinguishers for Battery-Charging Areas)

IFC 309.5 states that battery-charging areas must have a portable fire extinguisher with a minimum rating of 40-B:C to handle potential electrical and flammable liquid fires.

The B rating covers flammable liquid fires (such as battery electrolyte leaks), while the C rating ensures it is safe for electrical fires.

2. NFPA 10 – Standard for Portable Fire Extinguishers (2022 Edition)

NFPA 10, Table 6.3.1.1 outlines that industrial battery-charging areas must have at least one extinguisher rated 40-B:C.

This ensures adequate fire suppression capability for both electrical and flammable liquid hazards.

Detailed Explanation of Answer Choices:

Option A (Incorrect): 4-A:20-B:C includes a higher A-rating (for ordinary combustibles), but 20-B:C is below the required 40-B:C.

Option B (Incorrect): 3-A:40-B:C exceeds the B:C requirements but adds an unnecessary A-rating, which is not specified in the code.

Option C (Incorrect): 2-A:10-B:C is insufficient, as it does not meet the 40-B:C minimum requirement.

Option D (Correct): 40-B:C is the correct and minimum required rating per IFC 309.5 and NFPA 10.

Thus, the correct and verified answer is: D. 40-B:C.

1.

Exit Sign Letter Height Requirement

According to the International Fire Code (IFC) 2021, Section 1013.5, and the International Building Code (IBC) 2021, Section 1013.5, exit sign letters must be at least 6 inches in height. However, the minimum height requirement for the wording within the sign (e.g., "EXIT") is specifically 4 inches.

The stroke width of these letters must be at least 0.5 inches to ensure visibility.

2. Verification of Other Options

Option A (three inches) – Below the minimum height requirement. Incorrect.

Option C (five inches) – Exceeds the minimum standard but is not the correct minimum required size. Incorrect.

Option D (six inches) – This applies to the total EXIT sign height, but the actual letter requirement is 4 inches. Incorrect.

Reference Sources:

International Fire Code (IFC) 2021 – Section 1013.5

International Building Code (IBC) 2021 – Section 1013.5

NFPA 101: Life Safety Code (Exit Sign Requirements)

IFC Section 3804.1 classifies aerosol storage as Group H (high-hazard) if flammable, fitting option A. Options B and C are subgroups (H-2, H-3), while D (Group S-1) is for moderate-hazard storage, not applicable. This is consistent with the study guide's occupancy classifications.

References: Fire Inspector II Study Guide, IFC Section 3804.1.

In nonsprinklered occupancies, newly upholstered furniture in common areas must resist ignition by cigarettes primarily in Group I-2 occupancies (such as hospitals, nursing homes, and care facilities). This requirement reduces the risk of fire ignition in environments where occupants may have limited mobility and are unable to evacuate quickly.

Reference to Fire Inspector Documentation:

1. 2021 International Fire Code (IFC) – Section 805.2 (Ignition Resistance of Upholstered Furniture and Mattresses)

IFC 805.2 specifies that nonsprinklered Group I-2 occupancies must have upholstered furniture that resists ignition by cigarettes because these settings involve vulnerable populations who may need assistance in an emergency.

2. NFPA 101 – Life Safety Code (2021 Edition) – Section 10.3.2 (Fire-Retardant Upholstered Furniture)

NFPA 101, Section 10.3.2 aligns with the IFC in requiring that furniture in health care facilities (Group I-2) must meet fire resistance standards to prevent ignition from cigarettes and other sources.

Detailed Explanation of Answer Choices:

Option A (Correct): Group I-2 (hospitals, nursing homes, and assisted living facilities) is required to have cigarette-ignition-resistant upholstered furniture in nonsprinklered common areas.

Option B (Incorrect): Group A-1 (theaters and performing arts venues) does not have this requirement, as seating arrangements are different and typically involve fire-resistant materials.

Option C (Incorrect): Office spaces (Business Occupancies, Group B) do not require ignition-resistant furniture under fire code regulations.

Option D (Incorrect): Libraries in Group E (Educational Occupancies) are not required to have this furniture unless otherwise specified by local codes.

Thus, the correct and verified answer is: A. Group I-2

 Reference to Fire Code Requirements for Clearance Between Combustible Fibers and Sprinklers:

The International Fire Code (IFC 2021), Section 3206.6, states that the minimum clearance between the tops of piles of combustible fibers and sprinkler deflectors shall be no less than 3 feet.

This requirement ensures that the sprinkler system operates efficiently and that water distribution is not obstructed in case of a fire.

 Fire Safety Concerns:

Combustible fibers pose a high fire risk due to their flammability and tendency to generate large amounts of heat and smoke.

Adequate clearance prevents heat accumulation near the sprinkler heads, ensuring they activate at the correct temperature.

 Clarification of Incorrect Answer Choices:

A. 2 ft. → Incorrect

Too low and could obstruct sprinkler operation, reducing water distribution effectiveness.

C. 4 ft. → Incorrect

Exceeds the required minimum per the IFC 3206.6 standard, though more clearance is beneficial.

D. 5 ft. → Incorrect

More than the code requirement, but the mandatory clearance is 3 feet.

 Conclusion:

The correct and verified answer is B (3 feet) based on IFC 3206.6, ensuring proper sprinkler performance and fire safety for combustible fiber storage.

Foamed plastics or materials containing foamed plastics used for stage scenery must meet strict fire performance requirements to prevent rapid flame spread and fire hazards in assembly occupancies.

The correct fire test standard for these materials is UL 1975 – Standard for Fire Tests for Foamed Plastics Used for Decorative Purposes.

Reference to Fire Inspector Documentation:

1. 2021 International Fire Code (IFC) – Section 807.4.2 (Foamed Plastics for Stage Scenery)

IFC 807.4.2 states that foamed plastics used in scenery must be tested and approved per UL 1975 to ensure fire safety.

2. UL 1975 – Standard for Fire Tests for Foamed Plastics Used for Decorative Purposes

This standard evaluates the flammability and smoke production of foamed plastics used in decorative applications, including stage scenery.

Detailed Explanation of Answer Choices:

Option A (Correct): UL 1975 is the required test standard for foamed plastics used in stage scenery, ensuring compliance with IFC 807.4.2.

Option B (Incorrect): NFPA 11A deals with foam-water fire suppression systems, not foamed plastics for decorative use.

Option C (Incorrect): CPSC 16CFR relates to consumer product safety regulations but does not address fire safety for foamed plastics on stage scenery.

Option D (Incorrect): ASTM D 1784 is a test for rigid PVC plastics and does not apply to foamed plastics used for stage scenery.

Thus, the correct and verified answer is: A. UL 1975.

 Reference to Ventilation Requirements for Flammable Liquids:

The International Fire Code (IFC 2021), Section 5004.3.7.3, and NFPA 30 (Flammable and Combustible Liquids Code), Section 18.5.4.1 specify the ventilation requirements for the use, dispensing, and mixing of flammable liquids in open systems.

Continuous mechanical ventilation must be provided at a minimum rate of 2 CFM per square foot of floor area.

 Reason for Ventilation Requirements:

Flammable liquids release vapors that can ignite at low concentrations, creating fire and explosion hazards.

Proper ventilation removes vapors to prevent them from reaching flammable limits in the air.

 Clarification of Incorrect Answer Choices:

A. 1 CFM per sq. ft. → Incorrect

Too low to effectively control flammable vapor accumulation.

C. 3 CFM per sq. ft. → Incorrect

While more ventilation can be beneficial, the minimum required by code is 2 CFM per sq. ft.

D. 4 CFM per sq. ft. → Incorrect

Exceeds the code-mandated minimum requirement, though higher ventilation rates may be required based on specific hazards.

 Conclusion:

The correct and verified answer is B (2 CFM per sq. ft.), based on IFC 5004.3.7.3 and NFPA 30 Section 18.5.4.1, ensuring safe handling of flammable liquids in open systems.

 Reference to LP-Gas Tank Separation Requirements:

The International Fire Code (IFC 2021), Table 6104.3, provides minimum separation distances for above-ground LP-gas tanks based on capacity and proximity to each other or property lines.

According to Table 6104.3, for an LP-gas tank with a 501-gallon capacity located near a 250-gallon tank, the required minimum separation distance from adjoining property is 10 feet.

 Why Separation Distance is Important:

LP-gas is highly flammable, and inadequate separation distances increase the risk of fire spread and explosion hazards.

Proper spacing ensures safety for occupants, emergency responders, and nearby properties.

 Clarification of Incorrect Answer Choices:

A. 5 ft. → Incorrect

Too close per IFC 6104.3; does not meet safety requirements.

C. 20 ft. → Incorrect

20 feet is required for larger tanks, but not for the combined 501-gal. and 250-gal. tank setup.

D. 25 ft. → Incorrect

Greater than the required minimum; while more distance is safer, IFC mandates a minimum of 10 feet.

 Conclusion:

The correct and verified answer is B (10 feet) based on IFC 6104.3, ensuring safe LP-gas tank separation from adjoining properties.

Retention of Fire Code-Related Records

According to the International Fire Code (IFC) 2021, Section 104.6, records related to code enforcement decisions, including modifications or substitutions (such as a sprinkler system replacing a second exit), must be retained for as long as the building and the condition exist.

This ensures that future inspections, property owners, and authorities can verify past decisions and compliance history.

2. Why the Records Must Be Retained Permanently

Modifications that impact life safety (such as exit requirements) must remain on record for the lifetime of the building to ensure ongoing compliance and safety.

If the condition (sprinkler substitution for an exit) still exists, any future inspector or building official must be able to verify the original approval and rationale.

3. Verification of Other Options

Option A (Five years) – Incorrect, as fire code modifications must remain on record permanently if they affect egress or fire protection systems.

Option B (Three years) – Incorrect, as this timeframe applies to temporary inspection reports, not major code modifications.

Option C (Until the building is sold) – Incorrect, as ownership changes do not affect the need for record retention on fire safety decisions.

Reference Sources:

International Fire Code (IFC) 2021 – Section 104.6 (Fire Code Record Retention Requirements)

NFPA 1: Fire Code (Retention of Code-Related Decisions)

ICC Fire Inspector II Study Guide (2021)

Thus, the correct and verified answer is: D. For as long as the building and the condition exist. ✅

The storage of flammable medical gas supply cylinders inside a building is regulated by 2021 International Fire Code (IFC) Section 5306 – Medical Gas Systems.

IFC Section 5306.2.1 – Storage of More Than 200 Cubic Feet of Medical Gases:

When the quantity of flammable medical gas exceeds 200 cubic feet, it must be stored in a separate room with a minimum 2-hour fire-resistance rating.

The room must also comply with ventilation and explosion control requirements per NFPA 99 (Healthcare Facilities Code).

Why Other Options Are Incorrect?

A. 1/2-hour – Insufficient fire resistance for high-risk gas storage.

B. 1-hour – Does not meet the minimum 2-hour requirement set by the IFC.

D. 3-hour – Exceeds the minimum required by code; the correct requirement is 2-hour fire-resistive construction.

 Reference to Fire-Flow Requirements for Type IIB Buildings:

The International Fire Code (IFC 2021), Appendix B, Table B105.1(2) establishes the minimum fire-flow requirements for buildings based on construction type, size, and the presence of sprinkler systems.

For a 75,000 sq. ft. Type IIB (non-combustible, unprotected) building without sprinklers, the required fire-flow is 5,500 gpm for 4 hours.

 Why Fire-Flow Matters:

Fire-flow ensures that sufficient water is available to control and extinguish fires in large buildings.

Type IIB buildings lack built-in fire resistance enhancements, making adequate fire-flow crucial.

 Clarification of Incorrect Answer Choices:

A. 3,000 gpm for 3 hours → Incorrect

Too low for a building of this size and construction type.

B. 4,000 gpm for 4 hours → Incorrect

Below the required 5,500 gpm per IFC Appendix B.

D. 5,750 gpm for 4 hours → Incorrect

Slightly above the requirement but not the exact minimum mandated by IFC Table B105.1(2).

 Conclusion:

The correct and verified answer is C (5,500 gpm for 4 hours) as per IFC Appendix B, Table B105.1(2), ensuring compliance with fire-flow standards for Type IIB buildings without sprinklers.

LP-Gas Storage Limits for Dealers in Non-Public Buildings

According to the International Fire Code (IFC) 2021, Section 6109.9, the maximum allowable quantity of LP-gas in containers stored by a dealer awaiting resale in a building that is not open to the public is 2,000 pounds of water capacity.

This limit is intended to reduce fire and explosion hazards in enclosed spaces while allowing reasonable storage for commercial purposes.

2. Understanding Water Capacity vs. Propane Weight

The water capacity of an LP-gas cylinder refers to the total weight of water the container can hold, not the actual propane content.

The propane content is typically about 42% of the water capacity (i.e., 2,000 lbs. of water capacity is approximately 840 lbs. of propane).

3. Verification of Other Options

Option A (735 lbs.) – Incorrect, as IFC allows a significantly higher storage limit for dealers in non-public buildings.

Option B (1,000 lbs.) – Incorrect, as the actual limit per IFC 6109.9 is 2,000 lbs.

Option D (2,500 lbs.) – Incorrect, as this exceeds the IFC's maximum allowable storage limit.

Reference Sources:

International Fire Code (IFC) 2021 – Section 6109.9 (LP-Gas Storage Limits in Buildings Not Open to the Public)

NFPA 58: Liquefied Petroleum Gas Code (LP-Gas Storage and Handling Guidelines)

ICC Fire Inspector II Study Guide (2021)

Understanding Construction Types

The International Building Code (IBC) Chapter 6 classifies building construction types based on material combustibility and fire resistance.

Type II construction is noncombustible, meaning it is built using materials such as steel or concrete that do not contribute fuel to a fire.

The difference between Type IIA and Type IIB is the level of fire resistance.

2. Fire Resistance Rating Requirement

Type IIA construction requires a minimum 1-hour fire-resistive rating for structural elements, meeting the conditions in the question.

Type IIB, on the other hand, has no minimum fire-resistive rating for structural components, making it less protective than Type IIA.

3. Verification of Other Options

Option B (IIB) – Incorrect, as Type IIB has no fire-resistive rating for its structural elements and does not meet the 1-hour requirement.

Option C (IIIB) – Incorrect, as Type III allows combustible exterior materials and is not entirely noncombustible.

Option D (VA) – Incorrect, as Type V construction is wood-framed and does not meet the requirement for noncombustible materials.

Reference Sources:

International Building Code (IBC) 2021 – Chapter 6 (Types of Construction)

NFPA 220: Standard on Types of Building Construction

ICC Fire Inspector II Study Guide (2021)

Fire-Resistance Rating for Nonbearing Walls in Type IV Construction

Type IV (Heavy Timber) construction, as defined by the International Building Code (IBC) 2021, Section 602.4, consists of large, solid or laminated wood members.

Interior nonbearing walls and partitions in Type IV construction are not required to have a fire-resistance rating (0 hours) unless they separate different occupancies or are specifically mandated by another code provision.

2. Why Type IV Does Not Require a Rating for Nonbearing Walls

The heavy timber components inherently provide fire resistance due to their large cross-section, which chars on the surface and slows fire penetration.

IBC Table 601 confirms that interior nonbearing walls in Type IV construction do not have a required fire-resistance rating.

3. Verification of Other Options

Option B (1 hour) – Incorrect, as Type IV does not require a 1-hour rating for interior nonbearing walls unless specific conditions apply.

Option C (1-1/2 hours) – Incorrect, as there is no code requirement for this level of rating in Type IV nonbearing walls.

Option D (2 hours) – Incorrect, as Type IV walls are not rated unless separating occupancies.

Reference Sources:

International Building Code (IBC) 2021 – Section 602.4 (Type IV Construction Requirements)

IBC Table 601 (Fire-Resistance Ratings for Building Elements)

ICC Fire Inspector II Study Guide (2021)

In organic coating processes where Class I liquids are exposed to air, fire codes require Class I, Division I electrical installations in hazardous locations to prevent ignition of flammable vapors.

The "immediate vicinity" around pumps or equipment where vapors may accumulate extends 10 feet horizontally from the vapor liberation point in all directions.

Reference to Fire Inspector Documentation:

1. 2021 International Fire Code (IFC) – Section 1503.2.1 (Electrical Installations in Organic Coating Processes)

IFC 1503.2.1 requires that electrical components must be rated for Class I, Division I within 10 feet of vapor sources.

This prevents ignition hazards in locations with flammable vapors.

2. NFPA 33 – Standard for Spray Application Using Flammable or Combustible Materials (2021 Edition) – Section 6.5.2

NFPA 33, Section 6.5.2 states that a 10-foot horizontal zone is considered hazardous and requires Class I, Division I electrical installation.

Detailed Explanation of Answer Choices:

Option A (Incorrect): 5 feet is too short and does not provide sufficient protection from vapor migration.

Option B (Correct): 10 feet is the correct required distance per IFC 1503.2.1 and NFPA 33.

Option C (Incorrect): 20 feet is beyond the required hazardous zone.

Option D (Incorrect): 50 feet is excessive and not required by code.

Thus, the correct and verified answer is: B. 10.