NFPA 10 — Standard for
Portable Fire Extinguishers

To be a true professional, you must realize that NFPA 10 is just one piece of a much larger puzzle. Chapter 2 lists every document considered a mandatory part of the requirements. When NFPA 10 points to one of these, that rule becomes just as legally binding as if it were written directly in the manual.

XIV. NFPA Publications Network

The NFPA has a code for almost every hazard imaginable. When dealing with specific environments, NFPA 10 will "phone a friend" by referencing other standards. Notice that even though we are in the 2026 edition of NFPA 10, it references specific editions of other codes (like the 2024 or 2025 versions). You must use the specific year mentioned to remain compliant.

XV. "Outside" Authorities: Other Publications

• UL (Underwriters Laboratories): The gold standard for testing. Codes like UL 711 (Rating and Fire Testing) and UL 299 (Dry Chemical Extinguishers) define how equipment actually performs.
• CGA (Compressed Gas Association): Since extinguishers are high-pressure cylinders, the NFPA defers to the CGA for rules on how to safely pressure-test and handle gas (like Nitrogen in CGA G-10.1).
• ASTM International: Provides precise scientific testing for things like electrical conductivity (important for not getting shocked when using an extinguisher).

XVI. Government & Global Standards

• DOT — Title 49 CFR: Regulates how high-pressure cylinders are requalified and marked. If the DOT says a tank is expired, it's expired.
• UN — GHS (Globally Harmonized System): Referenced to ensure that chemical labels and safety data sheets are consistent worldwide.

Professional's Resource Map

This chapter establishes the "ground rules" for how specific terms are used throughout NFPA 10. Clear definitions ensure that inspectors, business owners, and AHJs are all speaking the same language.

Official NFPA Designations

Fire Extinguisher Agents and Chemicals

Maintenance and Technical Terms

Types of Extinguishers

4.1 Listing and Labeling

All portable fire extinguishers used to meet this standard must be officially listed and labeled. They are required to meet or exceed the performance and fire testing criteria of UL 711 or CAN/ULC-S508. Additionally, specific types must adhere to their respective standards:

Each unit must be clearly marked with the identifying organization, the product category, its specific fire classification, and the performance standards it has passed. Extinguishers made before January 1, 1986 are exempt from these specific marking rules. Halon units listed under UL 1093 remain compliant as long as they are maintained according to this standard. Any organization providing these listings must use a third-party certification program that meets UL 1803 (unless accredited by the Standards Council of Canada).

4.1.4 Electrical Conductivity

Any extinguisher labeled with a Class C rating must not use an extinguishing agent that conducts electricity. Water-based agents seeking a Class C rating must undergo specialized testing (ASTM D5391). If the agent's conductivity exceeds 1.00 μS/cm at 25°C (77°F), it is considered a conductor and cannot be rated for Class C fires.

4.2 Content Identification

Every extinguisher must have a visible label, tag, or stencil providing the following details:

• The product name as listed on the manufacturer's Safety Data Sheet (SDS)
• Hazardous material identification (HMIS or GHS)
• A list of any hazardous materials exceeding 1.0% of the contents
• A list of each chemical exceeding 5.0% of the contents
• Specific hazard warnings regarding the agent
• Contact information for the manufacturer or service provider

4.3 Instruction Manual

The owner must be provided with a manual that includes condensed instructions and warnings for installing, operating, inspecting, and maintaining the equipment. This manual must cite NFPA 10 as the primary source for selection and placement requirements.

4.4 Obsolete Fire Extinguishers — Must Be Removed from Service

5.1 General Requirements

The process of selecting the right fire extinguisher for a specific location is governed by the detailed rules found in sections 5.2 through 5.5.5. Critical factors to weigh include: the category and scale of the most probable fire, the specific dangers present in that spot, whether there is energized electrical gear nearby, the local temperature (ambient conditions), and other specialized factors listed in the annex.

These portable units are strictly designed as the "first line of defense" to handle fires that are still small or limited in scope. Even if a building features high-end automated protection like sprinklers or standpipe hose stations, you are still required to provide portable extinguishers independently of those systems.

5.2 & 5.3 Fire Classification System

All fire risks must be sorted into one of five standard categories. For Class A and B, the letter must be preceded by a rating number. Class C, D, and K do not use these numbers; they only use the letter to indicate suitability.

5.4 Categorizing Occupancy Hazards

5.5 Rules for Specific High-Risk Scenarios

5.5.1–5.5.3 Multiple Ratings

If an extinguisher has multiple ratings (like a 4-A:80-B:C), it can be used to satisfy the requirements for each of those categories. You must protect the building itself (Class A) and the specific occupancy hazards (A, B, C, D, or K) regardless of any existing fixed suppression systems.

5.5.4.1–5.5.4.3 Specialized Fires

• Pressurized Liquid/Gas: If protecting against fires where liquids are under pressure (sprayed or pumped), use a large-capacity dry chemical unit (10 lb or more) with a discharge rate of at least 1 lb per second.
• Three-Dimensional Fires: For fires involving falling or gravity-fed liquids (like a leaking tank), the same 10 lb / 1 lb-per-second rule applies.
• Obstacle Fires: To fight a fire where a physical object blocks the stream, you need either a vapor-suppressing foam agent or multiple Class B units used simultaneously.

5.5.4.5 Kitchens

Use extinguishers specifically labeled for Class K. If the unit was made after 2002, it cannot have an "extended wand" nozzle. If the kitchen has an automatic hood system, post a sign near the extinguisher telling the operator to activate that system before using the portable unit.

5.5.4.6–5.5.4.7 Sensitive Areas

6.1 General Installation Guidelines

6.1.1 Quantity of Units

The total number of extinguishers required for a property is determined by the specific criteria in this chapter. This requirement is independent of any existing automatic sprinkler systems, standpipes, hoses, or other fixed fire protection equipment. You are always permitted to install additional extinguishers beyond the minimum requirements.

• 6.1.1.3 Low-Rated Units: You can install extinguishers with lower ratings than those in the hazard tables, but they do not count toward the minimum legal requirements for the building.
• 6.1.1.4 Multiple Hazard Labeling: When different types of extinguishers are grouped together to protect various hazard classes, each unit must be accompanied by a clear placard or sign indicating its specific fire-fighting purpose or protection rating. Signs must be placed either directly above or next to the extinguishers. If in a cabinet, the sign can be on the door as long as it doesn't hide the unit or interfere with fire resistance.

6.1.2 Operational Readiness

Every portable extinguisher must be kept fully charged and in working order. They must remain in their designated locations at all times when not being used.

6.1.3 Strategic Placement

Extinguishers must be located where they are easily visible, readily accessible, and available for immediate use. They should be positioned along common walking paths, particularly near exits.

6.1.3.3 Visibility and Signage

• Units must be visible to everyone in the area.
• If a room's layout creates visual obstructions, you must use signs or markers to point out where the extinguisher is.
• If a unit is inside a cabinet, it must remain visible, or the cabinet must be marked with its location.
• Any signs used must be clearly visible from the normal path of travel and must be in close proximity to the extinguisher.

6.1.3.4 Mounting Standards

All non-wheeled extinguishers must be installed using one of these four approved methods:

1. A hanger specifically intended for that model
2. A bracket with releasing straps or bands provided by the manufacturer
3. A listed bracket approved for this specific use
4. An approved wall recess or cabinet

6.1.3.9 Installation Height Requirements

6.1.3.10 Labeling and Instructions

Extinguishers must be installed with the operating instructions facing outward. Maintenance tags, HMIS labels, and hydrostatic test labels must be placed on the sides or back — never on the front of the unit.

6.1.3.11 Cabinet Regulations

• Locking: Cabinets generally must not be locked unless the area is prone to vandalism or malicious use, and even then must have an emergency access feature.
• Break-Fronts: If the cabinet has a panel that must be broken, a breaker bar or hammer must be attached.
• Visibility: Cabinets must be visible from the path of travel. If in a wall recess, the extinguisher must be placed so instructions face outward.
• Fire-Rated Walls: Only surface-mounted or listed fire-rated cabinets can be installed in fire-resistance-rated walls.
• External Use: Units stored outside must be protected from extreme temperatures as indicated on their labels.

6.1.4 Antifreeze and Systems

Water extinguishers must be protected down to −40°F (−40°C) using the antifreeze stipulated on the nameplate. Calcium chloride solutions cannot be used in stainless steel units. If an electronic monitoring system is used, it must be continuously supervised for both integrity and power.

6.2 Class A Hazard Installations

The minimum size for Class A extinguishers is based on Table 6.2.1.1. The total number of units is determined by dividing the total floor area by the maximum area one unit is allowed to protect. Maximum travel distance: 75 ft (22.9 m).

• Combining Ratings: Two 1-A water extinguishers can meet a 2-A requirement, or two 2.5-gallon units can meet a 4-A requirement.
• Hose Stations: In some buildings, up to half of the required extinguishers may be replaced with 1.5-inch hose stations, provided they are spaced evenly and meet NFPA 14 standards.

See Table 6.2.1.1 in the NFPA standard for complete sizing criteria for Class A hazards, including mandatory minimum ratings, maximum area per unit, and maximum travel distances.

6.3 Class B Hazard Installations

Minimum ratings are dictated by Table 6.3.1.1. You cannot use multiple small extinguishers to "add up" to a required Class B rating (except for foam units as specified).

• Foam Exception: Up to three foam units can be used together to meet Class B requirements for extra hazards.

6.3.2 Flammable Liquids of Appreciable Depth

6.4–6.7 Class C, D, and K Requirements

6.7 Solid-Fuel Cooking

For wood or coal fire boxes up to 5 cubic ft, provide either a 2-A water unit or a 1.6-gallon Class K wet chemical unit.

7.1 General Provisions

7.1.1 Responsibility

The legal obligation to handle inspection, upkeep, and refilling of fire extinguishers is placed on the property owner, their designated representative, or the person currently occupying the space where the equipment is installed.

7.1.2 Personnel Requirements

• 7.1.2.1 Certification: Any person who performs technical maintenance or recharging on fire extinguishers is required to be officially certified.
• 7.1.2.1.1 Training Supervision: If an individual is in training for certification, they are permitted to perform maintenance and recharging tasks only if under the direct, physical supervision and immediate presence of a certified professional.
• 7.1.2.1.2 Testing Standards: To obtain certification, an individual must successfully pass an examination administered by an organization the AHJ finds acceptable.
• 7.1.2.1.3 Exam Scope: At minimum, the certification test must evaluate knowledge of the specific chapters and supplementary annexes of this standard.
• 7.1.2.1.4 Use of Standard: During testing, candidates are permitted to use the NFPA 10 standard as a reference.
• 7.1.2.1.5 Issuance: Individuals who pass the required exam shall be provided with a formal document or certificate of completion.
• 7.1.2.1.6 Availability: This certificate must be made available for review whenever the AHJ requests to see it.
• 7.1.2.2 Resources and Training: Those performing maintenance and recharging must have the manufacturer's service manuals, correct professional tools, appropriate recharging materials and lubricants, and exact replacement parts (or parts listed for that specific model) on hand.
• 7.1.2.3 Inspection Exception: Personnel who only conduct routine inspections are not required to hold the technical certification described above.

7.1.3 Replacement Fire Extinguishers

Whenever an extinguisher is pulled from its installed spot for service, it must be replaced immediately with a unit suitable for the specific hazards in that area and with a rating at least equal to the one being removed. The property owner or their agent must be informed whenever extinguishers are removed or replaced.

7.1.4 Use of Tags and Labels

• Tags or stickers for recording inspection, maintenance, or recharging history must not hide operating instructions, fire classification symbols, or manufacturer's labels.
• Labels showing the extinguisher's classification or specific fire-fighting use may be placed on the front of the tank.

7.2 Inspection Procedures

7.2.1 Frequency of Inspection

7.2.2 Inspection Checklist

7.2.1.2.1 Method Selection and Approval

The property owner determines whether to use manual inspection, electronic monitoring, or both. Any inspection method other than manual requires AHJ approval. Units in areas with high fire frequency, severe hazards, risk of physical damage, or corrosive environments must undergo the extra visual checks in §7.2.2.4.

7.2.3 Immediate Corrective Action

7.2.4 Records of Inspection

• Manual records must be kept on a tag or label on the unit, a checklist, or in a digital file. They must list the month/year of the check and the initials of the inspector.
• Records must include every extinguisher checked, including those needing repairs.
• You must keep records proving the last 12 monthly inspections were performed.
• Electronic monitoring systems must keep logs for any unit needing corrective action and records proving the last 12 monthly checks were done.

7.3 Maintenance Procedures

7.3.1 Procedures and Intervals

Maintenance is a thorough check of the mechanical parts, agent, expellant, and physical shell. You must follow the manufacturer's service manual. Maintenance must be done every year, during a hydrostatic test, or if an inspection reveals a problem.

7.3.2 Annual External Examination Checklist

7.3.3 Internal Examination Intervals

See Table 7.3.3.1 in the NFPA standard for the complete list of extinguisher types and mandatory maximum intervals for internal examinations. Key rules:

• 7.3.3.2 Loaded Stream: These can be re-used if the agent is analyzed according to manufacturer instructions.
• 7.3.3.3 Cartridge/Cylinder: Must be internally examined every year.
• 7.3.3.4 Wetting Agents: Must be disassembled and serviced annually.
• 7.3.3.5 Pump Tanks: Must be internally checked every year.
• 7.3.3.6 Nonrechargeable: Annual internal checks aren't required for nonrechargeable CO₂, Halon, or stored-pressure units unless specified in §7.3.3.2.

7.3.4 Annual Maintenance Records

Every unit must have a secure tag or label showing the month/year of service, the person who did the work, and their agency.

7.3.4.2 Verification-of-Service Collar

Every unit that has an internal exam or is recharged by removing the valve must have a collar around its neck. Exceptions: cartridge units, pump tanks, or CO₂ units recharged without valve removal.

7.3.6 Six-Year Internal Exam

• Every 6 years, stored-pressure dry chemical units requiring a 12-year hydrostatic test must be emptied and serviced.
• Halon recovery must use a listed closed recovery system.
• Nonrechargeable units (except Halon) must be removed from service after 12 years.
• Units passing a 6-year check must have a 2 in. × 3.5 in. (51 mm × 89 mm) weatherproof label attached by a heatless process, showing date, technician, and agency.

7.4–7.7 Specialized Maintenance

• 7.4 CO₂ Hose Conductivity: All CO₂ hose assemblies must undergo a conductivity test every year. Those that fail must be replaced. A weatherproof label (0.5 in. × 3 in.) must be attached to those that pass.
• 7.5 Hose Stations: Must be maintained per NFPA 1930.
• 7.6 Electronic Monitoring: Must be tested annually including power supplies, sensors, and communication. 100% of units must be verified during initial setup and every year after.
• 7.7 Wheeled Units: Discharge hoses must be completely uncoiled and checked for damage every year. They must be re-coiled per manufacturer instructions. Pressure regulators must be tested annually for static pressure and flow rate.

7.8 Recharging and Agents

7.8.1 General Recharging

• All rechargeable units must be refilled after any use or when required. The amount must be verified by weighing.
• 7.8.1.3.4 Leak Tests: After recharging, a leak test is required on all stored-pressure and self-expelling units.
• 7.8.1.3.5 Hydrostatic Rule: No unit can be recharged if it's past its hydrostatic test date.

7.8.2 Frequency

Pump tanks and wetting agent units must be recharged every 12 months. Foam units must be recharged per manufacturer instructions (not exceeding 5 years).

7.8.3 Recharge Agents

• Use only the agent specified on the nameplate.
• Mixing multipurpose dry chemicals with alkaline-based chemicals is strictly forbidden.
• 7.8.3.3 Topping Off: Dry chemical can only be re-used if checked for contamination.
• 7.8.3.4 Recovery Systems: Re-using dry chemical requires a closed recovery system. Halon must use a listed closed recovery system.
• 7.8.3.9 CO₂ Quality: The vapor phase must be at least 99.5% CO₂.
• 7.8.3.10 Water Types: Recharging must use exact measurements by weight or volume, or fill marks.

7.8.4 Expellant Gas

Only industrial-grade nitrogen (−60°F dew point) is allowed for dry chemical and Halocarbon units. Halon requires argon with a −65°F dew point. Compressed air is only allowed if passed through a moisture-trap system. Recharging must be recorded on a tag showing the date, person, and agency.

7.9–7.14 Finishing Requirements

• 7.9 Pressure Gauges: Broken, cracked, or nonworking gauges must be replaced with the correct gauge for that agent and valve body material.
• 7.10 Cabinets: Missing breaker bars or damaged/broken panels must be replaced.
• 7.11 Signage: All placards identifying hazards or classes must be kept legible.
• 7.12 Conversion Prohibited: You cannot use an extinguisher for anything but fire protection, and you cannot convert a unit from one agent to another.
• 7.13 Service Collars: Must be single, uninterrupted circular pieces that cannot be removed without taking the valve off. New units, Halon/CO₂ recharged without valve removal, and cartridge units are exempt.
• 7.14 Weight Scales: Scales used for service must have the reading increments and accuracy needed to verify the weights on the nameplate.

8.1 General Provisions

• 8.1.1 Testing Mandate: All pressure vessels utilized as fire extinguishers, along with specific components identified in this standard, must undergo hydrostatic testing as detailed throughout this chapter.
• 8.1.2 Regulatory Compliance: Any cylinders or cartridges that carry U.S. DOT or Transport Canada (TC) specifications must be requalified and tested in strict accordance with those governing bodies.
• 8.1.3 Inspection Scope: A hydrostatic test is never a standalone procedure; it must always include a thorough internal and external visual examination of the cylinder.
• 8.1.4 Testing Medium: Tests must be conducted using water or another compatible non-compressible fluid. Using air or other gases as the only medium for pressure testing is strictly prohibited. All air must be completely vented from the cylinder before testing begins.
• 8.1.5 High-Temperature Exposure: If an aluminum cylinder or shell is suspected of being exposed to heat exceeding 350°F (177°C), it must be removed from service and subjected to a hydrostatic test immediately.

8.1.2.1 Qualified Personnel

• Only individuals with proper training in pressure testing safety and procedures are permitted to perform hydrostatic tests. These individuals must comply with §7.1.2 requirements and must have the necessary testing equipment, dedicated facilities, and appropriate manufacturer service manuals available.
• 8.1.2.1.1 Certification: Personnel must be certified by an organization maintaining a program approved by the AHJ.
• 8.1.2.1.2 Facility Credentials: Facilities holding a DOT Requalification Identification Number (RIN) or TC certification are authorized to perform hydrostatic testing without needing further certification as an extinguisher technician under §7.1.2.
• 8.1.2.1.3 Subcontracting: If hydrostatic testing is outsourced to a certified facility, a technician who meets §7.1.2 standards must still handle assembly and disassembly of valves and cylinders, any parts replacement, and all other related service work.

8.2 Test Equipment Standards

8.3 Frequency Requirements

Hydrostatic retesting must occur at intervals not exceeding those listed in Table 8.3.1. This retest must be completed within the same calendar year as the specified interval. See Table 8.3.1 in the NFPA standard for the exhaustive list.

8.4 Cylinder Examination and Condemnation

8.4.1 General Weakness

If an extinguisher shows signs of dents, corrosion, or mechanical damage that suggests structural weakness, it must either be condemned or retested immediately.

• 8.4.1.2 Nonrechargeable Units: If a non-Halon disposable unit shows these signs, it must be discharged and thrown away. For nonrechargeable Halon units, they must be returned to a dealer or manufacturer for gas recovery without being discharged.

8.4.2 Mandatory Condemnation Criteria

A cylinder must be destroyed and cannot be tested if it meets any of the following:

8.5 Testing Procedures

• 8.5.1 General Protocol: The test pressure must be held for at least 30 seconds, and long enough to allow for a full visual check and cylinder expansion. Before filling with water, all valves, hoses, and internal parts must be removed and the unit emptied (with specific exceptions for cartridge-operated units). A full internal and external visual check per §8.4.2 must be done before any water is added.
• 8.5.2 Low-Pressure Cylinders: Technicians must remove the gas cartridge/receiver and replace the valve with a test bonnet. Any distortion or a drop in pressure on the test gauge is grounds for immediate condemnation. After passing, the unit must be dried at a temperature not exceeding 150°F (66°C).
• 8.5.4 Hose Assemblies: Couplings must be marked, and the discharge valve removed. The hose must be filled with water and placed in a protective cage. Pressure must be reached within 1 minute and held for at least 1 minute. Any leakage, distortion, or permanent movement of the couplings constitutes a failure.

8.6 Test Pressures

8.7 Recording and Labeling

• 8.7.1 Retention: Records must be kept by the testing organization until the next test is due or the period expires.
• 8.7.2 Low-Pressure Labels: Passing units require a label (minimum 2 in. × 3.5 in.) attached by a heatless process. It must be weatherproof, self-destructing if removed, and include: month and year of test (perforated), test pressure used, and initials/name of the technician and agency.
• 8.7.3 High-Pressure Stamping: These units must be stamped with the RIN, month, and year on the shoulder, head, or neck.

8.8 Condemning Extinguishers

• 8.8.1 Written Notice: If a unit fails, the technician must notify the owner in writing that the cylinder is condemned and cannot be reused. Repairs are strictly forbidden.
• 8.8.2 Marking — Spec Cylinders: Stamp a series of "X"s over the DOT/TC specification and service pressure, or stamp "CONDEMNED" on the shoulder/head with at least ¼ inch tall letters.
• 8.8.2 Marking — Non-Spec Cylinders: Label as "CONDEMNED." These markings must never be removed or hidden.
• 8.8.3 Disposition — Spec Cylinders: Handled per DOT/TC rules. Non-spec units must be rendered unusable by puncturing, drilling, cutting in half, or destroying the threads.

Annex A — Explanatory Material

A.1 The Success Factors for Portable Extinguishers

Portable extinguishers are only one part of a fire protection plan. For them to work effectively, four conditions must be met:

1. The unit must be in working order and located according to Chapter 6.
2. The agent must be the right type for the specific fire (Class A, B, C, D, or K).
3. The fire must be caught while it is still small enough for a portable unit to handle.
4. The person discovering the fire must be ready, willing, and able to use the extinguisher.

A.2 Understanding Authorities and "Approval"

• The NFPA's Role: The NFPA does not "approve" or "certify" specific brands or installations.
• The AHJ: Fire marshals, insurance inspectors, etc., are the final word. They base their acceptance on the owner's compliance with standards and the listings provided by testing labs like UL.
• Listed vs. Labeled: Not all organizations recognize a product as "listed" unless it also carries a physical label from the testing organization.

A.3 Agent Characteristics & Behavior

• Carbon Dioxide (CO₂): It is 1.5 times heavier than air. It works by diluting the oxygen around the fire. When released, it forms a "snow" (dry ice) that can be extremely cold.
• Dry Chemical vs. Dry Powder: Annex A clarifies a common point of confusion. Dry Chemical is for Class A, B, or C fires. Dry Powder is strictly for combustible metal (Class D) fires.
• AFFF & FFFP (Foams): These create a physical barrier that excludes oxygen and suppresses fuel vapors. They are generally compatible with dry chemicals for combined use.
• Halon & Halocarbons: These are "Clean Agents" that leave no residue. Halon production ceased in 1994 due to the Montreal Protocol, but existing units are still legal to maintain and use as long as they meet UL 1093.

A.4 The 1984 Standards Evolution

A significant portion of the Annex explains why many extinguishers made prior to 1984 are now obsolete. The 1984 edition of UL 299 introduced major safety improvements:

• Hoses: All units rated 2-A or 20-B and higher were required to have discharge hoses to allow the user to stand upright and direct the stream accurately.
• Discharge Time: 2-A units were required to have at least a 13-second discharge duration (up from 8 seconds) to improve the success rate for novice users.
• Ease of Use: Pictograms were standardized, and the force required to pull a safety pin was capped at 30 lbs.

A.5 Maintenance and Recharging Safety

• Venting Pressure: Never attempt to remove a valve body without first verifying all pressure is vented. Pressure-indicating devices (gauges) can malfunction and show "zero" even when the tank is still dangerous.
• Moisture is the Enemy: In non-water extinguishers, moisture causes dry chemicals to "cake" and become unusable. It also creates a severe corrosion hazard inside the shell.
• Aluminum Integrity: If an aluminum shell is exposed to fire or heat over 350°F (177°C), its structural strength is permanently reduced. These units must be condemned or hydrotested immediately.
• Verification-of-Service Collars: These provide visual proof that the valve was actually removed and the unit was opened for service. The date on the collar should always match or be more recent than the maintenance label.

A.6 Hazard Occupancies & Installation

• Light Hazard: Offices, classrooms, and churches where the fuel load is low.
• Ordinary Hazard: Retail shops and light manufacturing.
• Extra Hazard: Woodworking, vehicle repair, and cooking areas where fires can spread rapidly.
• Vented Cabinets: In high-heat areas, vented cabinets with tinted glass can lower the internal temperature of the extinguisher by 10°F to 15°F.

A.7.3.1 Key Maintenance Checklists

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Annex B — Recommended Markings to Indicate Extinguisher Suitability

B.1 General Labeling Requirements

• Durability: Labels should be decals resistant to color fading and designed to withstand the environment they are placed in.
• Placement: Markings should be on the front of the extinguisher shell.
• Legibility: A person should be able to clearly read the label from a distance of 3 feet (1 meter). If the markings are placed on a wall panel near the extinguisher, they must be legible from 15 feet (4.6 meters).

B.2 The Pictorial Marking System (Modern Standard)

The modern system uses icons to represent different fire hazards, designed to bridge language barriers and provide instant recognition. The symbols are white on a blue background for "YES" (suitable uses). If an extinguisher is dangerous to use on a certain fire, the icon will typically be shown with a red slash through it. Standard pictograms:

• Class A (Trash, Wood, Paper): A burning trash can and wood pile.
• Class B (Liquids): A tilted gas can pouring over a fire.
• Class C (Electrical): An electrical cord and plug next to a flame.
• Class K (Cooking): A frying pan on fire.

B.3 The Letter-Shape Symbol System (Legacy Standard)

B.4 Technical Color Specifications (Pantone Matching System)

• Blue: PMS 299 or Process Blue
• Red: Warm Red or 192 Red
• Green: Basic Green
• Yellow: Basic Yellow

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Annex C — Fire Extinguisher Selection

C.1 Core Principles of Selection

Choosing the best portable extinguisher isn't just about the fire class; it requires evaluation of the environment and the people using it. Key factors include the fuel source, environmental extremes (wind, drafts, freezing, high heat), the physical ability and training of the operator, the potential severity and speed of fire travel, and whether the agent will cause adverse chemical reactions or health risks (like oxygen displacement in confined spaces).

C.2 Class B Configurations (Flammable Liquids)

Annex C breaks Class B fires into five distinct types:

• Spill Fires: Horizontal, uncontained liquid on a surface.
• Fuel-in-Depth: Liquids deeper than 0.25 in. (6.3 mm), such as in dip tanks or quench tanks.
• Obstacle Fires: Fires surrounding a large physical object.
• Gravity/Three-Dimensional: Falling, pouring, or dripping fuel. These are notoriously hard to extinguish and often require foam or specialized dry chemicals.
• Pressure Fires: Forced, pumped, or sprayed fuel. Special Caution: Never attempt to extinguish these unless you are certain the fuel source can be shut off immediately.

C.2 Electronic & Specialized Hazards

• Class C (Electrical): Selection depends on how much "agent contamination" the equipment can tolerate. Clean Agents (CO₂ or Halocarbons) are preferred for delicate servers; dry chemicals might be acceptable for heavy industrial motors.
• Class D (Metals): These burn at extreme temperatures. You must use agents specifically listed for the exact metal involved (e.g., lithium chloride for lithium fires).
• Class K (Kitchens): High-efficiency cooking appliances create hotter-burning fires. Only Wet Chemical agents that can "saponify" (create a thick soap-like foam) are recommended to seal out oxygen and prevent re-flash.

C.3 Comparing Extinguishing Agents

C.4 Heavy-Duty Protection: Wheeled Units

Wheeled fire extinguishers are reserved for "extra-hazard" areas or large spaces where one person needs to deliver a massive amount of agent quickly. Models with large rubber tires are better for outdoor terrain; wide-rim wheels work best for indoor aisles. Because of their high pressure and agent volume, these should only be used by operators who have undergone live fire training.

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Annex D — Operation and Use

D.1 The Human Element: Who Operates Extinguishers?

The effectiveness of a fire extinguisher depends heavily on the skill of the person holding it. Annex D categorizes potential users in descending order of probable skill:

1. Trained fire departments (professional municipal or industrial teams)
2. Trained or untrained employees (business or industrial workers)
3. Untrained private owners (people in their homes, cars, or boats)
4. Untrained general public (passersby or customers)

Without training, users often delay action, waste extinguishing agents through poor technique, or fail to put out the fire entirely. Planners must choose equipment based on who is most likely to use it and their expected skill level.

D.2 Five Primary Methods of Operation

• Stored-Pressure: The most common; agent and expellant gas are in a single tank.
• Gas Cartridge or Cylinder: The expellant gas is in a separate container and only pressurizes the shell when the user releases it.
• Self-Expelling: The agent (like CO₂) has enough of its own vapor pressure to push itself out.
• Mechanically Pumped: The user provides the energy by physically pumping a handle.
• Hand-Propelled: The material is applied manually with a scoop or bucket (for some Class D agents).

See Table D.1.2.2 in the NFPA standard for a complete breakdown of which extinguishing agents utilize specific expelling methods.

D.3 The 5-Step Operation Sequence

1. Recognition: Identifying a device as a fire extinguisher.
2. Selection: Ensuring the extinguisher is suitable for the type of fire occurring.
3. Transport: Bringing the unit to the fire. Note: portability is affected by travel distance, stairs, operator physical ability, and room congestion. Large wheeled units require wide aisles and smooth flooring.
4. Actuation: Positioning correctly → removing locking devices → starting discharge → directing agent. (Sub-steps: position unit in intended position [usually upright], pull ring pin or break tamper seal, squeeze lever or turn handle, direct stream at base of flames.)
5. Application: Directing the agent at the fire to put it out.

D.4 Agent Characteristics & Application Techniques

• Water-Type: Best for Class A fires. Aim at the base of flames and move close as fire subsides. Deep-seated fires (like a mattress) need to be "broken apart" and soaked.
• Foam: Best for liquid fires in tanks. Bounce the foam off the back wall of the container to let it float gently across the surface.
• Carbon Dioxide (CO₂): Very short range (3–8 ft). In unventilated spaces, CO₂ can cause oxygen deficiency; operators must be cautious about their own breathing.
• Halogenated Agents: Very effective but can be easily dispersed by wind. Apply from the near edge and sweep toward the back.
• Dry Chemical: Discharged in 8–20 seconds for most units. It's critical to get the application right immediately — there is rarely time for a second attempt. Multi-purpose dry chemical "softens and sticks" to hot surfaces, helping prevent re-ignition but can cause corrosion if not cleaned up.
• Wet Chemical (Class K): Discharged as a fine spray to avoid splashing hot grease. It reacts with the oil to create a thick foam blanket.
• Water Mist: Uses distilled water in a fine spray. Perfect for areas where clean-up is a major concern, like operating rooms or museums.

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Annex E — Distribution

E.1 The Philosophy of "Travel Distance"

In a fire, every second counts. Distribution isn't just about the number of units, but the time it takes for a person to walk from the fire, grab the device, and return. Travel distance is the actual walking path around partitions, through doorways, and around machinery — not a straight-line measurement. While some operations (like welding) need an extinguisher right next to them, most units should be placed along normal paths of travel and near exits.

E.2 General Arrangement in a Building

A physical survey of the property should ensure these eight characteristics are met:

1. Uniform distribution — space evenly so there are no "dead zones"
2. Accessibility — keep free from blocking by storage or equipment
3. Visibility — easy to spot from the normal path of travel
4. Floor-by-floor determination
5. Near exits and paths of egress
6. Near areas of highest risk
7. Protected from damage
8. Appropriate for the specific hazards of that area

E.3 Class A Distribution Strategies

For ordinary combustibles, the standard 75-foot travel rule is the benchmark. Planners use the total floor area and the specific rating of the extinguisher to determine the minimum count. Although a single unit could theoretically protect a massive circular area, buildings are rectangular — this means you often need more extinguishers than the basic math suggests to stay within the 75-foot limit.

See Table E.3.5 for maximum square footage one extinguisher can protect based on its Class A rating and hazard level. See Table E.3.6 for number of extinguishers required based on total building square footage. See Table E.3.7 for comparison of extinguishers needed for single-story vs. multi-story buildings.

E.4 Class B Distribution

Because flammable liquid fires grow much faster, travel distances are significantly shorter — usually 30 to 50 feet. Planners must exercise judgment to place units closer to high-hazard spots (like an auto repair bay) even if the math allows them to be farther away. For deep liquid hazards (dip tanks), distribution is based on providing 2 numerical units of Class B protection per square foot of liquid surface.

E.5 Class C, D, and K Distribution

• Class C (Electrical): Individually judged based on equipment size and whether the operator can de-energize power. Goal: allow the user to fight the fire without risk of electrical shock "arc" reaching them.
• Class D (Metals): Must be within 75 feet of the hazard. Chemistry is critical — using the wrong agent on a metal fire can cause an explosion.
• Class K (Kitchens): Because of the high heat of modern vegetable oils, must be within 30 feet of the cooking appliances.

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Annex F — Selection of Residential Fire Extinguishing Equipment

F.1 Key Definitions for Homeowners

• General Use Residential Extinguisher: Specifically tested and listed for broad use in and around the home (one- and two-family dwellings).
• Special Purpose Residential Extinguisher: Designed for a very specific hazard mentioned on the label (such as a unit dedicated only to stovetop grease fires).

F.2 Minimum Recommendations per Floor

Every floor level should have:

• A single extinguisher rated at least 2-A:10-B:C or higher; or
• One unit rated 2-A or higher plus a second unit rated 10-B:C or higher.

• Attached Garages: At least one 2-A:10-B:C rated extinguisher.
• Detached Garages: Due to the high volume of flammables (gasoline, lawnmowers, paint thinners), installing a larger extinguisher than the minimum home recommendation is suggested.

F.3 Handling Specific Home Hazards

• Electronic Equipment (TVs and Computers): A unit with a 1-B:C rating or higher is recommended, specifically using Carbon Dioxide or Halogenated agents to prevent residue damage.
• Carports: If you have partially open carports where flammable liquids are stored, a residential-grade extinguisher should be provided there as well.

F.4 Installation and Safety Precautions

• Placement: Keep in accessible spots along an escape route, roughly 40 feet (12 meters) of travel distance from the equipment.
• Height: Mount so the top is no more than 5 feet off the floor and the bottom is at least 4 inches off the ground.
• After Use: Even if you only sprayed a tiny burst, the unit must be refilled or replaced immediately. A partially discharged extinguisher will lose its pressure over time and fail when you need it next.

F.5 Responsibility and Maintenance

The homeowner or occupant is legally responsible for the care and use of these devices. Perform a quick visual check every month to ensure the unit is in its place, the pressure is good, and there is no visible damage or corrosion. Rechargeable units should be serviced by competent individuals using the correct tools and parts.

See Table F.7.3.2 in the NFPA standard for a complete breakdown of internal maintenance and hydrostatic testing intervals for residential dry chemical, water, foam, CO₂, and halogenated extinguishers.

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Annex G — Extinguisher Classification and Rating System

G.1 How Ratings Are Determined

Every fire extinguisher is tested at a standard temperature of 70°F (21°C). Ratings are based on the results of planned fires of specific sizes:

• Class A Rating: Tested using wood fuel to see how much of a wood-based fire the unit can kill.
• Class B Rating: Tested using square pans filled with heptane at a 2-inch (51 mm) depth.
• Class C Rating: There is no actual "fire test" for Class C. The focus is on operator safety — the agent is tested to ensure it won't conduct electricity back to the person using the device.
• Class D & K: These involve highly specialized tests on combustible metals or high-heat cooking oils/fats.

G.2 Deciphering the Labels (The Multiplier Effect)

When you look at a label like 4-A:20-B:C, those numbers tell a specific story:

• The Class A Number: A 4-A unit is designed to extinguish approximately twice as much fire as a 2-A unit (roughly equivalent to 2½ gallons of water).
• The Class B Number: A 20-B unit is rated to handle approximately 20 times more liquid fire than a basic 1-B unit.
• The Class C Letter: Indicates the unit is safe to use on energized electrical equipment without shocking the user.

G.3 Historical Context and Environment

The current rating system has been the industry standard since June 1, 1969. Laboratory ratings for Class B fires are often higher when conducted indoors under controlled conditions; units with ratings of 30-B or higher are typically based on more difficult outdoor fire tests. Ratings assume the operator has a certain level of training — a "4-A" rating doesn't guarantee a novice can put out that much fire, but it provides a benchmark for comparing units.

G.4 Specialized Metal and Multiple Ratings

• Class D (Metals): These never have a number assigned. Effectiveness is based on the specific metal they were tested on, which will be listed on the nameplate.
• Combination Units: Most modern extinguishers are effective on more than one class of fire, carrying multiple letters and numbers (e.g., ABC) to show versatility.

See the Table in the NFPA standard for the full list of laboratory-approved ratings for Class A fires (ranging from 1-A to 40-A) and Class B fires (ranging from 1-B to 640-B).

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Annex H — Conditions of Selection

H.1 Physical Conditions Affecting Selection

• Gross Weight: The physical capability of the people expected to use the device must be considered. If a hand-portable unit is too heavy for the staff, wheeled units or fixed systems should be evaluated.
• Corrosive Atmospheres: In environments like chemical plants or coastal areas, extinguishers must be provided with extra protection or constructed of materials that won't degrade.
• Agent Reactions: You must consider if the extinguishing agent will cause an adverse reaction with manufacturing processes or sensitive equipment.
• Mobility and Terrain: For wheeled units, the path of travel is critical. Ensure doorways and aisles are wide enough for the unit to pass, and that the wheel type (rubber vs. wide-rim) matches the floor or ground surface.
• Wind and Draft: In outdoor or high-airflow areas, agents can be blown away before reaching the fire. Selection should favor agents and nozzles with higher range and discharge force to overcome these conditions.

H.2 Health and Safety Conditions

• Confined Spaces: CO₂ and Halon extinguishers can displace oxygen or produce toxic decomposition products. In small, unventilated rooms or vehicles, this can lead to loss of consciousness. Labels, warning signs, and proper training are mandatory for these installations.
• Visibility Issues: When a dry chemical extinguisher is discharged in a small area, the cloud of powder can reduce visibility to near zero for several minutes. This can hinder the operator's ability to find an exit or see if the fire is out.
• Electrical Shock: Extinguishers that are not Class C rated (like water or foam) present a major shock hazard if used on live electrical equipment.

H.3 Dangerous Chemical Reactions

H.4 Performance Characteristics

• Discharge Times: Range from as little as 8 seconds for small dry chemical units to over 2 minutes for large water-based pump tanks.
• Range: Stream ranges vary from a short 3 feet (CO₂) to over 50 feet (wheeled water units).
• Freeze Protection: It is vital to identify which units require heated cabinets or antifreeze charges if stored in temperatures below 40°F (4°C).

See Table H.2 in the NFPA standard for a comprehensive breakdown of every major extinguishing agent, including method of operation, capacity, horizontal stream range, discharge time, and UL/ULC classification.

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Annex I — Maintenance Procedures

I.1 Purpose and Organization

Annex I provides a structured approach to maintenance through two distinct checklists — one for mechanical components (shells, valves, hoses, gauges) and one for agents and expelling means (the extinguishing chemicals and gases).

I.2 Maintenance for Disposable vs. Rechargeable Units

• Rechargeable Units: The checklists provide specific corrective actions (cleaning, lubricating, or replacing parts) to bring the unit back into compliance.
• Disposable (Nonrechargeable) Units: If a checklist reveals a discrepancy, the unit must generally be removed from service and replaced.
• Halon Handling: Disposable Halon units should never be depressurized by the technician. They must be returned to a manufacturer or agent for proper recycling.

I.3 Mechanical Parts Maintenance

Common failure points and their fixes:

• Shell and Cylinder: Looking for corrosion, dents, or illegal repairs (like welding). If the shell's integrity is compromised, the unit is often condemned.
• Pressure Gauges: Checking for jammed pointers or broken crystals. A faulty gauge requires the unit to be depressurized and the gauge replaced.
• Valves and Hoses: Checking for clogs, cracks, or brittle material. Hoses must be unobstructed, and valves must move freely without sticking.
• Safety Features: Ensuring pull pins are not bent or corroded and that tamper seals are intact.

See Table I.1(a) in the NFPA standard for the complete Mechanical Parts Maintenance Checklist, including every component from fill caps and carriage wheels to safety relief devices and pressure regulators.

I.4 Agent and Expelling Means Maintenance

• Contamination: Checking dry chemicals for "caking" or foreign matter.
• Fill Levels: Verifying that agents like water, foam, or wet chemicals are at the correct weight or volume.
• Gas Integrity: For cartridge-operated units, the gas cylinder must be weighed and checked for punctured seals.
• Self-Expelling Agents: For CO₂, weight is the primary indicator of whether the unit is ready for service.

See Table I.1(b) in the NFPA standard for the complete Agent and Expelling Means Maintenance Checklist, detailing specific troubleshooting steps for foam, CO₂, Halon, dry chemical, and wet chemical agents.

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Annex J — Typical Specification of Equipment Capable of Producing Dry Air

J.1 The Compressor Module

To produce high-quality dry air, the standard describes a multistage, air-cooled, and oil-lubricated compressor designed for heavy-duty, continuous use.

• Pressure Rating: The unit is specified to operate at 5,000 psi (34,475 kPa).
• Thermal Management: The design includes intercoolers between each stage of compression and an aftercooler. The goal is to deliver air at a temperature no higher than 20°F (11°C) above the surrounding ambient air.
• Durability: The crankcase is fully enclosed and uses oversized ball bearings and needle bearings for the connecting rods.

J.2 The Dryer System (Moisture Removal)

The dryer system must be capable of stripping moisture and oil vapor from the air before it reaches an extinguisher cylinder. The system uses multiple chambers, starting with a mechanical separator to remove liquid oil and water, followed by replacement cartridges to further refine air quality. The system must deliver air with a dew point of −60°F (−51.1°C) or lower.

J.3 Controls and Instrumentation

• Liquid-filled gauges for monitoring interstage pressure, final discharge pressure, and oil pressure.
• Automatic shutdown sensors for high temperatures or low oil pressure.
• Moisture Monitoring: A continuous moisture monitor is required. If the air's dew point rises above −60°F, a warning light (yellow) is triggered. If not corrected within 1–2 hours, the system performs a hard shutdown (red light) to prevent contaminated air from being used.

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Annex K — Informational References

K.1 The Role of Annex K

This annex is strictly for informational purposes. Publications listed here are not legally part of the NFPA 10 requirements unless also specifically called out in Chapter 2.

K.2 Key NFPA Cross-References

• NFPA 11 & 12: Standards for specialized foam and Carbon Dioxide extinguishing systems.
• NFPA 13, 14 & 15: The "big three" for building water systems (sprinklers, standpipes, and water spray).
• NFPA 72: The National Fire Alarm and Signaling Code.
• NFPA 96: Standard for ventilation and fire protection in commercial kitchens (crucial for Class K compliance).
• NFPA 2001: Requirements for "Clean Agent" systems used for sensitive electronics.

K.3 Industry & Professional References

• ACA (American Coatings Association): Provides the Hazardous Materials Identification System (HMIS) details used on extinguisher labels.
• CGA (Compressed Gas Association): Provides definitive methods for pressure-testing gas cylinders (specifically CGA C-1).
• SFPE (Society of Fire Protection Engineers): References the SFPE Handbook of Fire Protection Engineering for advanced technical analysis.
• UL and ULC (Underwriters Laboratories): Lists the specific fire testing protocols (UL 711 and UL 299) that an extinguisher must pass before receiving its numerical rating.