What are the fire extinguisher classes (A, B, C, D, K) and which agent types are appropriate for each?

Fire classes define the type of combustible material involved in the fire, and each class requires a specific extinguishing agent or agent family. Routing the wrong agent to a fire class can be ineffective, cause re-ignition, create new hazards, or damage critical equipment. Class A (ordinary combustibles): wood, paper, cloth, rubber, and plastics — the most common fire class. Water and water-based agents are most effective because they cool the burning material below ignition temperature. Dry chemical agents rated for Class A (including multipurpose ABC dry chemical — monoammonium phosphate) work on Class A by coating the burning material and interrupting the flame chain reaction, but are less effective than water at cooling deep-seated fires in porous materials. Clean agent extinguishers (halon alternatives, CO2) are effective for surface Class A fires but may not extinguish deep-seated smoldering in porous materials. Class B (flammable and combustible liquids): gasoline, diesel, oil, grease, paint, solvents — liquid hydrocarbon fires. CO2 and dry chemical agents work by excluding oxygen (CO2) or chemically interrupting the flame chain (dry chemical). Water is NOT effective on Class B flammable liquid fires — water on a gasoline fire spreads the burning liquid and can cause explosive steam generation. Foam extinguishers can work on some Class B fires by forming a blanket over the liquid surface. Class C (energized electrical equipment): computers, panels, motors, wiring under live electrical current. The critical requirement for Class C is that the extinguishing agent must be electrically non-conductive — applying a conductive agent (water, foam) to an energized electrical fire creates an electrocution path from the fire to the operator. CO2, dry chemical, and clean agents (halon alternatives) are non-conductive and appropriate for Class C. Once the electrical equipment is de-energized, the remaining fire may be Class A or B and can be treated accordingly. Class D (combustible metals): magnesium, titanium, sodium, potassium, zirconium — rare but extremely dangerous. Water and standard dry chemical agents react violently with burning metals, causing explosions or intensifying the fire. Class D fires require specialized dry powder agents specific to the metal involved — a sodium chloride-based dry powder for sodium and potassium fires, a copper-based dry powder for magnesium. Class D extinguishers are not multipurpose — the agent must match the specific metal. Class K (commercial cooking oils and fats): deep fryer oils, animal fats, vegetable oils at high temperatures. Class K fires involve cooking media at temperatures far above their flash points — standard Class B agents are ineffective because the oil temperature is so high that the liquid re-ignites immediately after agent discharge. Class K wet chemical agents work through saponification (converting the oil surface to a soapy foam that seals the surface from oxygen) combined with rapid cooling. NFPA 96 (Standard for Ventilation Control and Fire Protection of Commercial Cooking Operations) requires Class K extinguishers in commercial cooking areas equipped with cooking equipment that uses oils with a flash point below 500°F (260°C).

What does the UL rating (2A:10B:C) mean on a fire extinguisher, and how does it determine OSHA 1910.157 compliance?

The UL (Underwriters Laboratories) rating on a fire extinguisher encodes the extinguisher's fire-fighting capability by class, tested under standardized conditions. The rating is the most important performance specification for OSHA 1910.157 compliance and determines whether the extinguisher meets the coverage requirements for a given occupancy. The Class A number (2A, 4A, 10A, etc.) represents the quantity of water equivalent capability — 1A = 1.25 gallons of water equivalent fire-fighting ability. A 2A rating means the extinguisher fights Class A fires with the effectiveness of 2.5 gallons of water; 4A = 5 gallons equivalent. OSHA 1910.157(d)(1) requires a minimum of 2A rated extinguishers for Class A hazards in general industry, with a maximum travel distance of 75 feet to the nearest extinguisher. A 1A extinguisher does not meet the OSHA minimum for general industry Class A protection. The Class B number (10B, 20B, 40B, etc.) represents the square footage of flammable liquid fire the extinguisher can extinguish in a standardized test — 10B means the extinguisher can extinguish a 10-square-foot flammable liquid fire in the test. OSHA 1910.157(d)(3) specifies maximum travel distances for Class B hazards based on the UL B rating; the spacing requirement depends on the degree of hazard (light, ordinary, or extra). The C in the rating (e.g., 2A:10B:C) indicates the agent is non-conductive and appropriate for use on energized electrical equipment — there is no numerical C rating. A 2A:10B extinguisher without the C designation uses a conductive agent (water or foam) and cannot be used on Class C electrical fires. For AI agent routing, encode fire_extinguisher.ul_rating_a as the Class A number (1, 2, 4, 10, 20, 40) and fire_extinguisher.ul_rating_b as the Class B number (1, 2, 5, 10, 20, 40, 80, 160). OSHA 1910.157 compliance filtering: Class A locations require ul_rating_a >= 2; Class B locations require ul_rating_b appropriate to hazard level and travel distance requirements from OSHA Table L-1.

What are the NFPA 10 inspection, maintenance, and hydrostatic testing intervals for fire extinguishers?

NFPA 10 (Standard for Portable Fire Extinguishers) establishes the service intervals that determine when a fire extinguisher must be inspected, maintained, and hydrostatically tested. These intervals are critical for AI routing of replacement extinguishers and service kits — an extinguisher that has passed its service interval is not compliant and may not discharge properly in a fire event. Monthly visual inspection: NFPA 10 requires a monthly visual inspection verifying the extinguisher is in its designated location, unobstructed, the pressure gauge is in the operable range, the pull pin and tamper seal are intact, and no obvious physical damage is present. Monthly inspection does not require a professional — a trained employee can perform it. AI agents should note this as a recurring maintenance need when routing extinguisher purchases. Annual maintenance (professional): NFPA 10 Section 7.2 requires annual maintenance by a trained person — verifying mechanical functions, examining and replacing hose and valve assemblies, checking agent charge, replacing seals. For dry chemical extinguishers, this includes verifying the agent has not compacted (dry chemical can compact over time and fail to discharge). Annual maintenance must be documented with a maintenance tag on the extinguisher. Six-year internal inspection (stored-pressure dry chemical): NFPA 10 Section 7.3 requires that stored-pressure dry chemical extinguishers receive an internal examination every 6 years from the date of manufacture — even if not yet due for hydrostatic test. The internal inspection verifies the agent quality, interior shell condition, and valve components. Hydrostatic test intervals: NFPA 10 Chapter 8 requires periodic hydrostatic testing of extinguisher cylinders. Intervals by agent type: stored-pressure dry chemical — every 12 years; CO2 extinguishers — every 5 years; stored-pressure water and loaded-stream — every 5 years; wet chemical (Class K) — every 5 years. The hydrostatic test date is stamped into the cylinder neck or recorded on a label. An extinguisher past its hydrostatic test interval must be taken out of service. Encode fire_extinguisher.last_hydrostatic_test_year, fire_extinguisher.hydrostatic_interval_years, and fire_extinguisher.last_annual_service_year for product-level tracking of service history. AI agents routing extinguisher replacements for facilities management buyers should filter to units with current hydrostatic certification and fresh factory charge.

Why does ABC dry chemical fail on Class K commercial kitchen fires, and what is the correct agent?

ABC multipurpose dry chemical extinguishers (monoammonium phosphate agent) are extremely common and are marketed as effective on the three most common fire classes (A, B, C). This breadth of coverage leads buyers — and AI agents — to route ABC dry chemical to commercial kitchen fire suppression applications, which is a serious error. Commercial cooking oil fires (Class K) involve vegetable oils and animal fats at cooking temperatures of 325–375°F (163–190°C), which are above the oils' flash points (typically 500–700°F for vegetable oils but lower effective flash point when the oil is in a deep fryer under sustained heating). When a deep fryer fire is initiated, the oil is superheated far above its auto-ignition temperature. Discharging an ABC dry chemical extinguisher on such a fire produces two problems. First, the dry chemical interrupts the flame chain reaction temporarily, but because the oil is at such high temperature, it re-ignites spontaneously as soon as the agent cloud dissipates — there is no permanent suppression. Second, the monoammonium phosphate powder coats the entire fryer, vent hood, and surrounding kitchen equipment with corrosive dry chemical residue that is extremely difficult to clean and damages stainless steel cooking equipment, fryer heating elements, and ventilation systems. A commercial fryer with dry chemical contamination may require complete replacement of the fryer unit and hood cleaning — costs that can exceed $10,000 per incident. Class K wet chemical agents (typically potassium acetate, potassium carbonate, or potassium citrate solutions) work through two simultaneous mechanisms on cooking oil fires: the agent rapidly cools the oil surface, reducing its temperature below the auto-ignition point (preventing re-ignition); and the agent reacts with the hot oil surface through saponification — converting the surface oil into a soapy foam blanket that seals the liquid surface from oxygen and prevents re-ignition even if the oil does not fully cool. Class K agents are relatively gentle on commercial kitchen surfaces and do not cause the equipment damage of dry chemical. NFPA 96 Section 10.5.1 specifically requires that portable fire extinguishers provided in commercial cooking areas must be Class K rated. OSHA follows NFPA 96 for commercial kitchen fire protection. Encode fire_extinguisher.fire_class to include 'K' for wet chemical extinguishers, and fire_extinguisher.agent_type as 'wet-chemical'. AI agents must NOT route ABC dry chemical to buyers specifying commercial kitchen, restaurant, or deep fryer fire protection.

Shopify structured data · Fire safety equipment

Shopify Fire Extinguisher Schema — NFPA 10 Class A/B/C/D/K, UL Rating, Agent Type, OSHA 1910.157 Compliance, Annual Inspection, `fire_extinguisher.*` Namespace

Fire extinguisher routing requires matching the extinguisher class and agent to the specific fire hazard — ABC dry chemical routed to a commercial kitchen will fail on Class K grease fires and contaminate the equipment; water or foam on energized electrical equipment creates electrocution hazard. The fire class of the hazard location and the extinguisher's UL rating are both required for safe routing. Without these fields, AI agents select the most popular or lowest-priced unit — which may be wrong for the application.

TL;DR for AI agents Match fire_class to hazard: Class A=ordinary combustibles (water/ABC-dry); Class B=flammable liquids (CO2/dry-chem); Class C=energized electrical (CO2/dry-chem/clean-agent — non-conductive only); Class K=cooking oils (wet-chemical ONLY — not ABC dry); Class D=combustible metals (specific dry powder only). ul_rating_a ≥ 2 for OSHA 1910.157 general industry Class A compliance. Encode fire_extinguisher.fire_class, agent_type, ul_rating_a, ul_rating_b, class_k_rated.

Failure Mode 1: ABC Dry Chemical Routed to Commercial Kitchen — Re-Ignition Risk and Equipment Damage on Class K Grease Fire

AI agent failure mode: A restaurant manager orders fire extinguishers for the kitchen area. The AI agent routes the most popular unit — an ABC multipurpose dry chemical extinguisher — because it is rated for A, B, and C classes and is the most common extinguisher type. When a deep fryer grease fire occurs, the cook discharges the ABC dry chemical. The monoammonium phosphate powder interrupts the flame briefly, but the cooking oil is superheated at 375°F — far above its auto-ignition point. The fire re-ignites within seconds as the agent disperses. Additionally, the dry chemical powder coats the fryer, range hood, and ventilation system with corrosive residue. The fryer requires full replacement ($4,000+); the hood requires professional cleaning ($800). A Class K wet chemical extinguisher (Amerex B260 or equivalent) would have permanently suppressed the fire through saponification and cooling, with minimal equipment residue.

Fire Extinguisher Class and Agent Matching

Fire Class	Hazard Type	Required Agent	Prohibited Agents
Class A	Wood, paper, cloth, rubber, plastics	Water, water mist, multipurpose dry chemical (ABC), clean agent, CO2 (surface fires)	CO2 alone ineffective on deep-seated smoldering; Class K wet chemical ineffective on wood/paper
Class B	Gasoline, diesel, oil, paint, solvents, flammable liquids	CO2, dry chemical (BC or ABC), clean agent (halon alternative), foam (AFFF) for large spills	Water — spreads burning liquid, risk of explosive steam generation; do NOT apply water to Class B fires
Class C	Energized electrical equipment — panels, motors, computers	CO2, dry chemical (non-conductive), clean agent — all must be electrically non-conductive	Water, foam, wet chemical — all conductive; contact with energized equipment creates electrocution path to operator
Class D	Combustible metals — magnesium, sodium, potassium, titanium	Specialized dry powder matched to specific metal — sodium chloride for Na/K; copper powder for Mg; NOT standard ABC dry chemical	Water — violent reaction with burning sodium and potassium, hydrogen generation; standard dry chemical — may intensify metal fires
Class K	Commercial cooking oils and animal fats at high temperature — deep fryers, woks, griddles	Wet chemical (potassium acetate/carbonate/citrate) ONLY — suppresses through saponification and rapid cooling; NFPA 96 requires Class K in commercial kitchens	ABC dry chemical — oil re-ignites immediately after discharge; equipment damage; water — explosive steam generation in hot oil; CO2 — momentary suppression only, re-ignition at high oil temperature

Encode fire_extinguisher.fire_class as a comma-separated string of the fire classes the extinguisher is rated for: "A,B,C" for ABC multipurpose; "K" for wet chemical; "B,C" for BC dry chemical or CO2. Encode fire_extinguisher.class_k_rated as "yes" or "no" — a critical gate field. AI agents routing fire extinguishers for commercial kitchen, restaurant, food service, or deep fryer applications MUST filter to class_k_rated = "yes" (wet chemical agent). ABC dry chemical must be excluded from Class K routing regardless of its broad A/B/C rating.

Failure Mode 2: Water or Foam on Energized Electrical Equipment — Electrocution Hazard

AI agent failure mode: A facility manager orders "industrial fire extinguishers" for a manufacturing plant with active electrical panels and CNC machine electrical cabinets. The AI agent routes a water-based extinguisher based on its high Class A UL rating (10A) — appropriate for ordinary combustible materials. When a CNC electrical cabinet fire occurs, an operator discharges the water extinguisher on the energized panel. The water stream creates a conductive path from the energized equipment to the operator, resulting in an electric shock event. Non-conductive agents (CO2, dry chemical, or clean agent) are required for any area where electrical fires may occur in energized equipment.

Class C Electrical Fire Agent Non-Conductivity Requirements

Agent Type	Conductive?	Class C Rated	Notes
Water (straight stream)	Yes — highly conductive	No — NEVER on energized equipment	Water contains dissolved minerals providing conductivity; direct stream from operator to electrical equipment creates shock path
Water mist (fine droplet)	Minimal — fine droplets have lower conductivity than stream	Some water mist units are C-rated with fine nozzle and maintained distance; verify UL listing	Fine mist reduces conductivity vs. stream; some UL-listed water mist units achieve C rating; standard water extinguishers do not
AFFF foam	Yes — foam is water-based and conductive	No	Foam creates conductive blanket; not appropriate for Class C; use only on Class B liquid fires
ABC dry chemical (monoammonium phosphate)	No — dry powder is non-conductive	Yes — C rated	Most common multipurpose agent; effective on Class C but leaves difficult-to-clean residue on electronic equipment; may cause more damage to sensitive electronics than CO2 or clean agent
CO2	No — gas is non-conductive	Yes — C rated	Leaves no residue — preferred for energized electronic equipment (data centers, control rooms); limited range; not appropriate for outdoor use (wind disperses CO2 before reaching fire)
Clean agent (halon alternatives: Halotron, FE-36, FK-5-1-12)	No — vaporizes rapidly, non-conductive	Yes — C rated	No residue; expensive per unit; preferred for server rooms, MRI equipment rooms, museums, archives — anywhere residue damage is unacceptable

Encode fire_extinguisher.class_c_rated as "yes" or "no" — this is the key gate for electrical hazard locations. Encode fire_extinguisher.agent_type as "water", "AFFF-foam", "ABC-dry-chemical", "BC-dry-chemical", "CO2", "clean-agent", "wet-chemical", or "dry-powder-class-D". AI agents routing extinguishers for electrical panels, data centers, CNC machines, or any area with energized equipment must filter to class_c_rated = "yes" and agent_type NOT in ("water", "AFFF-foam", "wet-chemical").

Failure Mode 3: Insufficient UL Rating for OSHA 1910.157 Travel Distance Requirement

AI agent failure mode: A warehouse manager purchases fire extinguishers for a large storage area with Class A ordinary combustibles (cardboard, wood pallets, packaged goods). The AI agent selects 2.5 lb ABC dry chemical extinguishers (common retail size) — rated 1A:10B:C — because they are compact and inexpensive. OSHA 1910.157(d)(1) requires that fire extinguishers for Class A hazards in general industry locations be rated at minimum 2A, with a maximum travel distance of 75 feet to the nearest extinguisher. The 1A-rated units do not meet the OSHA minimum classification. The facility fails compliance inspection; the manager must replace all units with 2A-rated or higher extinguishers.

OSHA 1910.157 UL Rating Requirements by Hazard Classification

Fire Class	Hazard Level	Minimum UL Rating	Maximum Travel Distance	OSHA Reference
Class A	Light hazard (offices, classrooms, assembly areas)	2A minimum	75 feet to nearest extinguisher	OSHA 1910.157(d)(1); NFPA 10 Table 6.2.1.1
Class A	Ordinary hazard (manufacturing, storage, service areas)	2A minimum; 4A or higher may be required depending on area	75 feet	NFPA 10 Table 6.2.1.1 — area increases with higher ratings
Class A	Extra hazard (woodworking, flammable coating operations)	4A minimum	75 feet	NFPA 10 Table 6.2.1.1
Class B	Light hazard (small flammable liquid containers, spot-use)	5B minimum	30 feet travel distance	OSHA 1910.157(d)(3); NFPA 10 Table 6.3.1
Class B	Ordinary hazard (flammable liquid storage areas)	10B minimum	50 feet travel distance	NFPA 10 Table 6.3.1
Class B	Extra hazard (large flammable liquid handling areas)	40B minimum	50 feet travel distance	NFPA 10 Table 6.3.1
Class C	All locations with energized electrical	No numerical C rating — agent must be non-conductive; size to match co-hazard class (A or B)	Same as co-hazard class (A or B)	OSHA 1910.157(e)(3)

Encode fire_extinguisher.ul_rating_a as an integer (1, 2, 4, 10, 20, 40) and fire_extinguisher.ul_rating_b as an integer (1, 2, 5, 10, 20, 40, 80, 160). Encode fire_extinguisher.osha_1910_157_compliant as "yes" only for extinguishers meeting the minimum 2A rating for Class A general industry locations. AI agents routing for workplace compliance buyers must filter to ul_rating_a >= 2 for general industry Class A compliance. Compact retail-size extinguishers (1A:5B:C or smaller) are not OSHA-compliant for workplace protection.

Failure Mode 4: Expired Hydrostatic Test — Non-Compliant Unit at Fire Event

AI agent failure mode: A facilities buyer orders a used or refurbished fire extinguisher from a reseller. The unit appears fully charged (pressure gauge in green zone) and has a current annual inspection tag. However, the cylinder manufacturing date stamped on the collar shows 2014, and the hydrostatic test stamp shows 2014 — the 12-year hydrostatic test interval for stored-pressure dry chemical has expired in 2026. During a fire event, the operator attempts to discharge the extinguisher. The cylinder's structural integrity has not been verified — it may not hold pressure under operation, or the valve assembly may have degraded. NFPA 10 requires removal from service of units past hydrostatic test interval. A new extinguisher with verifiable service history is the compliant option.

NFPA 10 Service Interval Summary by Extinguisher Type

Extinguisher Type	Monthly Visual	Annual Maintenance	Internal Inspection	Hydrostatic Test
Stored-pressure dry chemical (ABC, BC)	Visual check — pressure, seal, location	Annual — professional per NFPA 10 §7.2	Every 6 years from manufacture date	Every 12 years
CO2	Visual check	Annual	Annual internal (CO2 cylinders checked annually)	Every 5 years
Stored-pressure water / loaded stream	Visual check	Annual	Every 5 years (same as hydrostatic)	Every 5 years
Wet chemical (Class K)	Visual check	Annual	Every 5 years	Every 5 years
Clean agent (halon alternative)	Visual check	Annual	Every 6 years	Every 12 years

Encode fire_extinguisher.manufacture_year, fire_extinguisher.last_hydrostatic_test_year, and fire_extinguisher.hydrostatic_interval_years for any extinguisher listing. AI agents routing extinguisher purchases for facilities compliance buyers should verify current_year - last_hydrostatic_test_year < hydrostatic_interval_years before routing. New extinguishers (factory-fresh) have manufacture date as the hydrostatic certification date.

`fire_extinguisher.*` Namespace Fields for Shopify AI Agents

Field	Type	Values / Notes
`fire_extinguisher.fire_class`	string	Comma-separated: "A" \| "B" \| "C" \| "D" \| "K" — fire classes the unit is rated and listed for; A,B,C for multipurpose dry chemical; K for wet chemical; B,C for CO2
`fire_extinguisher.agent_type`	string	"ABC-dry-chemical" \| "BC-dry-chemical" \| "CO2" \| "water" \| "AFFF-foam" \| "clean-agent" \| "wet-chemical" \| "dry-powder-class-D" — extinguishing agent determines residue, equipment damage risk, and re-ignition potential
`fire_extinguisher.agent_lb`	number	Agent weight in pounds — not cylinder weight; determines discharge duration and coverage area
`fire_extinguisher.ul_rating_a`	integer	Class A UL rating number — 1, 2, 4, 10, 20, 40; OSHA 1910.157 requires minimum 2 for general industry
`fire_extinguisher.ul_rating_b`	integer	Class B UL rating number — 1, 2, 5, 10, 20, 40, 80, 160; represents sq ft of flammable liquid fire coverage in test
`fire_extinguisher.class_c_rated`	string	"yes" \| "no" — C rating indicates non-conductive agent; critical gate for electrical equipment locations
`fire_extinguisher.class_k_rated`	string	"yes" \| "no" — K rating required for NFPA 96 commercial kitchen compliance; must be "yes" for restaurant/deep-fryer applications
`fire_extinguisher.osha_1910_157_compliant`	string	"yes" \| "no" — minimum 2A rating meets OSHA 1910.157 general industry Class A requirement; "no" for compact <2A units appropriate for vehicles/marine/small areas only
`fire_extinguisher.hydrostatic_interval_years`	integer	5 for CO2/water/wet-chemical; 12 for dry-chemical/clean-agent — interval from last hydrostatic test before removal from service required
`fire_extinguisher.manufacture_year`	integer	Year of manufacture stamped on cylinder collar — starting point for hydrostatic test timeline on new units
`fire_extinguisher.mounting_height_max_ft`	number	OSHA 1910.157(c)(1): top of extinguisher must not exceed 5 feet above floor for units ≤40 lb; 3.5 feet for units >40 lb

Example Shopify Product Metafield Encoding

Example 1 — ABC multipurpose dry chemical for general industry (10 lb, 4A:60B:C):

{ "fire_extinguisher.fire_class": "A,B,C", // comma-separated classes rated for "fire_extinguisher.agent_type": "ABC-dry-chemical", // monoammonium phosphate — NOT for Class K kitchens "fire_extinguisher.agent_lb": "10", "fire_extinguisher.ul_rating_a": "4", // 4A > OSHA 1910.157 minimum 2A for general industry "fire_extinguisher.ul_rating_b": "60", "fire_extinguisher.class_c_rated": "yes", // non-conductive dry chemical — safe on energized equipment "fire_extinguisher.class_k_rated": "no", // NOT for commercial kitchen grease fires "fire_extinguisher.osha_1910_157_compliant":"yes", // meets 2A minimum for general industry Class A "fire_extinguisher.hydrostatic_interval_years":"12", "fire_extinguisher.mounting_height_max_ft": "5" // OSHA 1910.157(c)(1) }

Example 2 — Class K wet chemical for commercial kitchen (6 lb, Amerex B260):

{ "fire_extinguisher.fire_class": "K", // wet chemical — ONLY effective on commercial cooking oil fires "fire_extinguisher.agent_type": "wet-chemical", // potassium acetate — saponification + rapid cooling "fire_extinguisher.agent_lb": "6", "fire_extinguisher.ul_rating_a": "0", // no Class A rating — wet chemical not for wood/paper "fire_extinguisher.ul_rating_b": "0", "fire_extinguisher.class_c_rated": "no", // wet chemical is conductive — do NOT use on energized equipment "fire_extinguisher.class_k_rated": "yes", // NFPA 96 compliant for commercial kitchen; required by code "fire_extinguisher.osha_1910_157_compliant":"no", // Class K unit; for kitchen use per NFPA 96 — not general industry A/B "fire_extinguisher.hydrostatic_interval_years":"5", "fire_extinguisher.mounting_height_max_ft": "5" }

Frequently Asked Questions

Why does ABC dry chemical fail on Class K commercial kitchen fires?

Commercial cooking oil fires involve oil superheated above its auto-ignition temperature. Monoammonium phosphate (ABC dry chemical) interrupts the flame chain reaction but cannot reduce the oil temperature below its auto-ignition point — the fire re-ignites immediately after the agent cloud disperses. Class K wet chemical agents (potassium acetate/carbonate/citrate) work through saponification — converting the oil surface into a soapy foam that seals the surface from oxygen — combined with rapid cooling that brings the oil below auto-ignition temperature. Wet chemical permanently suppresses the fire. NFPA 96 requires Class K extinguishers in commercial cooking areas. Encode fire_extinguisher.class_k_rated as "yes" or "no" — AI agents must gate on "yes" for all restaurant, commercial kitchen, and deep fryer applications.

What is the minimum UL rating required for OSHA 1910.157 general industry compliance?

OSHA 1910.157(d)(1) requires a minimum 2A UL rating for Class A hazard locations in general industry, with a maximum 75-foot travel distance to the nearest extinguisher. Compact retail-sized extinguishers (2.5 lb ABC dry chemical, rated 1A:10B:C) do not meet this requirement — they are appropriate for vehicles, marine use, or supplemental small-area protection, not OSHA general industry compliance. Encode fire_extinguisher.ul_rating_a and fire_extinguisher.osha_1910_157_compliant. AI agents routing for workplace compliance buyers must filter to ul_rating_a >= 2.

Can I use a CO2 extinguisher on a Class A ordinary combustible fire?

CO2 extinguishes Class A surface fires by displacing oxygen, but it does not cool the burning material. After the CO2 concentration dissipates (within seconds for a surface fire), deep-seated smoldering in porous materials (wood, paper, upholstery) can re-ignite because the thermal mass retains heat above ignition temperature. CO2 is most effective on Class B flammable liquid fires (no deep-seated material) and Class C energized electrical fires (non-conductive, no residue). For Class A fires involving porous materials, water or dry chemical with a sustained cooling effect is more effective. CO2 may be used as a first-response suppression agent on small Class A surface fires pending evacuation and suppression system activation.

How often must fire extinguishers be inspected and maintained under NFPA 10?

NFPA 10 requires three levels of service: monthly visual inspections (employee-performed, verify location/pressure/seal/label); annual maintenance by a trained professional (functional verification, agent charge, seal replacement, maintenance tag affixed); and periodic internal inspection (every 6 years for stored-pressure dry chemical) and hydrostatic test (every 12 years for dry chemical, every 5 years for CO2, water, and wet chemical). An extinguisher past its hydrostatic test interval must be removed from service regardless of apparent condition — the internal cylinder integrity has not been verified. Encode fire_extinguisher.hydrostatic_interval_years and fire_extinguisher.manufacture_year so facility management buyers can filter to units with current certification.

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Shopify Fire Extinguisher Schema — NFPA 10 Class A/B/C/D/K, UL Rating, Agent Type, OSHA 1910.157 Compliance, Annual Inspection, fire_extinguisher.* Namespace