Class K Fires in Commercial Kitchens: Extinguisher and Suppression Guidance

Commercial kitchen fire overview:  Class K fires involve high-temperature cooking oils and fats, usually in a commercial kitchen. In South Africa, the comparable terminology is commonly Class F. These fires need purpose-selected wet chemical equipment, careful staff procedures and, where the risk warrants it, a fixed kitchen fire suppression system. An ordinary water, foam, CO₂ or ABC dry powder extinguisher should not be treated as an interchangeable solution.

Commercial kitchens combine heat, fuel, electrical equipment, extraction systems and fast-moving staff in a compact workspace. When cooking oil ignites, the fire can intensify quickly and spread through nearby appliances or contaminated ductwork. Facilities teams therefore need more than a label on an extinguisher. They need the right equipment for the hazard, reliable servicing records and a practical response plan.

What is a Class K fire?

Class K is an international fire-class term used mainly for fires involving cooking oils and fats in commercial cooking appliances. South African readers will more commonly encounter Class F for this hazard. Search terminology may differ, but the underlying risk is the same: hot oils and fats can retain enough heat to reignite after visible flames have been suppressed.

Where Class K fires occur

Typical risk areas include deep-fat fryers, tilting pans, griddles, ranges and other appliances that use or accumulate cooking oil. Restaurants, hotels, hospitals, canteens, food factories and institutional kitchens may all have this exposure.

Class K and Class F terminology

Term	Where it is commonly used	Practical meaning
Class K	Common in North American guidance and online searches	Cooking-oil and cooking-fat fires
Class F	Common in South African and other international contexts	Cooking-oil and cooking-fat fires
Wet chemical	Extinguisher or fixed-system agent description	A purpose-selected agent designed for suitable cooking-oil hazards

Facilities and procurement teams should focus on the equipment’s approved application, rating and supplier guidance, rather than choosing by terminology alone.

Why cooking-oil fires behave differently

A grease fire involving vegetable oils or animal fats presents a distinct commercial-kitchen risk. Modern commercial fryers operate at high temperatures and may contain a substantial volume of oil. Once that oil is burning, simply knocking down the flame may not remove enough heat to prevent reignition. A suitable wet chemical agent is intended to cool the burning oil and create a surface layer that helps separate it from oxygen.

This is why adding water is dangerous. Water can sink beneath hot oil, rapidly turn to steam and project burning oil out of the appliance. The result can be a violent spread of flame and severe injury risk.

Which extinguisher is suitable for a Class K or Class F fire?

How a wet chemical Class K fire extinguisher works

A purpose-selected Class K fire extinguisher, commonly described locally as a wet chemical fire extinguisher, is used for commercial cooking-oil and fat hazards. The extinguisher must be appropriate for the specific hazard and correctly positioned, identified and maintained. Its rating, size and location should be determined from the kitchen layout, appliances, oil volumes and risk assessment.

Do not assume that every wet chemical agent is suitable for every appliance or cooking medium. The equipment schedule, manufacturer information and competent fire-protection advice should align.

Why ordinary extinguishers are not interchangeable

• Water: can cause burning oil to spread violently and must not be used on hot cooking oil or a deep fryer fire.
• Foam: should not be treated as a generic substitute for a suitable wet chemical unit.
• CO₂: may provide a temporary flame knockdown in some situations but does not provide the same cooling and surface-sealing action needed for hot cooking oil.
• ABC dry powder: can contaminate the kitchen and may not cool the oil sufficiently to prevent reignition.

A kitchen may need different extinguisher types for different hazards. The unit selected for cooking oil does not automatically replace equipment intended for adjacent electrical, packaging or ordinary combustible risks.

Portable extinguishers and fixed kitchen suppression serve different roles

A portable extinguisher supports an initial response by trained personnel when conditions allow. It is not a substitute for a fixed commercial kitchen fire suppression system where one is required by the risk, equipment arrangement or approved design.

A fixed system can be designed to detect or respond to a fire, discharge agent at protected appliances and extraction points, and interface with relevant shut-off functions. The exact design depends on the listed system, appliance line and site requirements. Changes to fryers, hoods or cooking positions can affect the original coverage and should be reviewed before the kitchen returns to normal operation.

What a kitchen risk review should cover

• Cooking appliances, fuel sources and oil volumes
• Hood, plenum, filter and duct arrangements
• Portable extinguisher types, ratings and locations
• Fixed suppression coverage and service condition
• Emergency isolation and shutdown arrangements
• Escape routes, signage and staff responsibilities
• Cleaning records and grease accumulation
• Changes to equipment or the kitchen layout

The review should consider the kitchen as one operating system. A compliant-looking extinguisher does not compensate for obstructed access, overdue servicing, grease-laden extraction or appliances that no longer sit beneath protected nozzles.

Inspection and servicing priorities

Facilities teams should include portable extinguishers and fixed suppression equipment in a documented inspection and servicing programme. Routine checks can identify missing tamper seals, pressure concerns, blocked access, damaged labels, corrosion, discharged units or overdue service dates.

Fixed systems also need specialist attention to agent containers, pipework, nozzles, detection components, controls and interfaces. Nozzles should remain correctly positioned and protected from grease contamination. Service records should clearly identify the equipment, work completed, defects found and next required action.

ERF Group provides fire extinguisher servicing and support for commercial fire-protection systems, helping facilities teams maintain reliable records and address defects before they become inspection or operational problems.

Cleaning is part of fire-risk control

Grease deposits in filters, hoods and ducts add fuel beyond the appliance itself. A fire that enters contaminated extraction can spread out of sight and become difficult to control. Kitchen cleaning schedules should therefore align with cooking volumes and the actual rate of grease accumulation.

Cleaning must not disturb suppression nozzles, detection components or system controls. If equipment is moved or damaged during cleaning, arrange an inspection before relying on the system.

Staff response must be simple and site-specific

Kitchen staff should understand how to raise the alarm, initiate evacuation, use available isolation controls where this can be done safely, and identify the correct extinguisher. They should also know when not to intervene. Portable firefighting should never delay evacuation or place a person between the fire and their exit.

Training should reflect the actual appliances and equipment on site. Generic instructions copied from overseas sources may use different fire classes, extinguisher markings or operational assumptions.

Procurement questions to ask a fire-protection supplier

Before purchasing or renewing a service agreement, ask the supplier to confirm:

• Which identified hazards each extinguisher or system protects
• Whether the equipment suits the appliances and cooking media
• What inspection and servicing documentation will be provided
• How equipment changes will be assessed
• Who responds to faults, discharges and urgent replacement needs
• Whether multiple sites can be managed consistently

A useful proposal should connect equipment selection to the kitchen risk, rather than offering a generic extinguisher count.

When should the kitchen protection be reassessed?

Arrange a review when appliances are replaced or moved, cooking volumes increase, the menu changes significantly, extraction equipment is altered, a system discharges, or inspection records reveal recurring defects. A reassessment is also sensible when taking over a building with incomplete service records.

What to do after a system discharge

After any fire or discharge, the affected equipment should be professionally inspected, cleaned, reset or replaced as appropriate before normal operation resumes.

How ERF Group supports commercial kitchens

ERF Group supplies and services essential fire equipment for commercial and industrial sites and can help facilities teams coordinate suitable portable extinguishers, kitchen suppression and ongoing maintenance. With more than 50 years of experience, ERF focuses on practical equipment selection, service continuity and clear documentation.

If you are reviewing a restaurant, canteen, hotel or food-production kitchen, Contact us for help assessing the equipment and servicing requirements.