This Presentation Developed By Drew R. Smith This presentation may be modified or reproduced by individual fire departments or training organizations provided.

This Presentation Developed ByDrew R. Smith

This presentation may be modified or reproduced by individual fire departments or training

organizations provided it is not used to generate revenue or in any commercial manner.

The New Class

Class KClass K

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BackgroundIn the past ten

years or so there has been a major change in commercial cooking involving deep-fat fryers and cooking medias

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Fryers

• Older deep-fat fryers were either uninsulated or lightly insulated

• Newer deep-fat fryers are well insulated

Thus, older fryers cool faster than newer fryers

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Cooking media

• Older fryers used animal fat

• Newer fryers use vegetable oil

Vegetable oils cook at higher temperatures than animal fat

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• Unlike gasoline, paint thinner and other flammable liquids, cooking oils have a wide auto-ignition temperature range

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• When cooking oils heat beyond their auto-ignition temperature the oil changes composition resulting in an oil than now has an auto ignition temperature as much as 50°F lower before

ROOM TEMP

HEATED

AI Temp

New AI Temp

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• Unless the entire amount of oil cools below this new auto-ignition temperature the fire will reflash and burn

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A new class of fire is born

NFPA 10 defines Class K as

Fires in cooking appliances that involves combustible

cooking media (vegetable or animal oils or fats)

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Dry Chemical Agents sodium bicarbonate or potassium

bicarbonate, when applied to burning cooking oils create a chemical reaction known as

saponification

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• All cooking oils, greases and fats contain free fatty acids (saturated fat)

• When added to a free fatty acid, alkaline extinguishing agents (such as sodium bicarb or potassium bicarb) form a soap foam on the oil’s surface

• This soap foam performs just like regular firefighting foam to secure vapors and extinguish the fire

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When dry chemical is used to create this saponification it will

not cool all of the oil in the fryer

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Wet chemicals (liquids) that contain an alkaline agent are more effective

• Agents may contain potassium acetate, potassium citrate and/or potassium carbonate

• Applied in a fine mist the agents cool and form the saponification

• These to action cool the oil to below its auto-ignition temperature

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UL tests verify this

• UL conducted dozens of tests comparing Class B-rated dry chemical portable fire extinguishers with these new Class K wet agent portable fire extinguishers

• Tests showed that an 80B (20#) extinguisher that put out a 200-square foot pan fire could not put out a deep-fat fryer with only a 2& sq-foot surface

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• The Dry Chem knocked the fire down (with a big dust cloud) only to reignite

• The Wet Agent fully extinguished the fire for at least 20 minute or until the oil’s temperature was below 60°F

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As a side note...• Wet agents can be found in both

permanent systems and portable fire extinguishers

• They are applied using fine mist nozzles to reduce splashing

• Most permanent kitchen extinguishing systems display a permanent making stating the equipment is UL300-compliant

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• NFPA 10 requires that a portable Class K fire extinguisher only be used AFTER the installed system is activated

• When a Class K portable fire extinguisher is installed in a restaurant there is to be a sign above it stating this requirement

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Class K Fire Extinguishers

• Also carry a class A & B rating

• Class K rating does not carry a number value such as class A & B ratings

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• Wet Agent units are available in both 1&1/2 and 2&1/2 gallon units

• Both the 1&1/2 and 2&1/2 gallon units carry 2-A:1B ratings

While dry-agent Class K extinguishers are available, this program focuses on wet-agent extinguishers

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Fire Department Operations• Recognize the situation and the need for

the Class K fire extinguisher

• Activate the installed system first

• Wearing full protective gear, apply the wet agent from the portable fire extinguisher

• Apply all the agent in the extinguisher EVEN if the fire appears to be out

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REMEMBER

Wet agents works by cooling AND saponification

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References

• “The New Class”, J. Craig Voelkert, NFPA Journal, July/August 1999

• NFPA 10 - Standard for Portable Fire Extinguishers, 1998 Edition

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The End