Portable Fire Extinguisher Ch. 7
NFPA 10 require that portable fire extinguishers be inspected:
At least once a year.
Blue circle label:
Class C
Yellow square label:
Class D
Dry Powder Extinguishers
Class D fires, combustible metals.
Black hexagon label:
Class K
Smothering
Excluding oxygen from the burning process.
Dry Powder
Extinguishing agent suitable for use on combustible metal fires.
Wet Chemical System
Extinguishing system that uses a wet-chemical solution as the primary extinguishing agent; usually installed in range hoods and associated ducting where grease may accumulate.
Dry Chemical
Extinguishing system that uses dry chemical as the primary extinguishing agent; often used to protect areas containing volatile flammable liquids. USED ON CLASS A, B, C FIRES
Air-Aspirating foam nozzle
Foam nozzle especially designed to provide the aeration required to make the highest quality of foam possible; most effective appliance for the generation of low-expansion foam.
Carbon Dioxide (CO2) Extinguishers
Found on both handheld and wheeled units Most effective in extinguishing Class B and Class C fires. Discharge is in the form of a gas so limited reach and gas can be dispersed by wind. Do not require freeze protection. Stored under its own pressure as a liquefied gas ready for release at any time. Agent discharged through plastic for rubber horn. Displaces available oxygen and smothers the fire. Reignition is always a danger due to no vapor suppressing film on the surface.
Aqueous Film Forming Foam (AFFF)
Intended for Class B fires. Surpressing vapors from small liquid fuel spills. Contains a specific amount of AFFF concentrate mixed with water to produce a foam solution *has an air-aspirating foam nozzle that aerates the foam solution, producing a better-quality foam than a standard nozzle provides. Stored using compressed air or nitrogen. Foam floats on the surface of fuels that are lighter than water. The vapor seal created by the film of water extinguishes the flame and prevents reignition. It should be rained down on the fuel or deflected off nearby objects. Most effective on static pools of flammable liquids. Corrossive and can remove paint from tools and apparatus
Chain breaking
Interrupting the chemical chain reaction in the burning process.
Class K fire
Involve combustible cooking oils such as vegetable or animal fats and oils that burn at extremely high temperatures. Extinguish with wet chemical systems.
Class C fire
Involve energized electrical equipment. Water and water based agents CANNOT be used on class C fires UNTIL the electrical energy has been eliminated. Class C extinguishing agents no not conduct electricity making them suitable for electrical fires. Once the power supply has been turned off or disconnected, the fire can be treated as a Class A or B fire.
Class B fire
Involves flammable and combustible liquids and gases, such as alcohol, gasoline, lubricating oils, and liquefied petroleum gas (LPG). Extinguish: carbon dioxide (CO2), dry chemical, and Class B foam.
Class A fire
Involves ordinary combustibles such as textiles, paper, plastics, rubber, and wood. Extinguished easier with: water, water-based agents such as Class A foam or dry chemicals
Class D fire
Involving combustible alloys such as lithium, magnesium, potassium and sodium. Some common magnesium use are in car wheels and transmission components and even some metal box springs in beds. These can be identified by the bright light emissions during the combustion process. The use of water basd agents on Class D fires will cause the fire to react violently, emit bit of molten metal. Extinguish using Class D DRY POWDER extinguisher.
Class C rating
No extinguishing capability tests. Tests are to determine nonconductivity. The tests are to determine electrical nonconductivity.
Class K rating
No numerical rating. Tested to ensure effectiveness against 2.25 square feet of light cooking oil in a deep fat fryer. Class K extinguisher must be capable of saponifying.
Class D rating
No numerical rating. Tests for reactions, toxicity, and metal burn out time. Application instructions are included on the faceplate of the extinguisher, no numerical rating is given.
Cooling
Reducing the burning material below its ignition temperature
NFPA 10
Standard for portable fire extinguishers
Deionized water
Water from which ionic salts, minerals, and impurities have been removed by ion-exchange. Used in water mist extinguisher which can also be used on Class C fires.
Clean agents
have been developed to replace halogenated extinguishing agents. Discharged as a rapidly evaporating liquid that leaves no residue. Clean agents include: FE-36 hexafluoropropane, hydrochlorofluorocarbon (HCCF) hydrofluorocarbon (HFC), perfluorocarbon (PFC) of fluoroidiocarbon (FIC) *These agents effectively cool and smother Class A and B fuels AND are non conductive so they can be used on Class C fires as well
Class A rating
1-A through 40-A 1-A: 1 1/4 gallons 2A: 2 1/2 gallons Rating of water extinguishers is primarily based on the amount of extinguishing agent and the duration and range of the discharge used to extinguish test fires.
Class B rating
1-B through 640-B Based on the approximate square foot area of a flammable liquid fire a non-expert can extinguish. Rating is based on the approximate square foot area of a flammable liquid fire that a nonexpert operator can extinguish using one full extinguisher. The nonexpert operator is expected to extinguish 1 square foot for each numerical rating or value of the extinguisher rating.
Portable fires are identified in two ways:
1. Geometric shapes of specific color with a letter shown within the shape. 2. Pictographs to make the selection of the most appropraite fire extinguisher easier.
When inspecting fire extinguishers, there are 3 factors that determine the value:
1. serviceability 2. Accessibility 3. Simplicity of operation
Saponification
A phenonomenon that occurs when mixtures of alkaline-based chemicals and certain cooking oils come into contact resulting in the formation of a soapy film. Forming and oxygen-excluding soapy foam surface.
Water is stored in a tank along with either compressed:
Air or nitrogen
Corrosive
Capable of causing corrosion by gradually eroding, rusting, or destroying a material
Two basic designs for handheld Dry Chemical extinguishers:
Cartridge operated and stored pressure
Two basic designs for handheld dry chemical extinguishers:
Cartridge operated and stored-pressure. Stored pressure has about 200 psi maintained in tank. Cartridge-operated extinguishers employ a pressure cartridge connected to the agent tank. The agent tank is not pressurized until a plunger is pushed to release the gas from the cartridge. BOTH use either nitrogen or carbon dioxide.
Halogenated extinguishing agents
Chemical compounds that contain carbon plus one or more elements from the halogen series (flurine, chlorine, bromine or iodine). 2 most common used: Halon 1211 and Halon 1301.
Green triangle label:
Class A
Three most common combinations:
Class A-B-C, Class A-B and Class B-C
Red square label:
Class B
Wheeled Dry Chemical units
The same as handheld but bigger. Rated for Class A, B, and C fires.
Wet Chemical stored-pressure extinguisher
Use on Class K fires involving cooking fats, greases, and vegetable and animal oils in commercial kitchens. Contain a special potassium-based, low-pH agent formulated to operate on the principal of saponification in which the agent combines with the oils to create a soapy foam surface over the cooking appliance.
Dry Chemical Extinguishers
Used for Class A-B-C and/or Class B-C fires. *Most common portable fire extinguisher is use today* Two types of Dry Chemical extinguishers: 1. Regular B:C rated 2. Multipurpose and A:B:C Common used dry chemicals: Sodium bicarbonate, Potassium bicarbonate, Urea-potassium bicarbonate, Potassium chloride, Monoammonium phosphate. Nontoxic and safe to use
Water mist
associated with a fire extinguisher capable of atomizing water through a special applicator. Water mist fire extinguishers use distilled water, while backpack pump types use ordinary water.
