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Chapter 8 Portable Fire Extinguishers
Introduction • Portable fire extinguishers designed to fight: • Small fires • Unusual fires • Fires that cannot be reached quickly with hoselines • Fire extinguishers are a valuable tool
Introduction (cont’d.) • Four basic PASS steps • P: Pull the pin • A: Aim the nozzle • S: Squeeze the handle • S: Sweep the base of the fire • Fire extinguishers come in a variety of types and sizes
Fire Classification and Risk • Type of material burning defines class of fire • Different classes of fire used to identify type of extinguishers and agents used • Four traditional classes of fire • Additional class added in the past few years • Have a pre-incident plan for fuel types and locations
Class A • Involves ordinary combustibles • Can be extinguished with: • Water • Water-based agents • Foam • Multipurpose dry chemicals • Water usually the agent used
Class B • Flammable and combustible liquids, gases, and greases • Special hazards: situations where fire extinguishers have not been tested • Common extinguishing agents: • Carbon dioxide • Regular and multipurpose dry chemical • Foam
Class C • Involves energized electrical equipment • Water-based agents cannot be used • Turn off electrical power and use appropriate extinguisher • Categorized with another class of extinguisher: BC or ABC • Agents include: • Carbon dioxide • Regular and multipurpose dry chemicals
Class D • Involves combustible metals and alloys • Can have erratic behavior • Water and other agents can react violently when applied to burning combustible metals • Appear to explode when water applied • No universal Class D extinguisher for all metals • Class D agents called dry powders • Not to be confused with dry chemicals
Class K • New classification as of 1998 • Fires in combustible cooking fuels • Agents are usually wet chemicals • Agents usually used in fixed systems
Types of Fire Extinguishers • Many types available • Factors for selecting an extinguisher: • Type and amount of fuel • Person using extinguisher • Type of building construction and occupancy • Type of equipment protected • Main objective is extinguishing the fire
Types of Extinguishing Agents • Water is the basic agent for class A materials • Loaded stream extinguisher • Water-based foam extinguishers have either: • Aqueous Film-Forming Foam (AFFF) • Film-Forming Fluoroprotein Foam (FFFP) • Carbon dioxide: inert gas stored under pressure as a liquid capable of being self-expelled • Dry chemical agents: particles propelled by gaseous medium
Kinds of Extinguishers • Many types are in use today: • Small and handheld • Large and require a wheeled cart • Pump-type extinguishers are hand-pumped devices of two designs • Stored pressure extinguishers expel gas to propel agent • Cartridge-operated extinguishers have expelled gas stored in cartridge on side of container
(A) (B) (C) Figure 8-3 (A) Older versions of fire extinguishers are labeled with colored geometrical shapes with letter designations. (B) Newer fire extinguishers are labeled with a picture label system. (C) Many fire extinguishers can be used to fight more than one type of fire.
Figure 8-6 Inner workings of a stored pressure water extinguisher.
Figure 8-10 Inner workings of a stored pressure dry chemical extinguisher.
Figure 8-14 Inner workings of a carbon dioxide extinguisher with a fixed nozzle.
Rating Systems for Portable Extinguishers • Each class of fuel is subjected to a separate type of extinguisher test for its class • Usually conducted by independent testing agency • Appropriate ratings and symbols are noted on label of extinguisher
Class A • Testing utilizes wood cribbing • Extinguisher should extinguish about 1 cubic foot of wood cribbing • Ratings increase as amount of fire suppressed increases • Class 2-A extinguisher puts out twice the fire of 1-A
Class B • Test involves igniting a pan of flammable liquid, allowing a pre-burn period, and attacking the fire • Size of pan determines rating • 4-square-foot pan yields rating of 4-B • Ratings based on inexperienced extinguisher operator • Larger fires require more agent per area than smaller ones
Class C • Testing tests only the conductivity of: • Agent • Nozzle • Hose • Nozzle combination • No actual fire test • No numbers are assigned with Class C rating
Limitations of Portable Extinguishers • Exceeding capabilities can cause damage and injury • Designed for specific purposes • First-aid method for fire extinguishment • Usually best to pick the larger size • Wrong class extinguisher may not do the job • May cause a reaction or electrical shock
Portable Extinguisher Operation • PASS outlines four simple steps for extinguisher use: • P: Pull the pin • A: Aim the nozzle • S: Squeeze the handle • S: Sweep the base of the fire
Care and Maintenance of Portable Extinguishers • Simple inspections and careful storage prevent most problems • Vehicle operators should periodically move unit from its bracket to hand test weight and do visual check
Care and Maintenance of Portable Extinguishers (cont’d.) • Recharging water extinguisher is a simple process • Performed at fire station by any firefighter • Unscrew and remove the top • Add the manufacturers recommendation of water • Add foam, if required • Replace the top • Charge the extinguisher with the manufacturers recommendation of air
(A) (B) (C) Figure 8-21 (A) Unscrew and remove the top. (B) Add the manufacturer’s recommendation of water. (C) Add foam, if required.
(D) (E) Figure 8-21 (cont’d.) (D) Replace the top. (E) Charge the extinguisher with the manufacturer’s recommendation of air. 8.29
Inspection Requirements • Many popular fire extinguishers of the past are now obsolete • Inspection of fire extinguishers is usually a visual inspection • If something does not look right, extinguisher should be removed and replaced • Extinguishers returned to service should be examined prior to their placement on apparatus
Lessons Learned • Fire extinguishers can be used as: • Initial response tools • To fight fires in special situations • Firefighters classify fires by their fuels • Ordinary combustibles • Flammable liquids and gases • Energized electrical equipment • Four-step process for using an extinguisher: PASS