IFSTA Essentials 7: CH 6 Portable Fire Extinguishers

what is a Dry Chemical Extinguisher?

- For class A-B-C fires and or class B-C fires. - most common portable fire extinguishers in use today. - two basic types of dry chem extinguishers 1) regular B-C rated 2) multipurpose ABC rated. - common dry chemicals include: 1) sodium bicarbonate 2) potassium bicarbonate 3) urea potassium bicarbonate 4) potassium chloride 5) monoammonium phosphate -manufacturers mix dry chem agents with additives that make the agents moisture resistant and prevent them from caking. - agent may result in a cloud which may reduce visibility and create respiratory problems but is non toxic. -apply the agent intermittently as needed on any smoldering areas. - many agents can be mildly corrosive to all surfaces. -some dry chems are compatible with foam but others are not --- monoammonium phosphate and some sodium bicarbonate agents will cause the foam blanket to deteriorate when applied in conjunction with or after oam to a Class B fire or spill

what are stored pressure wet chemical extinguishers?

- class K fires -contain a special potassium based low PH agent formulated to operate on the principle of saponification (combines with oils to create a soapy surface.)

What are Carbon Dioxide Extinguishers?

- most effective in extinguishing Class B and Class C fires. - wind will disperse extinguishing agent -they do not require freeze protection - store CO2 under its own pressure as liquefied gas - discharge the agent through a plastic or rubber horn on the end of either a short hose or tube. -gaseous discharge forms dry ice crystals or CO2 "snow" - gas displaces available o2 and smothers the fire . - has very little cooling effect on fire - CO2 does not suppress the surface vapors of fuel and may reignite - wheeled CO2 units have 50-100 pound capacities. - wheeled units are most commonly used in airports and industrial facilities. - must deploy or unwind hose (usually less than 15 feet) from the unit before use.

What are stored pressure water mist extinguishers?

- similar to stored pressure water extinguisher but uses deionized water and nozzles that produce a fine spray instead of a solid stream. - safe to use on class C fires because deionized water because it has no impurities that normal water has -the fine spray enhances cooling and soaking characteristics of water and reduces scattering of the burning materials.

What are clean agent extinguishers

- used in halotron extinguishers. - effectively cool and smother fires in class A and B fuels and inhibit the sustained chemical reaction in class C fuels -agents are nonconductive and can extinguish energized electrical equipment -developed to replace halogen extinguishing agents -halogen was extremely effective in extinguishing fires in computer rooms, aircraft engines, and areas that contain materials that could be easily damaged by water or dry chemical agents. - halogen has damaging effect on atmosphere's ozone layer -halotron is an alternative clean agent that does not harm ozone layer and is EPA approved

What are stored pressure water extinguishers?

-also called air pressurized water (APW) - aka pressurized water extinguishers - useful for all types of small class A fires - useful for extinguishing hot spots during overhaul - store water with compressed air or nitrogen - has a gauge on the valve assembly that displays extinguishers pressure level. - activate the operating valve and the stored pressure forces water up the siphon tube and out through the hose - some manufacturers add class A foam which serves as wetting agent and can aid in extinguishing deep seated fires. it does this by reducing the surface tension of water, allowing water to quickly penetrate the surface

CR #5) What factors should be considered when selecting a portable fire extinguisher?

-classification of the burning fuel - hazards to be protected against - atmospheric conditions - ease of handling the extinguisher - rating -size and intensity of fire - availability of trained personnel to operate the extinguisher - any life hazard or operational concerns

CR# 2) How are portable fire extinguishers rated?

CLASS A -primarily based on amount of water, duration, and range of discharge. - to calculate, multiply "A" by 1 1/4 gallons (5L) CLASS B - numerical ratings 1-B - 640-B -based on approximate square foot area of flammable liquid fire that nonexpert operator can extinguish with one full extinguisher - nonexpert operator is expected to extinguish 1 square foot for each numerical rating. CLASS C - class C just confirms that it will not conduct electricity - used in addition to A/B rating and not on its own. CLASS D - testing considers: reactions of metals and agents, toxicity of fumes produced and products of combustion, time to allow metal to burn completely without fire suppression to the time with extinguisher. - when determined to be safe and effective, a faceplate is placed on extinguisher with instructions. -they do not have a numerical rating. CLASS K - K rating if able to extinguish a fire from a deep fryer using the light oils with surface area of 2.25 square feet minimum

CR #4) What are the three mechanisms used to expel the contents of a portable fire extinguisher

manual pump: physically applies pressure to a pump that increases pressure stored pressure: compressed air or inert gas within the container Pressure cartridge: separate cartridge on the side of the container contains inert gas. cartridge is punctured which forces agent out

CR #6) What are the four steps of the PASS application method for portable fire extinguishers

pull pin aim nozzle squeeze handles together sweep nozzle back and forth

CR #3) What are the four methods that portable fire extinguishers use to extinguish fire?

smothering: excluding oxygen from the burning process cooling: reducing the burning material below its ignition temperature Chemical Flame Inhibition: interrupting the chemical chain reaction in the burning process Saponification: forming an oxygen excluding soapy foam surface

What are pump type water extinguishers?

usually wear them on your back and use a manually operated pump slide. - intended primarily for use on ground cover fires - can be used for small class A fire - nozzle produces straight stream, fog, or water-mist pattern (brush pack HFD)

What are Aqueous film forming foam (AFFF) extinguishers?

-intended for class B fires - useful with fires in suppressing vapors from small liquid fuel spills. -different from stored pressure water extinguishers in two ways. 1) contains a specified amount of AFFF concentrate mixed with water to produce a foam solution 2) has air aspirating foam nozzle that aerates the foam solution. - expelled using compressed air or nitrogen -finished foam creates a vapor seal that extinguishes the flame and prevents reignition - to avoid disturbing the foam blanket do not apply foam directly onto the fuel; instead allow it to rain down gently onto fuel or deflect off nearby surface - most effective on static pools of flammable liquids -not suitable for situations as fuel flowing down from an elevated point or fuel under pressure spraying from a leak

What are dry chemical wheeled units?

-larger versions of handheld - separate storage and pressurized gas - stretch out hose completely to use.

List the common types of portable fire extinguishers

-pump- type water extinguisher -stored pressure -Aqueous film forming foam (AFFF) -CO2 -dry powder -stored pressure water - wet chemical stored pressure -clean agent extinguishers -dry chem extinguishers

CR #1 List and Describe 5 classifications of fire

CLASS A FIRES - ordinary combustibles - fuels such as : textiles, plastics, wood, paper, rubber - all of these fuels can be extinguished by water/ water based agents -dry chemical will also extinguish class A fires. Ratings: -primarily based on amount of water, duration, and range of discharge. - to calculate, multiply "A" by 1 1/4 gallons (5L) CLASS B FIRES- flammable and combustible liquids and gases - fuels such as: alcohol, Gasoline, lubricating oils, liquefied petroleum gas (LPG) - extinguishing agents: carbon dioxide (CO2), dry chemicals, class b foam. Rating: - numerical ratings 1-B - 640-B -based on approximate square foot area of flammable liquid fire that nonexpert operator can extinguish with one full extinguisher - nonexpert operator is expected to extinguish 1 square foot for each numerical rating. CLASS C FIRES- energized electrical equipment - water and water based agents conduct electricity and cannot be used on electrical fires unless power has been shut off - class C just confirms that it will not conduct electricity - used in addition to A/B rating and not on its own. CLASS D FIRES- combustible metals and alloys - Fuels: titanium, magnesium, sodium, lithium, potassium. -identified by bright white emissions - common uses of magnesium: cameras, laptops, luggage, metal box springs for beds, wheels and transmission components for automobiles ** water/ water based agents will cause fire to react violently, emit bits of molten metal, and could injure nearby firefighters. -dry powder extinguishers work best -ONLY use class D extinguisher for class D fire. - testing considers: reactions of metals and agents, toxicity of fumes produced and products of combustion, time to allow metal to burn completely without fire suppression to the time with extinguisher. - when determined to be safe and effective, a faceplate is placed on extinguisher with instructions. -they do not have a numerical rating. CLASS K FIRES- combustible cooking oils such as vegetable or animal fats - wet chemical systems and portable fire extinguishers are used for class K fires - work because of saponification (converts fatty acids or fats in oils to a soapy film including- veggie, canola, peanut, oils with little or no fatty acids - wet chemical agents containing alkaline mixture such as: potassium acetate, potassium carbonate, or potassium citrate, suppress the vapors and smother the fire. - K rating if able to extinguish a fire from a deep fryer using the light oils with surface area of 2.25 square feet minimum

What are the two basic designs for dry chemical extinguishers?

cartridge operated and stored pressure -stored pressure maintains about 200 psi -cartridge operated punctures the cartridge