Chapter 6: Portable Fire extinguishers Flashcards
According to NFPA 1001 it was qualified at the fire fighter one level must know the following about portable fire extinguishers:
o Fire classifications
o Risks associated with each class of fire
o Operating methods of portable fire extinguishers
o Limitations of portable fire extinguishers
The firefighter one must be able to:
o Select appropriate extinguisher size and type
o Safely carry portable fire extinguishers
o Approach fire with portable fire extinguishers
o Operate portable fire extinguishers
how are extinguishers classified
Classified according to type of fire that each is designed to extinguish
how many classes of fire extinguishers are there and what are they
There five class is a portable fire extinguishers to match the five classes of fire: class A,B,C,D, and K
Portable fire extinguishers are identified by
the class letter or combination of letters
The three most common combinations of extinguishers
are class ABC, class BC in class AB
Class a and B extinguishers are classified by
with both letter and numerical rating systems
o for example 4 –A 20 – B:C ,should extinguish a class a fire that is four times larger than a 1– A fire, extinguisher approximately 20 times as much class B fire as a 1 – B extinguisher and extinguish a deep layer of flammable liquid fire of 20 ft.²
The classification a numerical rating system is based on
tests conducted by underwriters laboratories and underwriters laboratories of Canada
One system uses geometric shapes of specific colours with the class letter shown within the shape, the second system uses pictographs
Portable fire extinguisher rating: class A
rating
1-A through 40-A
(A=1 ¼ gallons of water)
- Primarily based on the amount of water and the duration and range of the discharge used in extinguishing test fires
explanations
1-A (1 ¼ gallons (5L) of water)
2-A ( 2 ½ gallons (10L) of water)
3-A (3 ¾ gallons (15L) of water) etc
Portable fire extinguisher rating: class B
1-B through 640-B
Explanations:
Based on the approximate square foot (square meter) Area of a flammable liquid fire a non-expert can extinguish
Portable fire extinguisher rating: class C
ratings
No extinguishing capability tests
Explanations
Tests are to determine non-conductivity
Portable fire extinguisher rating: class D
ratings
No numerical ratings
Explanations
Tested for reactions, toxicity and metal burnout time
Portable fire extinguisher rating: class K
ratings
No numerical ratings
explanations
Test to ensure effectiveness against 2.25 ft.² of light cooking oil in a deep fat fryer
Class a fires:
involve ordinary combustibles such as
o Textiles, plastics, wood, paper, rubber
class A fires can be extinguished with
water based agents like class a foam
- Dry chemicals will also extinguish fires fuelled by class A materials
how to calculate the water capacity of a class
To calculate the water capacity of a class extinguisher multiply the number in front of the A by 1 ¼ gallons (5L) (look at chart above)
Class B fire
involve flammable and combustible liquids and gases
Agents used to extinguish class B fire include
carbon dioxide, dry chemicals and class B foam
Flammable and combustible liquids and gases include:
o Alcohol, lubricating oil’s, gasoline, liquified petroleum gas
o Classified with numerical readings ranging from 1–B through 640-B
o Based on the appropriate square foot area of a flammable liquid fire that are non-expert operator can extinguish using one full extinguisher
o The non-expert operator is expected to extinguish one square foot for each numerical rating or value of the extinguisher rating
Class C fires
involve energized electrical equipment
class c’s are extinguished by
-Class C extinguishing agents will not connect electricity which makes them suitable for electrical fires
-Water and water based agents conduct electrical current and cannot be used on classifiers until the electricity has been shut off
- Power supply has been turned off or disconnected firefighters can treat the fire as a class a or B fire
-Class C rating confirms
that the extinguishing agent will not conduct electricity
-Class D fire
are those involving combustible metals and alloys such as
o Titanium, magnesium, sodium, lithium, potassium
-Magnesium fires can be identified by
the bright white omissions during the combustion process
-Some common uses a magnesium are in:
oCameras, laptops, luggage, metal boxsprings for beds, wheels and transmission components for automobiles
-The use of water or water based agents on class D fires
will cause the fire to react violently, emit bits of molten metal, and could injure nearby firefighters
o Use only class D rated fire extinguishers to extinguish metal fires
class d fires can be extinguished by
-Class D dry powder extinguishers
-Do not confused dry powder extinguishers with dry chemical units used on class A, B, and C fires
Class K fires
involve combustible cooking oils such as vegetable or animal fats and oil that burn at extremely high temperatures
what is used to extinguish class k fires
-Wet chemicals systems and portable fire extinguishers are used to control and extinguish Class K fires
how do class K fire extinguishers work
saponification
Wet chemical agents containing an alkaline mixture, such as potassium acetate, potassium carbonate, or potassium citrate, supress the vapors and smother the fire
Saponification:
converts the fatty acids or fats in the following oils to a soapy film:
o Vegetable oils
o Canola oils
o Peanut oils
o Other oils with little or no fatty acids
-Portable fire extinguishers are also rated according to
the type of extinguishing agent and the mechanism used to expel the contents
Smothering
excluding oxygen from the burning process
Smothering extinguishing agents will not work on material that contain their own oxidizing agents
Cooling
reducing the burning material below its ignition temperature
Chemical flame inhibition
interrupting the chemical chain reaction in the burning process
extinguishing techniques
smothering
cooling
chemical flame inhibition
saponification
Water type extinguishers must be protected against freezing if exposed the temperature is lower than _________ protection options include adding antifreeze to the water or storing them in warm areas
40F or 4 Celsius
Extinguishing agent characteristics: water
Primary method
Cooling
secondary method
Oxygen depletion