Portable Fire Extinguishers: Principles
Slightly modified from a web resource:
Portable Fire Extinguishers Principles
- Classes of fire
- (a) Class A - Ordinary combustibles
- Most plastics
- (b) Class B - Flammable and combustible liquids
- Petroleum products
- (c) Class C - Energized electrical equipment
- Electric motors
- Electrical distribution panels
- (d) Class D - Combustible metals
- Fire extinguisher rating system
- (a) Underwriters Laboratories system
- All extinguishers are rated according to the class and size of the
fire they are designed for.
- Class A and B receive a numerical rating to determine the extinguishing
potential for each type and size of extinguisher.
- Class C is basically a class A or B fire with electricity involved.
The C designation indicates a non-conductive agent.
- (b) Class A and B extinguishers
- Class A extinguishers are rated 1-A to 40-A. 1-A equals 1 1/4 gallons
of water and is the benchmark even for non-water type extinguishers.
- 2-A has two times the extinguishing capability of a 1-A, 10-A ten
times a 1-A etc.
- 1-A to 6-A are rated on the ability to extinguish three types of class
- a Wood crib
- b Wood panel
- c Excelsior
- Ratings above 6-A are subjected to only wood crib tests.
- Class B extinguishers are rated 1-B to 640-B. 1-B equals one square
foot and is the benchmark.
- A 60-B extinguisher should be able to extinguish 60 square feet of
flammable liquid fire by a non-expert.
- (c) Class C extinguishers have no numerical rating, the agents are tested
only to determine non- conductivity.
- (d) Class D extinguishers have no numerical rating, however the exact
type of metal the extinguisher is designed for must be on the label. The
agents used, called Dry Powders, are tested for:
- Toxicity of fumes produced
- Metal burnout vs. extinguishment.
- (c) Multiple purpose extinguishers
- ABC - Dry chemical
- BC - CO2, Dry chemical, Halon
- No extinguisher is rated for all four classes.
- Extinguisher Marking System
- (a) Letter and Shape
- Class A - Triangle
- Class B - Square
- Class C - Circle
- Class D - Yellow star
- (b) Pictures
- Class A - Trash can, campfire
- Class B - Gas can
- Class C - Outlet and plug
- Class D - No standard picture, just the yellow star
- (c) Pictures and shapes indicate the suitability of the extinguisher
as well as the unsuitability. A red line will be drawn through the picture
- Types of Portable Fire Extinguishers
- (a) Class A
- Backpack pump tank water extinguisher
- Stored pressure water extinguisher
- Multi-purpose dry chemical extinguisher
- Halon 1211 extinguisher - greater than 9 pounds
- (b) Class B
- Aqueous film forming foam (AFFF)
- Halon 1211
- Halon 1301
- Carbon dioxide (CO2)
- Dry chemical
- (c) Class C
- Carbon dioxide
- Dry chemical
- Halon 1211/1301
- (d) Class D - dry powders
- Pyrene G-1
- General Fire Extinguisher Inspection
- (a) In designated location
- (b) Not actuated, discharged, or tampered with
- (c) No damage
- (d) Conspicuously marked
- (e) Accessible and unobstructed
- Specific things to inspect
- (a) Cylinder Condition
- Corrosion, cuts, dents, abrasions
- Presence of Repairs - welding, brazing
- Hanger Attachment - broken or repaired
- (b) Name Plate or Instruction Guide Plate
- Illegible wording
- (c) Hose and Nozzle Assembly
- Aged (brittle), dryrot
- (d) Nozzle Condition
- Plugged or clogged
- Damaged or bent
- (e) Head Assembly Condition
- Pressure gage - correct pressure, condition
- Threads - loose head, damaged
- Safety Pin - broken, missing
- Tamper indicator (seal) - broken, missing
- Handle - operation, condition
- (f) Agent
- Proper level
- Condition - caking, age
- (g) Dates
- Last inspection
- Hydrostatic test date - last one, next one due
- Manufacturers date - obsolete or not
Lesson plans are provided as a guide for the purpose of training only.
Different rules, requirements and techniques may be applicable in your
Please check all local guidelines and procedures for variances in
application of the above plans.