Portable Fire Extinguishers: Principles

Slightly modified from a web resource: http://www.fireworld.net/fire_inspection/portable.htm.

Portable Fire Extinguishers Principles

1. Classes of fire
   • (a) Class A - Ordinary combustibles
     1. Wood
     2. Paper
     3. Cloth
     4. Most plastics
     5. Rubber
   • (b) Class B - Flammable and combustible liquids
     1. Petroleum products
     2. Alcohols
   • (c) Class C - Energized electrical equipment
     1. Electric motors
     2. Transformers
     3. Appliances
     4. Electrical distribution panels
   • (d) Class D - Combustible metals
     1. Magnesium
     2. Titanium
     3. Sodium
2. Fire extinguisher rating system
   • (a) Underwriters Laboratories system
     1. All extinguishers are rated according to the class and size of the fire they are designed for.
     2. Class A and B receive a numerical rating to determine the extinguishing potential for each type and size of extinguisher.
     3. 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
     1. 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. 2-A has two times the extinguishing capability of a 1-A, 10-A ten times a 1-A etc.
     3. 1-A to 6-A are rated on the ability to extinguish three types of class A fires.
        • a Wood crib
        • b Wood panel
        • c Excelsior
     4. Ratings above 6-A are subjected to only wood crib tests.
     5. Class B extinguishers are rated 1-B to 640-B. 1-B equals one square foot and is the benchmark.
     6. A 60-B extinguisher should be able to extinguish 60 square feet of flammable liquid fire by a non-expert.
3. (c) Class C extinguishers have no numerical rating, the agents are tested only to determine non- conductivity.
4. (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:
   1. Reactivity
   2. Toxicity
   3. Toxicity of fumes produced
   4. Metal burnout vs. extinguishment.
5. (c) Multiple purpose extinguishers
   1. ABC - Dry chemical
   2. BC - CO2, Dry chemical, Halon
   3. No extinguisher is rated for all four classes.
6. Extinguisher Marking System
   • (a) Letter and Shape
     1. Class A - Triangle
     2. Class B - Square
     3. Class C - Circle
     4. Class D - Yellow star
7. (b) Pictures
   1. Class A - Trash can, campfire
   2. Class B - Gas can
   3. Class C - Outlet and plug
   4. Class D - No standard picture, just the yellow star
8. (c) Pictures and shapes indicate the suitability of the extinguisher as well as the unsuitability. A red line will be drawn through the picture if unsuitable.
9. Types of Portable Fire Extinguishers
   • (a) Class A
     1. Backpack pump tank water extinguisher
     2. Stored pressure water extinguisher
     3. Multi-purpose dry chemical extinguisher
     4. Halon 1211 extinguisher - greater than 9 pounds
   • (b) Class B
     1. Aqueous film forming foam (AFFF)
     2. Halon 1211
     3. Halon 1301
     4. Carbon dioxide (CO2)
     5. Dry chemical
   • (c) Class C
     1. Carbon dioxide
     2. Dry chemical
     3. Halon 1211/1301
   • (d) Class D - dry powders
     1. Lith-x
     2. Met-l-x
     3. Pyrene G-1
10. 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
11. Specific things to inspect
    • (a) Cylinder Condition
      1. Corrosion, cuts, dents, abrasions
      2. Presence of Repairs - welding, brazing
      3. Hanger Attachment - broken or repaired
    • (b) Name Plate or Instruction Guide Plate
      1. Missing
      2. Loose
      3. Illegible wording
    • (c) Hose and Nozzle Assembly
      1. Damaged
      2. Cuts
      3. Aged (brittle), dryrot
    • (d) Nozzle Condition
      1. Cracked
      2. Plugged or clogged
      3. Damaged or bent
    • (e) Head Assembly Condition
      1. Pressure gage - correct pressure, condition
      2. Threads - loose head, damaged
      3. Safety Pin - broken, missing
      4. Tamper indicator (seal) - broken, missing
      5. Handle - operation, condition
    • (f) Agent
      1. Proper level
      2. Condition - caking, age
    • (g) Dates
      1. Last inspection
      2. Hydrostatic test date - last one, next one due
      3. Manufacturers date - obsolete or not