Home Podcasts THMG094 – Extinguishing Agents, Part II

THMG094 – Extinguishing Agents, Part II


In part two of this three-part series, Bob and Mike continue their exploration of extinguishing agents.

Complete Show Notes

2:00 Purple K Extinguishers

  • The periodic symbol for potassium is K, and the color of the extinguisher is purple

2:45 Water

2:50 F-500 Extinguishers

3:05 CO2

  • Clean, gaseous agent that displaces oxygen (3-atom molecule made of carbon, oxygen, and oxygen)
  • Not intended for Class A fires, as the high-pressure cloud of gas can scatter burning materials
  • CO2 also isn’t suitable for use on fires containing their own oxygen source or metals and cooking media (Class K)
  • While it can be suitable for people who are on fire, try to avoid using it – can cause frostbite and suffocation

6:50 Foams

  • High-expansion foams
    • Effective for use during liquid natural gas events
    • Contra-indicated for Class B liquid fuels
  • AR-AFFF (alcohol-resistant aqueous film-forming foams)
    • Used on fuel fires containing alcohol
    • Forms a membrane between the fuel and the foam, preventing the alcohol from breaking down the foam blanket
  • AFFF (aqueous film-forming foam concentrates)
    • Used on A and B-type fires for vapor suppression
    • The most common type of portable foam extinguisher
    • Developed in the 1960s under Project Light Water, a joint venture between 3M and the U.S. Navy
    • Forms a film that floats out before the foam blanket, sealing the surface and smothering the fire by excluding oxygen
    • Widely used for ARFF firefighting at airports
    • Discharged through an air-aspirating branchpipe nozzle or a spray nozzle
  • FFFP (film-forming fluoroprotein)
    • Contains naturally occurring proteins from animal by-products and synthetic film-forming agents to create a heat blanket that’s more heat resistant than strictly synthetic AFFF foams
    • Works well on alcohol-based liquids and is used widely in motorsports
    • Not appropriate for use on ethanol over 10%
  • CAFS (compressed air foam system)
    • Different from a standard stored-pressure pre-mix foam extinguisher because it operates at a higher pressure (140 psi)
    • Aerates the foam with an attached compressed gas cylinder, instead of an air-aspirating nozzle
    • Generally used on Class A fires and with very dry foam on Class B for vapor suppression
    • Very expensive, special-purpose extinguishers typically used by fire departments or other safety professionals

17:45 MIL-F-24385

  • Type of AFFF made specifically for airport firefighting
  • Currently used by all FAA regulated crash fire rescue vehicles and the military

18:50 Halon

  • Gaseous agents that inhibit the chemical reaction of the fire (includes Halon 1211 and Halon 1301
  • Banned from new production under the Montreal Protocol as of January 1, 1994 because its properties contribute to ozone depletion and it has a long atmospheric lifetime (usually 400 years)
  • The rest of the industry has moved to halon alternatives, but Halon 1211 is still vital for certain military and industrial users
  • Halon was completely banned in Europe and Australia, other than for critical users like law enforcement and aviation
  • Widely used in Russia and parts of Asia

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