ABC Dry Chemical Extinguisher: NFPA 10 Distribution, Testing and Rating

Portable fire extinguishers are mandatory in every building. ABC dry chemical (monoammonium phosphate, NH4H2PO4) fits 90 percent of facilities as a universal choice. NFPA 10 (Standard for Portable Fire Extinguishers) defines travel distance, rating, hydrostatic testing and monthly inspection.

Fire Classes

• A: solids (wood, paper, textile)
• B: flammable liquid (gasoline, thinner)
• C: electrical (panels, switchgear)
• D: metal (magnesium, sodium) - special dry salts
• K: kitchen oil (saturated oil) - wet chemical

ABC covers three classes universally.

ABC Mechanism

Monoammonium phosphate (MAP):

• Class A: heat decomposes it into metaphosphoric acid coating paper
• Class B: chain reaction interruption (radical scavenging)
• Class C: non-conductive (dielectric)
• Corrosion risk: may damage electronics - clean after

NFPA 10 Rating and Distribution

NFPA 10 Table 6.2.1:

• Light Class A: 2A - 23 m max travel
• Ordinary Class A: 3A - 23 m
• Light Class B (1 L fuel): 5B - 9 m
• Ordinary Class B: 10B - 15 m
• Typical 6 kg ABC: 4A:55B:C rating - office-appropriate

Inspection and Testing

• Monthly visual: pressure gauge, tag, unobstructed
• Annual: certified technician, full service
• Every 6 years: internal inspection, powder-clumping check
• Every 12 years: hydrostatic test (visual + pressure)
• Records: maintain tag and logbook

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