Halocarbon clean agents extinguish fires primarily by interrupting the chemical chain reaction of combustion. When exposed to the high temperatures present in a fire, these chemical agents undergo thermal decomposition. This process breaks down the agent and results in the formation of halogen acids, with hydrogen fluoride (HF) being the most significant byproduct for fluorinated agents. Hydrogen fluoride is a toxic and corrosive gas that, upon contact with moisture in the eyes or respiratory tract, forms hydrofluoric acid. This acid is a severe irritant and poses a significant life safety hazard, which is a primary consideration in system design and post-discharge procedures.

A. Inert clean agents extinguish fires by reducing oxygen concentration; they are chemically stable and do not decompose to form acids.

B. Carbon dioxide is a stable molecule that extinguishes by oxygen displacement and cooling; it does not thermally decompose into an irritant acid.

C. Water extinguishes primarily by cooling (heat absorption); it does not break down into an acidic compound during fire extinguishment.

1. NFPA 2001, Standard on Clean Agent Fire Extinguishing Systems, 2022 Edition. Section A.5.1.2.1 states, "The discharge of halocarbon clean agents to extinguish a fire can create a hazardous situation for personnel... from the products of decomposition that result from exposure of the agent to the fire... The primary decomposition product of the fluorinated and iodinated halocarbon agents is hydrogen fluoride (HF)."

2. SFPE Handbook of Fire Protection Engineering, 5th Edition. Chapter 55, "Halogenated Agent Extinguishing Systems," Section 55.4.3, "Decomposition Products." This section details that "When halocarbon fire suppressants are exposed to flames, they will decompose to some extent to form halogen acids (HF, HCl, HBr)..." It further clarifies that hydrogen fluoride (HF) is the predominant decomposition product for fluorinated agents.

3. Cote, A. E. (Ed.). (2008). Fire Protection Handbook, 20th Edition, Volume II. National Fire Protection Association. Section 18, Chapter 3, "Clean Agents," page 18-42. The text explains, "The major toxic products of decomposition of the halocarbon agents are the halogen acids... For the fluorinated agents, the major product is hydrogen fluoride (HF)."