<p>Perfluorohexanone (C₆F₁₂O, FK-5-1-12) is a fluorinated fire-extinguishing agent with high suppression efficiency and distinctive engineering applicability. However, systematic research on the flow mechanisms and engineering design methods of C₆F₁₂O fire-extinguishing pipe networks remains limited. This paper develops a theoretical pipe-network model for gaseous fire-extinguishing systems and conducts C₆F₁₂O discharge experiments. The effects of the expansion coefficient on the discharge process and flow characteristics are examined, and a recommended range is proposed. To address practical engineering design needs, a general engineering method for fire-extinguishing pipe networks is proposed without relying on empirical parameters. The results show that the expansion coefficient significantly affects the discharge duration, and <i>γ</i> = 1.15–1.20 is recommended for engineering calculations. The operating process of gaseous fire-extinguishing systems can be divided into four typical stages. Theoretical predictions agree well with experimental measurements qualitatively, and the quantitative deviations are within 20%. For both perfluorohexanone and heptafluoropropane (C₃HF₇) systems, the proposed pipe-network engineering method yields results highly consistent with the theoretical model, with errors controlled within 10%. The algorithm is highly accurate and broadly applicable to the engineering calculation and design of various gaseous fire-extinguishing systems. This study provides a theoretical foundation and methodological support for the standardized design of gaseous fire-extinguishing systems using fluorinated agents.</p>