Abstract: Based on the investigation and analysis of the working conditions of in-service fixed fire extinguishing systems such as gas fire extinguishing system and sprinkler system, this paper clarifies the factors affecting the failure of fixed fire extinguishing system to implement effective fire extinguishing at the fire site, and puts forward the possibility and ideas of extended fire investigation from the aspects of product producers, design, construction and maintenance, management and maintainers. It provides technical support for expanding and enhancing the means and scope of fire investigation.

Key words: fixed fire extinguishing system; fire investigation; extended investigation