Building on experience: renovation of the SNIFFER gas and fire protection system for the LHC experiments

The LHC SNIFFER system was commissioned in 2006 to protect the personnel working in the large LHC experiment caverns from hazards caused by fire, CO2/flammable gas leaks, and oxygen deficiency. Currently, SNIFFER operates within the ALICE, ATLAS, and LHCb experiments. The system is composed of custom-built modules, each housing an aspiration pump and a combination of sensors tailored to the specific needs of each experiment. Sensor control units are connected to a central control PLC via a PROFIBUS link. The SNIFFER system enables air sampling and analysis from the most remote locations within the LHC experiments, including inside the detectors, using a dedicated air piping network. After nearly 20 years of continuous service, a complete renovation has become necessary. The aim of the modernization project is to address the identified shortcomings, resolve the obsolescence of key components, and significantly reduce the overall cost of system ownership and maintenance. The new system, known as SNIFFER NG (New Generation) is designed to guarantee the safety of personnel in the LHC experiments up to the announced end of operation of the HL-LHC era. This paper presents the new design philosophy, the rationale behind the selected design choices based on the operational experience gathered over the past two decades, and the key challenges associated with the development and deployment of the new system.