International High-Energy Physics Technical Safety Forum

This paper present the results of a risk analysis on the large underground halls housing the Atlas and CMS, conducted in order to evaluate the maximum credible fire accident scenarios. The simulations study the development of fires located in different position in the underground halls, their timing, and the interaction with a population randomly scattered in the halls and moving towards the exits. People flow, progressive inhibition of the exits due to smoke movement, formation of queues, maximum temperature and visibility of the smoke in the initial stage are evaluated. Available safe egress time and required minimum egress time are estimated and compared in order to assess if the safety conditions are met.