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Blazing trails: CMS cavern evacuation paves the way for future safety design

How an evacuation of the CMS experimental cavern has provided invaluable human behaviour data to improve emergency preparedness for complex underground facilities


CERN strives for excellence in safety matters, with a commitment to continuous improvement in the field. Emergency preparedness is a priority for the Organization as it is a key element in its aim to protect both people participating in its activities and its installations. In this context, regular evacuation exercises of all accelerator and experimental areas are a regulatory requirement and part of the CERN-wide safety objectives.

On a warm, sunny day in February 2024, 48 people were going about their daily work in the CMS cavern, unaware that an evacuation exercise, which had been carefully planned for several months, was about to take place. Such exercises are crucial for facility users and rescue teams to gain familiarity with emergency procedures in various contexts and settings. When the alarm sounded, all 48 people reacted calmly, reaching the assembly point quickly and safely. It was a pleasing result for CMS and, apart from the important lessons learned from the exercise, additional data was gathered to improve not only evacuation procedures but also the design of installations in order to make emergency plans even more effective.

This exercise was part of a pilot collaboration between CMS Safety, the HSE Fire Safety Engineering (FSE) team and the Fire Safety Engineering division of Lund University in Sweden, which took this opportunity to maximise the usefulness of the evacuation to study human behaviour in emergency situations.

Comprising reports by undercover observers, questionnaires and footage from security cameras (used in full compliance with Operational Circular No. 11 to ensure anonymity), the data collected provides many useful insights into evacuation dynamics, occupant characteristics and perceptions of safety procedures.

This information is essential for the design of and emergency planning for subterranean experimental areas. As opposed to the design of buildings located above ground, which follows national safety standards, the design of underground areas relies extensively on computer modelling. Using various parameters, it is possible to simulate human behaviours in the event of an emergency to predict the effectiveness of a real-life evacuation.

In this pilot study, the Lund and FSE teams will use the CMS evacuation data to identify unique human behaviours observed in emergencies in complex underground environments. This will expand the current knowledge base and help build a database of specific input parameters to fine-tune and/or validate existing evacuation models.

Ultimately, this methodology will be instrumental not only to improve CERN’s emergency response in the caverns, but also to influence the safety design across current and future complex facilities, at CERN and beyond.