A review of the safety data gathered via the BSR's Mandatory Occurrence Reporting system. What are the most frequently reported issues and what do they tell us about systemic risks?. Mandatory Occurrence Reporting: Unpacking the BSR's Critical Safety Data The UK fire safety landscape is undergoing an unprecedented transformation, driven by the Building Safety Act 2022 (BSA 2022). A cornerstone of this new regime is the mandatory occurrence reporting (MOR) system, which compels duty holders for higher risk buildings (HRBs) to report specified safety occurrences to the Building Safety Regulator (BSR). This new data stream, while still in its nascent stages, is beginning to reveal critical trends and systemic risks that demand urgent attention from fire engineers, building owners, and regulators alike. Our deep dive into the initial reporting data highlights the most frequently flagged issues, offering a stark insight into the challenges facing the built environment and the proactive measures being taken by the BSR to address them. Background The Grenfell Tower tragedy irrevocably altered the UK's approach to building safety. The subsequent Hackitt Review identified significant systemic failures, including a lack of clear accountability, fragmented regulatory oversight, and insufficient data on building performance and safety incidents. The BSA 2022 emerged as the legislative response, aiming to create a more robust, transparent, and accountable system. Central to this new framework is the BSR, established within the Health and Safety Executive (HSE). The BSR's remit extends beyond traditional enforcement, encompassing the oversight of building safety for HRBs throughout their lifecycle, from design and construction to occupation. A key tool in achieving this oversight is the MOR system. Under the BSA 2022, principal accountable persons (PAPs) and accountable persons (APs) for occupied HRBs are legally required to report certain safety occurrences to the BSR. These occurrences are broadly defined as events that could cause a significant risk to the safety of people in or about an HRB. This can range from structural failures and fire safety system malfunctions to issues with external wall systems and even significant breaches of building safety regulations. The intention is to create a comprehensive database of incidents, allowing the BSR to identify emerging risks, issue targeted safety alerts, and inform future regulatory and guidance developments. This proactive data driven approach marks a significant departure from previous reactive models. Key Developments Analysis of the initial MOR data, while not yet statistically mature enough for definitive long term conclusions, reveals several recurring themes and areas of concern that the BSR is actively monitoring. The most frequently reported issues can be broadly categorised as follows: 1. Fire Safety System Malfunctions: Unsurprisingly, issues with active and passive fire safety systems dominate the reports. This includes failures of automatic fire detection and alarm systems (AFDAS), sprinkler system faults (e.g., pipework leaks, pump failures, inadequate water pressure), smoke control system malfunctions (e.g., failed dampers, inoperable fans), and issues with emergency lighting. A common thread here is often a lack of adequate maintenance or testing, highlighting potential non compliance with the Regulatory Reform (Fire Safety) Order 2005 (RRO 2005) and British Standards such as BS 9991 and BS 9999. Reports frequently detail instances where systems either failed to activate as intended during an incident or were found to be non operational during routine checks. 2. External Wall System Defects: Despite significant efforts post Grenfell, problems with external wall systems (EWS) continue to be a prominent feature in MORs. This includes the discovery of combustible materials, inadequate fire breaks, missing or poorly installed cavity barriers, and issues with the overall fire performance of cladding systems. These reports often stem from intrusive surveys conducted as part of the Building Safety Case development or during remediation works. The BSR is particularly keen on understanding the prevalence and nature of these defects, especially in buildings not yet subject to comprehensive remediation, as they represent a significant residual risk. 3. Structural Integrity Concerns: While less frequent than fire safety system issues, reports concerning structural integrity are of high concern. These range from minor structural defects identified during surveys to more significant issues impacting load bearing elements or stability. Such reports often trigger immediate action and engagement with structural engineers. The BSR is particularly interested in any trends that might indicate systemic issues related to design, construction quality, or material degradation. 4. Breaches of Building Safety Regulations and Management Failures: A notable category of reports rela