An 'OD pipe fire' likely refers to issues or specifications related to the Outside Diameter (OD) of pipes used in fire protection systems, such as fire sprinklers or hydrants, where OD is crucial for fitting seals, system capacity, and firestopping, with solutions like fire-retardant materials (EPP) or specific pipe schedules (e.g., 165mm OD for C-Class) used to ensure safety and performance. Problems like blockages or damage in these pipes can compromise entire systems, highlighting the need for maintenance and correct sizing based on OD. Key Aspects of OD in Fire Pipes: Firestopping: Fire seals around pipes in walls/floors depend on the OD to effectively block fire spread, with thicker-walled pipes (smaller ID for same OD) needing specific seals. System Design: Pipe OD and wall thickness (Schedule) determine flow capacity for fire suppression, with larger OD pipes needed for longer runs or more heads. Materials: Fire-rated pipes (steel, specific plastics) are chosen for high heat resistance, often with features like black coating or fire-retardant foam (EPP) for thermal insulation