This design note adopts a 300 mm horizontal air-gap separation between primary and secondary life-safety trays on roofs, based on these regulatory requirements and established UK guidance. BS 7671:2018 +A2:2022 states: “Circuits of safety services shall be independent of other. UK electrical and fire safety standards do not prescribe a fixed minimum separation distance for roof-mounted life-safety cable trays. However, BS 7671, BS 8519, and BS 5839 collectively establish that life-safety circuits must be installed on dedicated containment and be either separated by. When installing two cable trays in parallel at the same height, the distance between them should be no less than 0. This spacing is crucial for adequate maintenance access, ease of inspection, and ensuring proper airflow for effective heat dissipation. It also helps reduce the risk of. The cable support lengths and fittings can basically be designed as cable trays, cable ladders or mesh cable trays, in which cables are routed. Fittings can, on the one hand, be used for horizontal or vertical changing of the routing direction or, on the other, to change the height or width of the. The NEC requires that cable trays must be supported by members at an interval specified by the cable tray manufacturer, but not more than 5 feet for horizontal runs to support the weight of the cables and other loads. The NEC has a requirement for ladder-type cable trays. For 6 meter tray that would be approximately 1. Cable ladder systems and cable tray systems shall be manufactured in accordance with BS EN 61537, channel support.