IEC 61537 limits cable tray fill to 50% for power cables specifically to maintain air gaps that slow fire propagation and allow adequate heat dissipation during normal operation. This worked example. The National Electrical Code (NEC) lays out specific guidelines regarding which cables are permitted for use in these trays, ensuring safety and compliance with industry standards. Route. ucts; however, as an alternative DIN 4102-12 can be used. This is a test for electric cable systems that are required to maintain circuit integrity, so is therefore written around and is dependent on the cables themselves, but containmen of 90 minutes (the maximum time covered by DIN 4102-12). The use and installation of cable trays is covered by legally enforceable OSHA regulations in 29 CFR 1910.