When cable trays pass through walls or floors, seal openings using fire-rated penetration sealing materials. Do not modify or damage the tray coating or structure during use. If any abnormality is detected. The proper coating and acceptance of fireproof cable trays are essential for long-term performance and safety. 2 of BS 7671 highlights the need for sealing such systems where they penetrate an element of a building's construction. The requirements of Regulation Group 527. 2 and the relevant Building Regulations are intended to preserve: – fire separation between areas of the. One requirement in NEC ® 725.