The National standard is very clear regarding cable support:
“Cables which are directly fixed to surfaces should be neatly run and securely fixed at suitable intervals”.
Cables can be run in the open as long as they are securely fixed and supported. Any cable installed inside a ceiling void should still be securely fixed and NOT laid loosely on top of the ceiling tiles.
“The circuits of fire alarm systems need to be segregated from the cables of other circuits to minimize any potential for other circuits to cause malfunction of the fire alarm system”.
Fire alarm cables should be provided with their own routes and kept clear from other cables as much as it is possible. Avoid mains current carrying cables, do not secure fire alarm cables to mains cable or run parallel
on the same trays as them.
“To avoid the risk of mechanical damage to fire alarm cables, they should not be installed within the same conduit as the cables of other services”.
Fire detection cables installed in conduit must be on their own and not shared with cables of other services.
“Protection may be provided by laying cable on a tray, protecting it by burying in the structure of the building, or by installation in conduit, ducting or trunking”.
Cables can be run in conduit, on cable ladders, in cable trays, in cable trunking or recessed into the walls.
Many choices are available for the installer.
“Methods of cable support should be non-combustible and such that circuit integrity will not be reduced below that afforded by the cable used, and should withstand a similar temperature and duration to that of the cable, while maintaining adequate support”
Cables cannot be fixed with PVC cable ties, installed in PVC trunking. If the cables are installed in PVC conduit, the conduit supports must be non-combustible and spaced no more that 500 mm apart.