Fire Safety Science Digital Archive

Terylene ducting coated with neoprene can be used to convey hot, moist, inert gas and high expansion foam; uncoated terylene ducting can be used for diffusing gas or conveying high expansion foam. Such ducting of 30 in (0.77 m) diameter can be prevented from collapsing or whipping by the incorporation of a wire helix and by tensioning the duct by ties secured to the duct. If the diameter of the ducting is increased to 4 ft 6 in (1.4 m), it may be made from lightweight fabric with lightweight reinforcement, because the stresses resulting from conveying a given rate of flow of gas are greatly reduced from those found with 30 in (0.77 m) ducting.