Items where Subject is "Section 09: Protection of openings and fire‑stopping"
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- Section 09: Protection of openings and fire‑stopping (35)
Book Section
Every joint, imperfect fit and opening for services through a fire-separating element should be sealed with fire-stopping to ensure that the fire resistance of the element is not impaired. Fire-stopping delays the spread of fire and, generally, the spread of smoke as well.
In mixed use buildings, non-domestic kitchens, car parks and plant rooms should have separate and independent extraction systems. Extracted air should not be recirculated.
Under fire conditions, ventilation and air-conditioning systems should be compatible with smoke control systems and need to be considered in their respective design.
If air handling ducts pass through fire-separating elements, the fire performance of the elements should be maintained using one or more of the following four methods. In most ductwork systems, a combination of the four methods is best.
a. Method 1 – thermally activated fire dampers.
b. Method 2 – fire resisting enclosures.
c. Method 3 – protection using fire resisting ductwork.
d. Method 4 – automatically activated fire and smoke dampers triggered by smoke detectors.
Further information on fire resisting ductwork is given in the ASFP Blue Book.
Where ducts pass between fire-separating elements to serve multiple flats or dwellings, fire dampers or fire and smoke dampers should be actuated by both of the following.
a. Smoke detector-controlled automatic release mechanisms.
b. Thermally actuated devices.
Methods 1 and 4 should not be used for extract ductwork serving kitchens. The likely build-up of grease within the duct can adversely affect dampers.
Method 1 should not be used for extract ductwork passing through the enclosures of protected escape routes (Diagrams 9.3 and 9.4), as large volumes of smoke can pass thermal devices without triggering them.
An ES classified fire and smoke damper which is activated by a suitable fire detection system (method 4) may also be used for protected escape routes.
Both fire dampers and fire and smoke dampers should be all of the following.
a. Sited within the thickness of the fire-separating elements.
b. Securely fixed.
c. Sited such that, in a fire, expansion of the ductwork would not push the fire damper through the structure.
Access to the fire damper and its actuating mechanism should be provided for inspection, testing and maintenance.
Pipes passing through a fire-separating element, unless in a protected shaft, should meet one of the alternatives A, B or C below.
Fire dampers should meet both of the following conditions.
a. Conform to BS EN 15650.
b. Have a minimum E classification of 60 minutes or to match the integrity rating of the fire resisting elements, whichever is higher.
Fire and smoke dampers should meet both of the following conditions.
a. Conform to BS EN 15650.
b. Have a minimum ES classification of 60 minutes or to match the integrity rating of the fire resisting elements, whichever is higher.
Smoke detectors should be sited so as to prevent the spread of smoke as early as practicable by activating the fire and smoke dampers. Smoke detectors and automatic release mechanisms used to activate fire dampers and/or fire and smoke dampers should conform to BS EN 54-7 and BS 5839-3 respectively.
Further information on fire dampers and/or fire and smoke dampers is given in the ASFP Grey Book.
The wall of a flue, duct containing flues or appliance ventilation duct(s) should have a fire resistance (REI) that is at least half of any compartment wall or compartment floor it passes through or is built into (Diagram 9.5).
In addition to any other provisions in this section, both of the following conditions should be met.
a. Joints between fire-separating elements should be fire-stopped.
b. Openings through a fire resisting element for pipes, ducts, conduits or cable should be all of the following.
i. As few as possible.
ii. As small as practicable.
iii. Fire-stopped (allowing thermal movement in the case of a pipe or duct).
NOTE: The fire-stopping around fire dampers, fire resisting ducts, fire and smoke dampers and smoke control ducts should be in accordance with the manufacturer or supplier’s installation instructions.
Materials used for fire-stopping should be reinforced with (or supported by) materials rated class A2-s3, d2 or better to prevent displacement in both of the following cases.
a. Where the unsupported span is greater than 100mm.
b. Where non-rigid materials are used (unless subjected to appropriate fire resistance testing to show their suitability).
Proprietary, tested fire-stopping and sealing systems are available and may be used. Different materials suit different situations and not all are suitable in every situation.
Other fire-stopping materials include the following. a. Cement mortar. b. Gypsum-based plaster. c. Cement-based or gypsum-based vermiculite/perlite mixes. d. Glass fibre, crushed rock, blast furnace slag or ceramic-based products (with or without resin binders). e. Intumescent mastics. These may be used in situations appropriate to the particular material. Not all materials will be suitable in every situation.
Guidance on the design, installation and maintenance of measures to contain fires or slow their spread is given in Ensuring Best Practice for Passive Fire Protection in Buildings produced by the Association for Specialist Fire Protection (ASFP).
Further information on generic systems, their suitability for different applications and guidance on test methods, is given in the ASFP Red Book.
Provide a proprietary, tested sealing system that will maintain the fire resistance of the wall, floor or cavity barrier.
Where a proprietary sealing system is not used, fire-stop around the pipe, keeping the opening for the pipe as small as possible. The nominal internal diameter of the pipe should not exceed the relevant dimension given in Table 9.1. The diameter given in Table 9.1 for pipes of specification (b) used in situation 2 or 3 assumes that the pipes are part of an above-ground drainage system and are enclosed as shown in Diagram 9.1. If they are not, the smaller diameter given for situation 5 should be used.
A pipe with a maximum nominal internal diameter of 160mm may be used with a sleeve made out of a high melting point metal, as shown in Diagram 9.2, if the pipe is made of one of the following.
a. Lead.
b. Aluminium.
c. Aluminium alloy.
d. Fibre-cement.
e. uPVC (pipes should also comply with either BS 4514 or BS 5255).
A high melting point metal means any metal (such as cast iron, copper or steel) which, if exposed to a temperature of 800°C, will not soften or fracture to the extent that flame or hot gas will pass through the wall of the pipe.
Ductwork should not help to transfer fire and smoke through the building. Terminals of exhaust points should be sited away from final exits, cladding or roofing materials achieving class B-s3, d2 or worse and openings into the building.
Ventilation ducts supplying or extracting air directly to or from a protected stairway should not also serve other areas. A separate ventilation system should be provided for each protected stairway.
A fire and smoke damper should be provided where ductwork enters or leaves each section of the protected escape route it serves. It should be operated by a smoke detector or suitable fire detection system. Fire and smoke dampers should close when smoke is detected. Alternatively, the methods set out in paragraphs 9.16 and 9.17 and Diagrams 9.3 and 9.4 may be followed.
In a system that recirculates air, smoke detectors should be fitted in the extract ductwork before both of the following.
a. The point where recirculated air is separated from air to be discharged to the outside.
b. Any filters or other air cleaning equipment.
When smoke is detected, detectors should do one of the following.
i. Cause the system to immediately shut down.
ii. Switch the ventilation system from recirculating mode to extraction to divert smoke to outside the building.
Image
NOTES:
1. The enclosure should meet all of the following conditions.
a. Be bounded by a compartment wall or floor, an outside wall, an intermediate floor or a casing(see specification at 2 below).
b. Have internal surfaces (except framing members)of class B-s3, d2 or better.
Note: when a classification includes ‘s3, d2’, this means that there is no limit set for smoke production and/or flaming droplets/particles).
c. Not have an access panel which opens into a circulation space or bed room.
d. Be used only for drainage or water supply or vent pipes for a drainage system.
2.The casing should meet all the following conditions.
a. Be imperforate except for an opening for a pipe
or an access panel.
b. Not be of sheet metal.
c. Not have fire resistance less than E 30 (including any access panel).
3.The opening for a pipe, in either the element of structure or the casing, should be as small as possible and fire-stopped around the pipe.
See para 9.4 and Table 9.1
NOTES:
1. Any metal (such as cast iron, copper or steel) which, if exposed to a temperature of 800°C, will not soften or fracture to the extent that flame or hot gas will pass through the wall of the pipe.
2. uPVC pipes that comply with either BS 4514 or BS 5255.
3. These diameters are only in relation to pipes that form part of an above-ground drainage system and are enclosed as shown in Diagram 9.1. In other cases, the maximum diameters given for situation 5 apply.
NOTES:
1.Make the opening in the structure as small as possible and provide fire-stopping between pipe and structure.
2.See Table 9.1 for materials specification.
3. The sleeve should be class A1 rated.
See para 9.5
NOTE:
Ventilation ducts which serve other parts of the building should not supply or extract air directly to or from a protected escape route.
Ductwork enclosed in fire resisting construction classified EI X in accordance with BSEN13501-2 (fire exposure from the duct side), or fire resisting ductwork classified EIS X in accordance with BS EN 13501-3, where X is the fire resistance rating (in minutes) of the walls of the protected escape route
See para 9.16
ES leakage rated fire and smoke damper conforming to BS EN 13501-3/BS EN 1366-2
Smoke detection system in accordance with BS 5839-1 to activate ES damper
Ductwork passing through protected escape routes–method 4
NOTE:
Ventilation ducts which serve other parts of the building should not supply or extract air directly to or from a protected escape route.
See para 9.16
a. Flue passing through compartment wall or floor
b. Flue built into compartment wall
Flue walls should have a fire resistance of at least one half of that required for the compartment wall or floor and be of class A1construction.
In each case flue walls should have a fire resistance of at least one half of that required for the compartment wall and be of class A1 construction.
See para 9.23