System Types

Non-domestic kitchen extract ductwork is sometimes referred to as grease ducting and should be tested for Type A fire outside and Type B fire inside. Both tests are required to prevent flammable grease from either catching fire when it passes through an adjacent area or, if the grease itself is already alight, causing a fire to start within the adjacent area by radiant heat.

• Non-domestic kitchens must have separate and independent extract systems
• Fire dampers should not be used in kitchen extract ductwork
• As kitchen extract should not be provided with fire dampers, only fire-resisting ductwork should be used when immediate discharge to the outside of the building is not possible.
• Where fire-resisting ductwork is used, it should be a complete system from canopy to atmosphere
• Commercial kitchens should have separate and independent extraction systems and the extracted air should not be recirculated.
• Access doors must be installed at maximum 2 metre intervals where possible and internal surfaces must be smooth to enable easy cleaning of the grease. Self-drilling screws should not be used.
• Care must be taken to ensure combustible deposits in the duct cannot ignite in adjacent compartments.

Ductwork within the kitchen that exhausts directly to the outside of the building does not have to be fire rated. DW144 ductwork can be used, (shown in grey).

Kitchen extract ductwork presents a particular hazard in that combustible deposits, such as grease, are likely to accumulate on its internal surfaces. Therefore, the ductwork needs to resist fire from the inside (Type B) and must be rated for integrity and insulation for the same period of time as the compartment through which it passes from hood to discharge, (shown in blue).

A fire in an adjacent compartment, through which the kitchen extract ductwork is passing, could initiate a fire within the ductwork, which in the absence of fire dampers might prejudice the safety of the kitchen's occupants. For this reason, it should also be tested to fire outside (Type A).

Fans to EN 12101-3 must be used. Refer to BESA DW/172 for fan type.

It is good practice to discharge the ductwork system 2m vertically from the highest point of the building to prevent fire igniting the building structure or other services. Please check local authority regulations.

All fire rated ductwork and penetration seals must be tested to BS:EN 1366-1 including kitchen extract or ductwork with combustible linings test and classified in accordance with BS:EN 13501-3 by a recognised UKAS accredited laboratory.

Note: Final approval must always be obtained from the Project Fire Engineer/fire department prior to commencement of construction.

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Basement enclosed car parks require an extract system suitable for clearing smoke and fumes. Either natural or mechanical methods may be used to ventilate the basement.

The provisions for ventilation of basement car parks in Approved Document B, section 11 satisfy the requirements for venting smoke from any basement used as a car park.

NATURAL VENTILATION

Each storey should be ventilated by permanent openings at each car parking level. The openings can be at ceiling level. The aggregate free vent area should be a minimum of 1/40 of that level's floor area, at least half of which should be provided equally by two opposite walls (1/160 on each side). The remaining free area can be distributed wherever possible.

MECHANICAL SMOKE EXTRACT

If the minimum standard of natural ventilation is not possible, a system of mechanical ventilation should be provided that complies with all of the following.

1. The system should be Independent of any other ventilating system (other than any system that provides day to day ventilation to the car park) and be designed to operate at 10 air changes per hour during fire condition.
2. The system should run in two parts, each of which is:
3. capable of extracting 50% of the rates set out above.
4. ii. able to operate alone or with the other part.
5. iii. provided with an independent power supply capable of operating if the main supply fails.
6. 50% of the outlets should be at high level and 50% at low level.
7. The system should use E, I and S ductwork in accordance with BS EN 1366-8, to retain at least 90% of its cross sectional area throughout the entire system.
8. Fire dampers should not be used in any basement extract system.

For further information on equipment for removing hot smoke, refer to BS EN 12101-3. An alternative method of providing smoke ventilation from enclosed car parks is given in BS 7346-7.

The basement car park extract ductwork system (shown in brown) must be suitable for clearing fumes and smoke from the basement level. The system should normally be rated for a minimum of one hour integrity and maintain at least 90% cross sectional area.

Where the ductwork leaves the compartment from which it serves (shown in blue) it must maintain integrity and insulation fire ratings for the same period of time as the compartment through which it passes.

Fans classified to EN 12101-3 must be used in run and standby configuration.

Any in line equipment such as attentuators, VCD's etc. must be tested.

All fire rated ductwork and penetration seals must be tested to BS:EN 1366 Part 8 and classified in accordance with BS:EN 13501-4 by a recognised UKAS accredited laboratory.

Note: Final approval must always be obtained from the Project Fire Engineer/fire department commencement of construction.

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Ducts crossing escape routes or protected areas should be protected from the effect of fire using methods 2, 3 or 4 from BS9999:2017.

The pressurised air supply duct requires integrity and insulation for fire outside Type A (shown in blue) for the same period of time as the compartment through which it passes.

The ductwork in the final compartment (Escape Lobby) (shown in brown) will require integrity rating for the same period of time as the compartment through which they pass.

Both the normal ventilation supply duct and extract duct follow a route from the riser shaft through the office using the dampers and galvanised sheet steel duct - method 1 of BS 9999 (shown in white).

Ducts that cross in the escape corridor (shown in blue) must be fire rated and will require integrity and insulation for the same period of time as the compartment through which they pass.

The escape route duct will also require at least one fire damper either side of the escape corridor.

All fire rated ductwork and penetration seals must be tested to BS EN 1366-1 and classified in accordance with BS EN 13501-3 by a recognised UKAS accredited laboratory.

Note: Final approval must always be obtained from the Project Fire Engineer/fire department prior to commencement of construction.

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Pressurisation ductwork is the ductwork used as part of a pressurisation system. Typically used in protected stairways, lobbies, corridors and fire fighting shafts. A pressurisation system is a special form of mechanical ventilation which maintains a positive pressure in critical areas to prevent smoke entering from adjacent areas.

• Pressurisation ducts must be able to maintain an air supply to critical areas for the duration of the fire.
• Air supply must be maintained, fire dampers cannot be used.
• All ductwork penetrating fire compartments must be fire rated in order to maintain compartmentation.
• Fire dampers must not be used within these systems.

Ductwork (shown in blue) a minimum rating of one hour for integrity and insulation to resist fire from outside (Type A).

Ductwork (shown in cream) in the final compartment requires a minimum rating of one hour for integrity to resist fire from outside (Type A).

Fans to EN 12101-3 must be used.

All fire rated ductwork and penetration seals must be tested BS EN 1366-1 and classified in accordance with BS EN 13501-3 by a recognised UKAS accredited laboratory.

Note: Final approval must always be obtained from the Project Fire Engineer/fire department prior to commencement of construction.

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Basements require an extract system suitable for clearing smoke and fumes. Either natural or mechanical methods may be used to ventilate the basement.

NATURAL VENTILATION

Smoke outlets should be sited at high level of the space they serve and be distributed evenly around the perimeter of the building. If a basement is compartmented, each compartment should have one or more smoke outlets, rather than indirect venting.

• The combined clear cross-sectional area of all smoke outlets should not be less than 1/40th of the floor area of the storey they serve.
• Separate outlets should be provided from places of special fire hazard.
• If the outlet terminates at a point that is not readily accessible, it should be kept unobstructed and should only be covered with a non-combustible grille or louvre
• If the outlet terminates in a readily accessible position, it may be covered by a panel, stallboard or pavement light which can be broken out or opened. The position of such covered outlets should be suitably indicated.
• Outlets should not be placed where they would prevent the use of escape routes from the building.

MECHANICAL SMOKE EXTRACT

A system of mechanical extract may be provided as an alternative to natural venting to remove smoke and heat from basements, providing that the basement storey(s) are fitted with a sprinkler system in accordance with Appendix E of Approved Document B. Sprinklers do not need to be installed on the other storeys unless they are needed for other reasons.

• The air extraction system should give at least 10 air changes per hour and should be capable of handling gas temperatures of 300°C for not less than one hour. It should come into operation automatically on activation of the sprinkler system; alternatively activation may be by an automatic fire detection system which conforms to BS 5839-1 (at least L3 standard).
• Fire dampers should not be used in any basement extract system.
• Ductwork must retain at least 90% of its cross sectional area throughout the entire system

The basement extract ductwork system (shown in brown) must be suitable for clearing fumes and smoke from the basement level. The system should normally be rated for a minimum of one hour integrity and maintain at least 90% cross sectional area.

Where the ductwork leaves the compartment from which it serves (shown in blue) it must maintain integrity and insulation fire ratings for the same period of time as the compartment through which it passes.

Fans to EN 12101-3 must be used in run and standby configuration.

Any in line equipment such as attenuators, VCD's etc. must be tested.

All fire rated ductwork and penetration seals must be tested to BS:EN 1366 Part 8 and classified in accordance with BS:EN 13501-4 by a recognised UKAS accredited laboratory.

Note: Final approval must always be obtained from the Project Fire Engineer/fire department before commencement of construction.

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Ductwork systems extracting fine powders or chemical solvents are considered to have an increased fire risk.

• Areas of high risk will require separate and independent extract systems
• Such areas would typically include: boiler rooms, solvent extracts, specialist dust extracts and lift ventilation ducts.

The extract ductwork system (shown in brown) must be suitable for clearing fumes and smoke. The system should normally be rated for a minimum of one hour integrity and maintain at least 90% cross sectional area.

Where the ductwork leaves the compartment from which it serves (shown in blue) it must maintain integrity and insulation fire ratings for the same period of time as the compartment through which it passes.

All fire rated ductwork and penetration seals must be tested to BS EN 1366-8 and classified in accordance with BS EN 13501-4 by a recognised UKAS accredited laboratory.

Note: Final approval must always be obtained from the Project Fire Engineer/fire department prior to commencement of construction.

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Service enclosures should be tested for both fire inside (Type B) and fire outside (TypeA) to meet the BS EN 1366-5:2021 standard.

In addition, the enclosures must be tested:

·     in both horizontal and vertical orientations.

·     with the maximum size intended in practice.

·     With a loading representative of the service loading.

The FPL05 service enclosure satisfied all test criteria for integrity and insulation for 120 minutes, preventing a temperature increase of 140°C as an average or 180°C above ambient at any location.

The FPL05 service enclosure satisfied all test criteria for integrity and insulation for 120 minutes, preventing a temperature increase of 140°C as an average or 180°C above ambient at any location.

Supplied in modular sections the enclosures are installed by Third Party AccreditedInstallers, the services being fitted to the lid section by the relevant trade contractors. The lid section is supplied with fully integrated support channels for this purpose, with the underside being fitted to fully enclose the services.

The enclosed services are protected from the effects of an external fire and additionally, in the event of a fire inside the enclosure, fire is prevented from break out into adjacent compartments.

This ensures that compartmentation is maintained facilitating the safe evacuation of occupants and access for rescue and fire-fighting services.

High voltage cable enclosures are tested to meet BS EN 1366-5:2021 and in addition, to the revised BS 8519:2020,

In addition to the requirements of EN1366-5, T3 thermocouples are required on the horizontal fire outside (Type A) test, on each internal face of the enclosure midway inside the furnace.

The FPLHV enclosure satisfied all test criteria for integrity and insulation for 120minutes, preventing a temperature increase of 140°C as an average or 180°C at any location, including the T3 thermocouples mentioned above; a specific requirement of the latest 2020 edition of BS 8519.

Prefabricated in modular sections to ease installation, the cables are fitted to the lid section by the electrical contractor, connected via integral internal channels, before the closing underside is fitted to fully enclose the cables.

The cables are protected from an external fire, preventing overheating of the cables and a drop in conductivity, thereby ensuring that life safety services continue to function, enabling safe evacuation of occupants and access for rescue and fire-fighting services.

Additionally, in the event of a fire inside the enclosure, the associated EN 1366 part 5 fire inside test demonstrates that fire is prevented from breakout into compartments through which the enclosure passes.