aspe00_fire rated & smoke outlet ductwork (blue book)

8/7/2019 ASPE00_Fire rated & smoke outlet ductwork (Blue Book)

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F i r e r a t e d a n d s m o k e o u t l e t

d u c t w o r k

An industry guide to design and installation

Association House, 99 West Street, Farnham, Surrey GU9 7EN

t: 01252 739142 f: 01252 739140 www.asfp.org.uk

FR&SODUCTWORK Page iJune 2000
http://www.asfp.org.uk/http://www.asfp.org.uk/


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FOREWORD

I am pleased to have been asked to introduce this new publication from theAssociation for Specialist Fire Protection.

This publication from ASFP should be warmly welcomed by designers, insurers andend-users alike. The prevention of fire spread through ducted systems is of criticalimportance, as evidenced by a number of recent serious fire losses. This documentprovides details and gives recommendations not previously covered in otherstandards or codes of practice and should make a significant contribution to improvedfire safety.

Contained within the document are sections on the different types of system and theirfunction, information on all the relevant legislation, standards and codes of practiceand notes on penetration seals and support systems. BRE particularly recognises theimportance of using fire-rated ductwork for air distribution and smoke extractionapplications, and is particularly pleased to see these topics addressed here. Ourcommitment in this area is illustrated by their inclusion in the LPC Design Guide forthe Fire Protection of Buildings, the UK insurers' guidance document on building fireprotection, which BRE will continue to maintain on their behalf.

The merger of BRE and LPC offers exciting new opportunities for working inpartnership with ASFP and other experts from the fire industry to promote highstandards of fire protection. BRE is sure that this Guide will become an essentialreference work within the industry and congratulates ASFP on producing anotherexcellent technical document.

Dr Jeremy HodgeManaging Director, Fire and Risk Sciences, BRE

FR&SODUCTWORK Page iiJune 2000


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Association for Specialist Fire Protection (ASFP)Association House, 99 West Street, Farnham, Surrey GU9 7ENt: +44(0)1252 739142 f: +44(0)1252 739140 www.asfp.org.uk

The Association was formed in 1976, and currently represents the majority of UKcontractors and manufacturers of specialist fire protection products, with associatemembers representing regulatory, certification, testing and consulting bodies.

ASFP seeks to increase awareness and understanding of the nature of fire and thevarious forms, functions and benefits provided by passive fire protection.

It is willing to make available its specialist knowledge on all aspects of fire protectionand can assist specifiers and main contractors in identifying products suitable forspecific requirements, both in the UK and overseas.

ACKNOWLEDGEMENT

This document has been prepared by the Fire Rated and Smoke Outlet Ductwork

Working Group of the ASFP, and the work of the members of that Committee, asfollows, is gratefully acknowledged:

R H Earle, Chairman FR&SOD Working Group, Loss Prevention Council;C W Aitken, McCartney Fire Protection Ltd;

P W Crewe, Warrington Fire Research Centre;A P Flint, Cape Calsil Systems Ltd (Durasteel);

B A James, Fire Protection Ltd;N J MacDonald, Promat Fire Protection Ltd;

J E Murray, Senior Hargreaves;N Ralph, Rockwool Ltd;

R B Smith, ASFP Technical Officerand B S Webster, Cape Calsil Systems Ltd (Durasteel)

Although care has been taken to ensure, to the best of our knowledge, that all dataand information contained herein is accurate to the extent that it relates to eithermatters of fact or accepted practice or matters of opinion at the time of publication,the Association for Specialist Fire Protection accepts no responsibility for any errorsin or misinterpretations of such data and/or information or any loss or damage arisingfrom or related to its use.

Compliance with this ASFP document does notof itself confer immunity from legal obligation.

Association for Specialist Fire Protection 2000ISBN: 1 870409 15 9

FR&SODUCTWORK Page iiiJune 2000


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SCOPEThis publication is intended to assist the reader in understanding many of theessential details which play a significant part in ensuring that fire rated (whichincludes smoke outlet) ductwork is correctly designed and installed in accordancewith current UK legislative requirements.

The information given in this guidance note therefore relates to the types andfunctions of fire rated ductwork, and references the Building Regulations, BritishStandards and Codes of Practice which apply to these specific types of duct.

Detailed information on current UK standard fire resistance and reaction to fire testsis provided, together with recommended methods for appraisal systems for bothdirect and extended fields of application. Guidance is also given in respect of the fireresisting requirements for penetration seals, support systems and ancillary items,with a section relating to limitations.

Drawings of typical BS 476: Part 24 test constructions are reproduced (by kindpermission of the British Standards Institution) and diagrams of types and functionsof various fire rated ductwork systems are included. These are for guidancepurposes only.

The guidance given in this publication specifically refers to fire rated ductwork anddoes not, therefore, include advice on conventional non-fire rated ventilationductwork systems.

CAUTIONARY NOTE TO ALL DUCTWORK DESIGNERS, MANUFACTURERSAND INSTALLERS

Sections of this document emphasise the fact that general purpose ventilation/airconditioning ductwork cannot be utilised as, or converted into, a fire rated ductworksystem unless the construction/materials of the whole system are proven by test orassessment in accordance with the requirements of BS 476: Part 24. In this respectthe section entitled 'Limitations' will be of particular interest to the reader.

FR&SODUCTWORK Page vJune 2000


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1. INTRODUCTION

This publication has been produced to assist those involved in the specification,installation, inspection and verification of Fire Rated Ductwork and to ensure thatminimum performance standards are maintained which will contribute to ensuringthat fire compartmentation systems are not breached prematurely.

Fire Rated Ductwork can be provided either by specialist companies producingproprietary systems, or by treatment to satisfactorily constructed and supported steelductwork with the addition of fire insulating materials. Care must be taken whenchoosing a fire rated ductwork system and checks should be made to ensure that theductwork fire performance meets with the requirements of the relevant application.

Compartment walls and floors will have a prescribed fire resistance period whichmeans that the performance criteria of load-bearing capacity (stability), integrity andinsulation have been met for a duration of 30 to 240 minutes. It is therefore vitallyimportant for fire security that where compartmentation boundaries are penetrated bybuilding services, the fire separation and the performance criteria for the penetratedwall or floor are maintained and, in particular, that all forms of ducting in a buildingshould not become a conduit along which fires may spread to other areas. The fireperformance of a duct which penetrates a fire resisting/separating element requirescareful consideration by specifiers and controlling authorities. The standard periodsof stability and integrity should in all cases be at least equal to those required for thepenetrated element. Controlling authorities have, in certain circumstances, waivedthe insulation requirement or allowed a reduced period of insulation (e.g. where theyconsidered that there was no possibility of combustible materials being in theproximity of the ductwork).

The guidance given in Approved Document B1 (Means of Escape) and B3 (Internal

Fire Spread Structure) of the Building Regulations 1991 for England and Wales refersto BS 5588: Part 9 for alternative ways in which the integrity of compartments may bemaintained where ventilation and air conditioning ductwork penetrate fire separatingelements.

Similar recommendations are given in the Northern Ireland Building Regulations andin the Building Standards (Scotland) Regulations.

Many ventilation ductwork systems offer little or no protection against fire spread andtherefore, when ventilation ductwork penetrates building compartmentation, theguidance of BS 5588: Part 9 should be followed:

i.e. Method 1 Protection using fire dampers;

Method 2 Protection using fire resisting enclosures;

Method 3 Protection using fire resisting ductwork.

Statutory regulations and design codes provide the designer with prescribed periodsof fire resistance to construction elements, which give a safe period for evacuation ofpeople, a safe period for fire fighting and also provide for property protection. It isvitally important for life safety that the fire resistance of the construction element isnot reduced when ductwork is routed through it.

Good practice dictates that fire dampers should not be installed within certainductwork systems in buildings (e.g. kitchen extraction, staircase and lobbypressurisation, lift shaft ventilation, fresh air make up provision, etc.) therefore eitherMethod 2 or Method 3 of BS 5588 Part 9 should be used.

FR&SODUCTWORK Page 1June 2000


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Steel ductwork systems for air movements around buildings are generallyconstructed to the HVCA guide DW/144 (formerly 142) which is a document coveringa wide range of construction standards in the manufacture of sheet metal ductworkfor use in low, medium or high pressure applications and includes various methods of

jointing, stiffening and supporting of the ductwork.

BS 5588: Part 9 paragraph 7.5.1 acknowledges that steel ductwork if satisfactorilyconstructed and supported will be able to provide a high degree of resistance tothe passage of smoke and decomposition products. However, rapid transfer of heatthrough the steel regardless of its thickness prevents the ductwork achieving anydegree of fire resistance without supplementary insulation. A satisfactorilyconstructed and supported steel duct is one proven by test and/or assessmentto BS 476: Part 24.

An alternative to steel systems is self supporting ductwork such as that constructedfrom rigid boards. Supplementary insulation may also have to be considered forthese systems.

In 1987 the British Standards Institution introduced Part 24 of the BS 476 Fire Testseries; a method for determination of the fire resistance of ventilation ducts. Thedocument has an annex which gives guidance on the fire performance criteriarequired for kitchen extract and smoke outlet applications, which differ from therequirements for ventilation ducts. It is therefore vitally important when assessing thesuitability of a proposed system of fire rated ductwork that the performance of theproposed system matches the requirements of the application for which it is required;(e.g. a smoke outlet duct is required to maintain a minimum 75% of the original crosssection when tested to BS 476: Part 24).

It is particularly important, when assessing the suitability of a proposed system of fire

rated ductwork, to give due consideration to factors other than fire that may berequired. These may include:

Seismic qualification of ductwork, support system and penetration sealingmethod;

Pressure/air carrying capacity;

Materials sensitive to thermal shock;

Acoustic performance requirement of the system;

Thermal performance requirement of the system;

Resistance to air flow.

2. DEFINITIONS

For the purpose of this document the following definitions apply.

2.1 Duct/Ductwork

Duct/Ductwork

A system of enclosures of any cross sectional shape for the distribution orextraction of air.



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2.3 General

Compartment

A part of a building, comprising one or more rooms, spaces or storeysconstructed to prevent the spread of fire to, or from, another part of the same

building.Fire Resistance

The ability of a component or construction to satisfy, for a stated period of time,the appropriate criteria specified in the relevant part of BS 476. The followingcriteria are applied to fire rated ductwork.

Stability

The ability of a duct, ductwork and the support system to remain intact andfulfil their intended function for a specified period of time, when tested tothe requirements of BS 476: Part 24 (ISO 6944).

Insulation

The ability of a duct or ductwork to maintain its separating function withoutdeveloping temperatures on its external surface, outside the compartmentin which the fire is present, which exceed:

i) 140C as an average value above ambient and/or

ii) 180C as a maximum value above ambient at any one point

when tested for a specified period of time to the requirements of BS 476:Part 24. (ISO 6944). For kitchen extract ductwork (duct A) theselimitations also apply to the internal surface of the duct within thecompartment in which the fire is present.

Integrity

The ability of a duct or ductwork to remain free of cracks, holes oropenings outside the compartment in which the fire is present for aspecified period of time, when tested to the requirements of BS 476: Part24 (ISO 6944).

Fire Separating Elements

Floors, walls, fire protected shafts (multi-service or dedicated) and otherseparating elements of construction having a period of fire resistance asdetermined in accordance with BS 476: Parts 20, 21 or 22.

Penetration

An aperture through a fire separating element for the passage of a duct orductwork.

Penetration Seal

The system used to maintain the fire resistance of the fire separating element,in accordance with BS 476: Part 24, at the position where there is provision fora duct or ductwork to pass through the element.



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Pressurisation

A method of protecting escape routes against the ingress of smoke bymaintaining the air within them at pressures higher than those in adjacent partsof the building.

Protected shaftA shaft which enables persons, air or objects to pass from one compartment toanother, and which is enclosed with fire-resisting construction.

3. TYPES AND FUNCTIONS

This document does not apply to ducts containing services such as water pipes orelectrical cables. It covers only ductwork that is part of the following systems forhandling air, fumes or products of combustion. Typical examples are illustrated infigures 1-8.

3.1 Mechanical Ventilation Systems

Mechanical ventilation systems are used to extract vitiated or polluted air from abuilding and to supply replacement fresh or conditioned air. The necessary fans andconditioning equipment are generally located in separate plant rooms, often in abasement or on the roof. The distribution of the air involves ductwork which may bevery large, extend throughout the building, penetrate compartment walls and/or floorsand have openings in every space through which it passes.

Without suitable fire precautions, therefore, ventilation ductwork can provide a routeby which fire, smoke and toxic gases are enabled to spread rapidly through abuilding.

3.2 Smoke Extraction Systems

Smoke extraction is the evacuation from a building of products of combustion, suchas smoke and toxic gases, which could otherwise reduce visibility and impair humanfunctions. This facilitates the escape of the building occupants and assists firefighters in locating the seat of the fire and extinguishing it.

In situations where smoke clearance by natural ventilation through windows or otheropenings may be difficult (e.g. in large or deep basements or in high rise buildingswithout openable windows) ductwork is required to conduct the smoke to a suitableoutlet from the building. In cases where the natural buoyancy of the combustion

products is not adequate to ensure the required smoke extraction rate through theductwork, fan assisted systems are used. It may also be necessary to install ductedair inlets as part of the smoke extraction scheme, in order to provide the replacementair.

If the ductwork incorporated in a smoke extraction system is wholly contained withinthe fire compartment, it must at least be capable of resisting the anticipated smoketemperatures generated during the development of a fire. These will generally belower than the temperatures specified in BS 476: Part 24, which are intended torepresent a fully developed fire. However, if the ductwork penetrates a fire resistingbarrier, it must also be capable of providing the relevant fire resistance in a test toPart 24. Further clarification of the fire testing requirements for these two differentsituations is provided in Section 5 of this document Standard Fire Tests. In view ofthe importance of maintaining the design extraction rates during a fire, Part 24 also



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imposes an additional requirement on smoke outlet ductwork (i.e. the retention of atleast 75% of its original cross sectional area during the test).

3.3 Dual Ventilation/Smoke Extraction Systems

These systems serve as a conventional ventilation system under normal conditions,

but are converted to a smoke extraction system in the event of fire, thus providing aneconomical dual system.

3.4 Pressurisation Systems

Pressurisation is a method of restricting the penetration of smoke into certain criticalareas of a building, by maintaining the air within them at pressures higher than thosein adjacent areas. It applies particularly to protected stairways, lobbies and corridors,as smoke within these areas would inhibit escape, and also to firefighting shaftsserving deep basements, because of the difficulties in clearing smoke frombasements.

A pressurisation system is a special form of mechanical ventilation system.However, as the air supply creating the pressurisation must be maintained for theduration of a fire, fire dampers cannot be used within the ductwork to prevent thespread of fire. Any duct or ductwork penetrating fire resisting barriers shouldtherefore be fire resisting.

BS 5588: Part 4 gives guidance on the use of pressurisation in buildings for thepurpose of smoke control.

3.5 Car Park and Kitchen Extraction Systems

Car parks and non-domestic kitchens are required to have separate and independent

extraction systems, because of the polluted nature of the extracted air. As BS 5588:Part 9 recommends that fire dampers should not be installed in extraction ductworkserving car parks or kitchens, any duct or ductwork penetrating fire resisting barriersshould be fire resisting.

Kitchen extraction ductwork presents a particular hazard, in that combustible depositssuch as grease are likely to accumulate on its internal surfaces. A fire in an adjacentcompartment through which the ductwork passes could therefore initiate a fire withinthe ductwork which, in the absence of fire dampers, might prejudice the safety of thekitchen occupants. For this reason, BS 476: Part 24 imposes an additionalrequirement, (i.e. when tested as duct A against external fire) the internal surface ofthe ductwork within the furnace must meet the insulation criteria. It is also essentialthat this particular type of ductwork is provided with access for cleaning, at distancesnot exceeding 3m.



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Figure 1Compartmentation: An example


PROTECTED

S H A F T~

IN LINE WITH DOCUMENT ' B OF THE BUILDING RE GULATIONS

]~ CAVITY BARRIER - - . :m = = = = = ~HL~ = = = = = = = = = = ~ = = = = = = = = = = =t 'F = = ~f ,f = = = = = = = = = =

C8UNG VOID

T' BOllE R 3" HOUSE i ~;j y

OFFICE

CBUNG VOID

~:'l = = = = = = ' = == = = == ft!= = = = = = = = = == = = == == l lf:....t i

C8LING VOID ;

~ = = = = = = = = ~ F = = = = = = = = = = = = = = = = = 9' -p = =~ = = = = = = = =

~ C B U N G

f:i!'Jl!L J FIRE RATED WAU.S

- FIRE RATED FlOORS

CJ NOO-RRE RATED WAllS

PAPE RSTORE

BOILERHOUSE

KITCHEN

i~ PARTITIONS TO BE1 FIRE RATED1 ~

SECTION I A' - I A'N O N~ RATED WALLS

ESCAPE CORR IDOR

PLAN

OFFICEFLOOR

SHOP ANDCOMMERClAI.FLOOR

BASEMENT FlOOR( 10m + BE LCMIGROUND LEVEL )


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Figure 2Types of extract ductwork from multi-cellular buildings


OPTION lNO N FIRE RATED DUCTWORK FITTED WITH FIRE DAMPERS.

NOT SUITABLE TO BE SMOKE EXTRACT

... -----LANTROOM -

f \FIRE DAMPERS

NON FIRE RATED DUCTWORK~ . ... -: . . . . ...

~ - , ou. : . ; . ~ ~, : : r. : ~ - : ; : - : , . . . . . ,

FIRE COMPARTMENT WALLS OR FLOORS EXTENT OF TYPICAL FIRE COMPARTMENT


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DUCTWORKSUITABLE FOR

CLEARING SMOKE,OFTEN l HOURSTABILITY ANDINTEGRITY TOB.S 476 Pt 24

- ISO 6944

RETAININGCROSS SECTIONALAREA OF 75 %

OF DUCT

OPTION 2COMBINATION OF FIRE PROTECTED SHAFT WITH

FIRE RESISTING DUCTWORK, SMOKE

IFIRE DAMPERSAND DUCT RUN-OUTS, SUITABLE AS SMOKE EXTRACT

~ f ~PENETRATION SEALS

TO B.S 476 Pt24 I ISO 6944 _. .... : 1' . , . : ;:;r,.: :.. l ,{i ' , ~ - . , . , . .

FIRE COMPARTMENT WALLS OR FLOORS METHOD 3 FIRE RESISTING DUCTWORK


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DUClWORKSUITABLE FOR

CLEARING SMOKE,OFTEN 1 HOURSTABILI1Y ANDINTEGRI1Y TOB.S 476 p t 24

- ISO 6944RETAINING

CROSS SECTIONALAREA OF 75 %

OF DUCT

OPTION 3FIRE RESISTING DUClWORK WITH SMOKE I FIRE DAMPERS

ANDDUCT RUN-OUTS SUITABLE AS SMOKE EXTRACT

\MOTORISED SMOKE I FIRE DAMPERS

\ f \PENETRATION SEALS

TO B.S 476 Pf24 I ISO 6944



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Figure 5Typical smoke outlet ductwork system


DUCTWORKSUITABLE FOR

CLEARING SMOKE,OFTEN 1 HOURSTABILilYANDINTEGRilYTOB.S 476 pt 24

- ISO 6944RETAINING

CROSS SECTIONALAREA OF 75 %

OF DUCT

OPTION 3

FIRE RESISTING DUCTWORKWITH SMOKE I FIRE DAMPERSAND DUCT RUN-OUTS SUITABLE AS SMOKE EXTRACT

PLANTROOM

f ~0TORISED S M O K ~I FIRE DAMPERS

~ f ~PENETRATION SEALS

TO B.S 476 pt24 I ISO 6944



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Figure 6Typical non-domestic kitchen extract ductwork


ROOF PLANT

COMPARTMENT FLOOR

NON-FIRERATED DUCT

COMPARTMENTWALL

r

SUITABLY FIRE RATED FAN

FIRE RESISTINGDUCT NOTREQUIRED

..

FIREKITCHEN EXTRACTDUCT, STABILITY,INTEGRITY ANDINSULATION RATINGEQUAL TOCOMPARTMENT

WALLS

KITCHEN

NOTE : THERE SHOULD BE NO FIRE DAMPERS WITHINNON DOMESTIC KITCHEN EXTRACT SYSTEMS


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Figure 7Typical pressurisation ductwork system


ROOF PLANT

I \

1 \COMPARTMENT FLOOR

SUITABLY FIRE RATED FAN

PENETRATION SEA LSTO B .S 476 Pt 24ISO 6944

FIRE RESISTINGPRESSURISATIONDUCI STABIUTY,INTEGR ITY ANDINSULATION RATINGEQUAL TOCOMPARTMENT

WAL

LSI FL

OORS

FIRE RESISTING PRESSUR ISAT ION

DUCT

NON-FIRE RATED DUCT

PRESSURISATION SHAFTPRESSUR ISED LOBBY NO T CONSTRUC TED TO METHOD 2


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Figure 8Typical basement car park extract


AS DOCUMENT ' B' OF BUILDING REGULATIONS ( 1991 ) & B.S 5588 Pt 9

FANS DESIGNED TO OPERATE AT 400 C FOR 1 HOUREACH FAN DESIGNED TO RUN AT 50% OF THENORMAL AND SMOKE VOLUMES AND DESIGNEDSO THAT EACH FAN CAN OPERATE SINGULARLYAND SIMULTANEOUSLY

PENETRATION SEALAS TESTEDTO BS476 Pt24 - ISO 6944

TYPICAL BASEMENT CAR PARK EXTRACT, 6 AIR CHANGES I HOUR NORMAL( 10 AIR CHANGES I HOUR SMOKE EXTRACT, RETAINING CROSS SECTIONAL

AREA OF 75% OF DUCT, 1 HOUR STABILITY AND INTEGRITYTO B.S 476 pt 24 - (ISO 6944.))THIS ALSO DEMONSTRATES COMPLIANCE WITH THE BUILDING REGULATION

REQUIREMENT OF 800 DEG C MINIMUMMELTING PO INT FOR ALL COMPONENTS


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4. REGULATIONS AND CODES

4.1 Introduction

The documents listed in this section are most of the publications relevant to theperformance requirements of ductwork in the event of a fire.

For new buildings, buildings which are changing their use, and for extensions oralterations to existing buildings, one generally should refer to the guidance given inApproved Document B, (England and Wales), Technical Standards, Parts D and E(Scotland) or Technical Booklet E (Northern Ireland).

For commercial and industrial buildings insurance may also be an importantconsideration. The Loss Prevention Council publish their recommendations in theLPC Design Guide for the Fire Protection of Buildings.

4.2 Statutory Instruments

England and Wales - Building and Buildings - The Building Regulations 1991 (SI 1991 No.

2768)Scotland - Building and Buildings - The Building Standards (Scotland) Regulations 1990 (SI1990 No. 2179 (S187))

Northern Ireland - Building Regulations (Northern Ireland) 1994 (SRNI 1994 No. 243)

4.3 Documents Supporting the Statutory Instruments

England and Wales - Approved Document B - Fire Safety

Scotland - Technical Standards, Part D: Structural fire precautions and Part E: Means ofescape from fire and facilities for fire-fighting

Northern Ireland - Technical Booklet E - Fire SafetySome Publications referenced in Supporting Documents Fire Precautions Act 1971. Guide to fire precautions in existing places of work

that require a fire certificate: Factories, offices, shops and railway premises.1989

Design principles for smoke ventilation in enclosed shopping centres.BR186,BRE,1990 (Revision of smoke control methods in enclosed shoppingcomplexes of one or more storeys. A design summary. (BRE) 1979)

Draft guide to fire precautions in existing residential care premises HomeOffice/Scottish Home and Health Dept. 1983

Firecode HTM 81 - Fire precautions in new hospitals (NHS Estates). 1996

Firecode HTM 84 - Fire safety in residential care premises (Northern Ireland).1995

Firecode HTM 85 - Fire precautions in existing hospitals (NHS Estates). 1994

Firecode HTM 86 - Fire risk assessment in hospitals (NHS Estates). 1994

Firecode HTM 88 - Guide to fire precautions in NHS housing in the community formentally handicapped (or mentally ill) people (DHSS). 1986

Firecode - Nucleus fire precautions recommendations (D of H). 1989

Building Bulletin 7 - Fire and the design of educational buildings (DES). 1988

Guide to Safety at Sports Grounds Home Office/ Scottish Office. 1990



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London District Surveyors Association

Fire Safety Guide No 1 - Fire Safety in Section 20 Buildings. 1990

Fire Safety Guide No 2 - Fire Safety in Atrium Buildings. 1989

Loss Prevention Council

LPC Design Guide for the Fire Protection of Buildings

4.4 British Standards Institution (BSI)

BS 476: Fire Tests on Building Materials and Structures

Part 4: 1970 Non-combustibility test for materials1984 Non-combustibility test for materials

Part 6: 1981 Method of test for fire propagation for products1989 Method of test for fire propagation for products

Part 7: 1971 Surface spread of flame test for materials1987 Method for classification of the surface spread of flame of products1997 Method of test to determine the classification of the surface spread

of flame of products

Part 11: 1982 Method for assessing the heat emission from building materials1988 Method for assessing the heat emission from building materials

Part 20: 1987 Method for determination of the fire resistance of Elements ofconstruction (general principles)

Part 21: 1987 Methods for determination of the fire resistance of loadbearingelements of construction

Part 22: 1987 Methods for determination of the fire resistance of non-loadbearingelements of construction

Part 23: 1987 Methods for determination of the contribution of components to thefire resistance of a structure

Part 24: 1987 Method for determination of the fire resistance of ventilation ducts(ISO 6944)

BS 5588: Fire Precautions in the Design, Construction and Use of Buildings

Part 1: 1990 Code of practice for residential buildings

Part 2: 1985 Code of practice for shops (withdrawn, now superseded by BS5588: Part 11)

Part 3: 1983 Code of practice for office buildings (withdrawn, now supersededby BS 5588: Part 11)

Part 4: 1978 Code of practice for smoke control in protected escape routesusing pressurisation

Part 5: 1991 Code of practice for fire-fighting stairs and lifts.

Part 6: 1991 Code of practice for places of assembly.

Part 8: 1988 Code of practice for means of escape for disabled people.

Part 9: 1989 Code of practice for ventilation and air conditioning ductwork.

Part 10: 1989 Code of practice for shopping complexes.Part 11 1997 Code of practice for shops, offices, industrial, storage and other

similar buildings.FR&SODUCTWORK Page 16June 2000


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BS 8313: 1989 Code of practice for accommodation of building servicesin ducts.

BS ISO 10294-1: Fire Resistance tests - Fire dampers for air distributionsystems

Part 1 1996 Test method.4.5 International Organisation of Standardisation (ISO)

ISO 834: 1975 Fire Resistance Tests - Part 1 General Requirements

ISO 6944: 1985 Fire Resistance Tests - Method for determination of the fireresistance of ventilation ducts.

4.6 Draft European Standards

prEN 1366-1 Fire resistance tests on service installations in buildings -Part 1: Fire resisting ducts

prEN 1366-2 Fire resistance tests on service installations in buildings -Part 2: Fire dampers

prEN 1366-3 Fire resistance tests on service installations in buildings -Part 3: Penetration Seals

prEN 1366-5 Fire resistance tests on service installations in buildings -Part 5: Service ducts and shafts

prEN 1366-8 Fire resistance tests on service installations in buildings -Part 8: Smoke extraction ducts

prEN 1366-9 Fire resistance tests on service installations in buildings -Part 9: Single compartment extract ducts

4.7 HVCA Documents

DW/143 A practical guide to ductwork leakage testing

DW/144 Specification for sheet metal ductwork; low medium and highpressure velocity systems (supersedes DW/142)

DW/171 Specification for kitchen ventilation systems



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Figure 9Regulations and Codes

STATUTORY INSTRUMENTSBUILDING REGULATIONS

INSURANCE REQUIREMENTS

SUPPORTINGDOCUMENTS

BRITISHSTANDARDS

ADVISORYGUIDES

ApprovedDocument B

(Englandand Wales)

TechnicalStandards

Parts D & E(Scotland)

TechnicalBooklet E(NorthernIreland)

LPC DesignGuide for the Fire

Protectionof Buildings

Codes of Practice Fire Tests

BS 8313BS 5588:Parts 1-6Parts 8-11

BS ISO 10294-1BS 476:

Parts 4, 6, 7,11Parts 20 to 24

LDSAFire SafetyGuide No 1Fire SafetyGuide No 2

Dept of HealthHTM 81HTM 84HTM 85HTM 86HTM 88



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5. STANDARD FIRE TESTS

5.1 Fire Resistance Test on Ducts

Standard fire resistance tests on ventilation ducts are carried out in accordance withBS 476: Part 24 (ISO 6944). This standard specifies a method of test and criteria forthe determination of the fire resistance of vertical and horizontal ventilation ductsunder standardised fire conditions. The general purpose of the test is to measure theability of a representative duct or duct assembly to resist the spread of fire from onecompartment to another. The test is conducted without the involvement of firedampers. It is applicable to vertical and horizontal ducts, with or without branches,taking into account joints, air supply and exhaust openings, as well as suspensiondevices and penetration seals. The performance of the duct assembly is measuredin terms of its ability to withstand exposure to high temperatures by setting criteria bywhich the resistance to collapse - ensuring the duct is able to fulfil its intendedfunction - (stability), the fire containment (integrity) and the thermal transmittance(insulation) functions can be judged. The standard temperature/time fire exposurespecified in BS 476: Part 20 is representative of only one possible fire exposurecondition at the fully developed fire stage. The method of test does not quantify thebehaviour of a duct for a precise period of time in a real fire situation but can be useddirectly to show compliance with fire resistance requirements in regulations or othersafety specifications, and enables comparisons to be made between constructions.

The specimen which is subjected to the fire test must be designed and constructed tobe representative of how it would be constructed on site. Two ducts are tested, onewith fire outside only (duct A) and one with fire on the inside (duct B). Both ductsmay be tested in either a horizontal or vertical orientation. See Figures 10 to 13.The minimum length of the specimen duct required by the test standard is 3.0m in

the furnace and 2.5m outside the furnace for horizontal ducts and 2.0m in the furnaceand 2.0m outside the furnace for vertical ducts. Horizontal duct A is fitted with abranch duct within the furnace. The recommended cross section of duct for test is1.0m x 0.25m internally. A fan is connected to the end of horizontal duct A outsidethe furnace which induces an underpressure of 300Pa inside the duct. A fan isconnected to the end of horizontal and vertical ducts B outside the furnace whichinduces air velocity of 3m/s within the ducts at ambient temperature drawn throughan opening in the side wall of the duct within the furnace. The settings of the fan arenot altered during the test. Every 30 minutes of the test the fans are switched off forfive minutes to evaluate the integrity of the ducts in the fan off situation.

The test specimen is subjected to fire on all four sides. The standardtemperature/time fire exposure is followed and the pressure in the furnace at theheight of the duct (or 100mm below the top of the furnace for vertical ducts) iscontrolled after the first five minutes of the test to be positive by 10 2Pa comparedto that of the laboratory. Thermocouples are applied to the non-fire face of the ductoutside the furnace as required by the standard and extra thermocouples areincluded within the duct to gain additional data on the fire performance. Theseadditional thermocouples enable assessments to be carried out on the duct systemwhen used as a kitchen extract duct. Observations must also be made during thetest regarding the retention of the cross-sectional area of the duct so thatassessments can be made on the duct system when used as a smoke outlet duct. A

smoke outlet duct should retain at least 75% of its cross-sectional area.The tested duct assembly is judged against three performance criteria. These are:



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Stability

Stability failure shall be deemed to have occurred in duct A within the furnaceand in ducts A and B outside the furnace when the duct collapses in such amanner that the duct no longer fulfils its intended function. Included in this isthe ability of a smoke outlet duct to retain at least 75% of its cross-sectional

area.Insulation

Insulation failure shall be deemed to have occurred when the temperature riseabove initial ambient temperature in the laboratory on the unexposed surface ofthe test specimen outside the furnace exceeds either

i) 140C as an average value; or

ii) 180C as a maximum value read by any surface thermocouple.

For kitchen extract duct A, these temperature rise limits also apply to the inside

surface of the duct within the furnace.Integrity

The presence and formation in the test specimen of cracks, holes or otheropenings outside the furnace through which flames or hot gases can pass shallconstitute integrity failure. Integrity failure shall also be deemed to haveoccurred when the cotton pad referred to in ISO 834 is ignited or whensustained flaming, of duration at least 10s, appears on the unexposed face ofthe test specimen outside the furnace.

In order to interpret the presence and formation in the test specimen of cracks,

holes or other openings outside the furnace through which flames or hot gasescan pass, the following modes of failure under the integrity criterion of BS 476:Part 20 are adopted:

Failure is deemed to occur:

i) when a 6mm diameter gap gauge can penetrate through a gap andcan be moved in the gap for a distance of at least 150mm;

ii) when a 25mm diameter gap gauge can penetrate through a gap.

Non-standard tests are carried out to the principles of BS 476: Part 24, but atreduced furnace temperatures, for applications such as smoke extraction systems

where the maximum exhaust temperatures are specified and the ductwork does notpenetrate fire separating elements. The results from similar tests can also be utilisedfor installations where a fire engineering analysis has been carried out on the buildingand the maximum temperature to which the duct would be exposed in a fire situationhas been calculated. An example of such an installation is in an atrium of a multi-storey building where the ducts are designed to extract smoke and hot gases in theevent of a fire and to prevent flash-over occurring.

BS 7346: Part 2 describes the classification and method of test for poweredventilators (not ductwork) designed to remove hot gases and smoke from buildings inthe event of fire. The standard is primarily concerned with the evaluation of ventilatorperformance at elevated temperatures.



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5.2 Reaction to Fire Tests

In order to restrict the use of materials in the construction of buildings which igniteeasily, which have a high rate of heat release and/or which reduce the time to flash-over, reaction to fire tests are carried out on component materials and linings ofducts. These are carried out to show compliance with reaction to fire requirements in

regulations or other specifications. The tests which are used to demonstratecompliance are:

Method of test to determine the classification of the surface spread of flame ofproducts - BS 476: Part 7. This test measures the rate at which flame is able tospread over the surface of a lining material. The material or product isclassified 1,2,3 or 4 with Class 1 being the highest classification (least flamespread).

Method of test for fire propagation for products - BS 476: Part 6. This testmeasures the rate of heat release from a product or material. From this test,indices of performance are calculated. Index of performance (I) relates to the

overall test performance, whereas sub-index (i 1) is derived from the first threeminutes of test. The maximum acceptable fire propagation indices arespecified in the various regulations.

Method for assessing the heat emission from building materials - BS 476: Part11, and Non-combustibility test for materials - BS 476: Part 4. These two testsare similar and are used to determine the heat emission from a product ormaterial. Materials of limited combustibility are defined in the national BuildingRegulations by reference to the method of test specified in Part 11. Non-combustible materials are also defined in the national Building Regulationseither as listed products or in terms of performance when tested to Part 4 or

Part 11. Non-combustible materials may be used whenever there is arequirement for materials of limited combustibility.

An additional product performance classification for lining materials defined in thenational Building Regulations is Class 0. This is achieved if a material or the surfaceof a composite product is either:

i) composed throughout of materials of limited combustibility, or

ii) a Class 1 material which has a fire propagation index (I) of not morethan 12 and sub index (i 1) of not more than 6.

Class 0 is not a classification identified in any British Standard test.

NOTE: The fire resistance tests and reaction to fire tests described above are thecurrent UK national standards and reflect the requirements of the various UK nationalbuilding regulations or other safety specifications. Work is proceeding within CEN todevelop European Standards for fire resistance tests on ducts and reaction to firetests. However, at the time of writing, these standards have only been published indraft form.



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Figure 10: Test arrangement for vertical ductsTypical test arrangement to BS 476: part 24: 1987


Section Dimensions in miHimetres

Sealed end

Duct B

Opening . . . - - - - - T - - 1 ~ - J o i n t s

Duct A

N

Fumace roof A

Joints - - f " t - - - - . . . . N~ 5 0 0 A

/ / /

Sealed e n d - ' - - - - - - - - . /

Measurement of elongation or shortening

A-A

1::.::..::::.:::::::::1 ~ : : : : : : : : : : : : 1 - l n s u l a t i o n

Alternative arrangement for assemblies of ducts

t::::;:::::::::,:::J:::::::;:::::::::J


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Figure 11: Test arrangement for horizontal ductsTypical test arrangement to BS 476: part 24: 1987


Plan

Duct A

Duct B

> 2 500

NOTE: The sealed end shall be independent of the furnace wall

Joints

2000

Fire-stoppingas in practice

Insulation

:>2 500

Fire-stopping as in practice

Joint

2000

;;;..2500

Dimensions in millimet res

Rigid restraint, ifapplicable


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Figure 13Location of thermocouples on horizontal ducts outside the furnace

Typical test arrangement to BS 476: part 24: 1987


Plan

~ : ::.::::.::: .1>