FOR THE DESIGN OF SMOKE VENTILATION SYSTEMS FOR SINGLE STOREY INDUSTRIAL BUILDINGS, INCLUDING THOSE WITH MEZZANINE FLOORS, AND HIGH RACKED STORAGE WAREHOUSES

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GUIDANCE FOR THE DESIGN OF

SMOKE VENTILATION SYSTEMS FOR

SINGLE STOREY INDUSTRIAL BUILDINGS,

INCLUDING THOSE WITH MEZZANINE FLOORS,

AND HIGH RACKED STORAGE WAREHOUSES

produced by

SMOKE VENTILATION ASSOCIATION

of HEVAC Manufacturers

Issue 3

Published by the Federation of Environmental Trade Associations

All rights reserved. No part of this publication may be

reproduced, stored in a retrieval system, or transmitted in any

form or by any means, electronic, mechanical, photo-copying,

recording or otherwise, without the prior permission of the

Federation of Environmental Trade Associations, Sterling House,

6 Furlong Road, Bourne End, Bucks, SLS 5DG.

CONTENTS

PAGE

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FOREWORD 1

1 SCOPE 1

2 DEFINITIONS 1

3 DESIGN PARAMETERS 3

4 FIRE SIZE 4

4.1 INDUSTRIAIL BUILDINGS -

(EXCLUDING HIGH RACKED STORAGE WAREHOUSES) 4

4.2 HIGH RACKED STORAGE WAREHOUSES 6

5 TOTAL HEAT OUTPUT OF FIRES 6

6 CONVECTIVE HEAT OUTPUT 8

7 CLEAR LAYER 8

7.1 INDUSTRIAL BUILDINGS -

(EXCLUDING HIGH RACKED WAREHOUSES) 8

7.2 HIGH RACKED STORAGE WAREHOUSES 9

8 SMOKE COMPARTMENT 12

8.1 BUILDINGS WITHOUT MEZZANINE FLOORS 12

8.2 BUILDINGS WITH MEZZANINE FLOORS 12

9 SPRINKLERS 13

9.1 INDUSTRIAL BUILDINGS -

(EXCLUDING HIGH RACKED STORAGE WAREHOUSES) 13

9.2 HIGH RACKED STORAGE WAREHOUSES 13

9.2.1 CEILING LEVEL SPRINKLERS 14

9.2.2 ESFR SPRINKLERS 14

9.2.3 IN-RACK SPRINKLERS 15

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PAGE

10 DEPTH OF SMOKE LAYER 17

10.1 INDUSTRIAL BUILDINGS -

(EXCLUDING HIGH RACKED STORAGE WAREHOUSES) 17

10.2 HIGH RACKED STORAGE WAREHOUSES 17

11 AMBIENT TEMPERATURE l8

12 AIR INLETS/REPLACEMENT AIR l8

13 WIND EFFECTS l8

14 SPECULATIVE BUILDINGS l8

15 SIZING/SITING OF EQUIPMENT 20

16 CONTROLS 20

17 MEZZANINE FLOORS 21

17.1 CLEAR LAYER 21

17.2 PERMEABLE MEZZANINE FLOORS 22

17.3 SOLID (NON-PERMEABLE) MEZZANINE FLOORS 22

APPENDIX 1 - ASSOCIATED BRITISH STANDARDS 27

APPENDIX 2 - REFERENCES 28

APPENDIX 3 - CLASSIFICATION OF SPRINKLER CATEGORIES

FOR INDUSTRIAL BUILDINGS 30

APPENDIX 4 - RATES OF HEAT RELEASE FOR VARIOUS FUELS 33

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FOREWORD

The use of smoke and heat exhaust ventilators has been

widespread and their value in assisting in the evacuation

of people from buildings, reducing fire damage and financial

loss by preventing smoke logging, facilitating fire fighting,

reducing roof temperatures and retarding the lateral spread

of fire is firmly established. Therefore, it is essential

that the purpose of the scheme is identified.

The members of the Smoke Ventilation Association have had

many years of interpreting and applying the various design

principles included in the many publications dealing with

smoke control. Based on this experience, the Guide sets out

their recommendations for design considerations. Actual

methods of calculation are set out in various Fire Research

Station (FRS) papers, which are referred to in the text and

listed in Appendix 2.

No scheme will work satisfactorily unless it is correctly

installed and maintained.

1 SCOPE

This guide covers Single Storev Industrial Buildings such as

Factories and Warehouses, including such buildings which

contain Mezzanine Floors, and High Racked Storage Warehouses.

2 DEFINITIONS (see Appendix 1 Reference 1)

DESIGN FIRE SIZE The base dimensions of the largest fire

with which a smoke ventilation system

should be expected to cope. A Design Fire

is normally taken to be square or

circular.

HEAT OUTPUT The total heat generated by the fire

source, including that which may appear

at any point downstream (see also 2.7).

CLEAR LAYER The vertical distance between floor level

and the bottom of the smoke layer.

SMOKE Region of ceiling or roof void isolated

COMPARTMENT from other areas, by building structures

and/or purpose made screens designed to

to prevent the flow of smoke from the

compartment.

SMOKE LAYER The vertical distance from the "centroid"

DEPTH of the extractor (whether horizontal or

vertical plane) to the bottom of the

smoke layer.

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REPLACEMENT AIR Cool, ambient temperature, smoke free air

entering the Smoke Compartment during

course of operation of Smoke Ventilation

System to replace the exhausted hot

smoke.

HEAT FLUX The total heat energy carried by the

gases across a specified boundary. This

flux can be convective, radiative and/or

conductive, or a combination thereof.

There is a further form, often referred

to as a "potential" heat flux. This may

be defined as the flow across a specified

boundary of energy yet to be converted to

heat by the fire process.

HEAT LOSS The total heat transferred away from

a body (including gas) through its

boundaries by convection, radiation

and/or conduction, or a combination

thereof, eg heat loss from a gas layer

can be by radiation, convection and

conduction to its surroundings.

CONVECTIVE HEAT That portion of the total heat output

FLUX retained within the flowing gases

immediately outside the combustion

region. This heat flux is, of course,

subject to consequent heat loss.

SMOKE CURTAINS (See Appendix 1 Reference 2)

/SCREENS These are employed as part of a smoke

control system to create ceiling

reservoirs from which smoke and hot

gases can be extracted.

AERODYNAMIC The "Measured Free Area" of the natural

FREE AREA heat and smoke exhaust ventilator

multiplied by the "Coefficient of

Discharge".

MEASURED FREE The actual measured throat area of the

natural heat and smoke exhaust

ventilator: This is the smallest clear

opening normally between the drainage

channels. No reduction should be made

for controls,1ouvres and/or other

obstructions, providing their obstruction

is allowed for in the coefficient of

discharge.

COEFFICIENT OF The ratio of Actual Flow Rate to

DISCHARGE Theoretical Flow Rate through a natural

heat and smoke exhaust ventilator.

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CONVECTIVE HEAT Heat content of smoke, calculated as

OUTPUT convective heat flux for a design fire

minus subsequent heat losses. Normally

considered as the value to be used

fordesign purposes.

MEZZANINE An intermediate floor level between the

ground floor level and the roof space of

a single storey industrial building. this

mezzanine floor level to be open to the

remainder of the building so that smoke

will pass freely from one area to the

other and thereby hamper the safe

evacuation of the occupants of the upper

levels in a fire.

HEIGHT OF The vertical distance from the floor

MEZZANINE to the underside of the lowest solid

mezzanine floor level.

PERMEABLE A mezzanine floor which has at least 25%

MEZZANINE of its total plan area evenly distributed

FLOORS as free area for the passage of smoke.

SOLID MEZZANINE A mezzanine floor which is either solid

FLOOR or does not meet the criteria for an

open mezzanine floor.

FLASHOVER A condition when the temperature of the

gases contained in the smoke layer is

sufficiently high to cause spontaneous

ignition (generally due to downward

radiation of heat) of materials not

directly involved in the fire. This

condition should be avoided for obvious

reasons. It is normally considered to be

when the smoky gas layer temperature is

in the region of 500 - 600 degrees

centigrade.

CEILING JET A horizontally flowing layer of hot gases

driven in part by the kinetic energy of

the initially vertically rising fire

plume. It typically has a depth of

approximately 1/lOth of the building

height flowing radially away from the

plume axis.

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3 DESIGN PARAMETERS

Fire Size

Heat Output of Fire (convective) Clear Layer

Smoke Compartments

The Effect of Sprinklers

Depth of Smoke Layer

Ambient Temperature

Air Inlets/Replacement Air Wind Effects

Speculative Buildings Sizing/Siting of Equipment Controls

Mezzanine Floors

4 FIRE SIZE

4.1 Industrial Buildings

(Excluding High Racked Storage Warehouses)

4.1.1 Calculations should be based on a steady state

fire condition.

4.1.2 No scheme should be designed on a fire size of less

than 3m x 3m, unless there is a known or isolated

fire risk whose size is known, ie Quench Tank,

Spray Booth etc.

4.1.3 It is recommended that for sprinklered buildings

one of the following steady state fire sizes in

Table 1 is used.

TABLE 1 - STEADY STATE FIRE SIZES

Hazard Fire Size Perimeter Approx Examples of

Category Area Occupancy

(m²) (see also

Appendix 3)

Group 1 3.0 x 3.0m 12m 9 Breweries

Group 2 4.5 x 4.5m 18m 20 Bakeries

Group 3 6.0 x 6.0m 24m 36 Cotton Mills

Group 4 9.0 x 9.0m 36m 81 Paint Manuf’ring

Group 5/1 3.0 x 3.0m 12m 9 Electrical W’house

Group 5/2 4.5 x 4.5m 18m 20 Pharmaceutical W’hse

Group 5/3 6.0 x 6.0m 24m 36 Paper Storage W’hse

Group 5/4 9.0 x 9.0m 36m 81 Plastic Foam W’house

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In unsprinklered premises there is the possibility that, in

the absence of effective suppression (eg. sprinklers), the

fire may grow unchecked and eventually destroy the building.

In this instance the detection of the fire is paramount, and

human detection should not be relied upon. Hence a fire/smoke

detection system is recommended to:

(a) raise the alarm both within the building and with the

fire brigade;

(b) initiate the operation of the venting system

The fire may then develop if unchecked to a size at fire

service intervention which will be dependent upon:

(i) the nature of the goods, ie.

combustibility, burning.rate, radiation

output, etc;

(ii) the disposition of the burning material

with respect to other combustibles;

(iii) the geometry of the building

(eg. ceiling height etc);

(iv) the attendance and deployment time of the

fire service

An assessment of the largest likely fire size that the fire

service will encounter should be based upon the above

variables. In the absence of sufficient information or other

guidance being available (eg. British Standards), it is

suggested that the fire size for an unsprinklered fire be

taken as being twice the area of its sprinklered counterpart,

eg. a fire in a Group 3 hazard should be taken as 70m² area

(8.5m x 8.5m). An upper limit of around l00m² (lOm x lOm) may

be considered as an arbitrary maximum beyond which the venting

system will produce no further tangible benefit, other than to

assist fire-fighting operations.

Fire sizes outside these are not normally considered, and in no

circumstances should the design fire size for an unsprinklered

fire be less than that for a sprinklered fire of the same

hazard rating.

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4.2 High Racked Storage Warehouses

4.2.1 The potential for fire growth needs to be fully

considered since it is much greater within racked

goods than with materials stored only at ground

level.

Thus for high racked storage systems that do not

employ in-rack or ESFR sprinkler systems the

assumed minimum fire size should not be less than

3m x 3m, and this minimum size should only be

considered in exceptional circumstances.

4.2.2 The nature of the stored goods is vital in the

consideration of the fire size.

4.2.3 The type of packaging material must be

considered in the assessment of the fire size.

4.2.4 The manner of the storage wil1 affect the

potential fire size. For example, paper rolls

stored upright', ie with the hole in the centre

vertical, will allow the fire to grow much faster

than if the paper is stored horizontally.

4.2.5 The surface area of material which can support

combustion must be considered.

4.2.6 The type of sprinkler system to be installed will

affect the fire size selected. See clause 9.

5 TOTAL HEAT OUTPUT OF FIRES

5.1 Figures for the heat release rate (RHR) of known fuel

combinations were compiled for various storage and

process risks in industrial buildings by the Fire

Research Station (see Appendix 2, Reference 1), but

Were categorised in a way unhelpful to smoke control

designers. These data were later revised to provide the

necessary basis for smoke control design (see Appendix 2,

Reference 2). The National Fire Prevention Association

(NFPA) of America have similarly compiled RHRs for

various fuels following experiments (see Appendix 2,

Reference 3). Further data for specific fuels have also

been compiled by the FRS (see Appendix 2, Reference 4).

Appendix 4, Tables A4.1-A4.3 list the various fuels and

fuel arrays, from both UK and USA references.

5.2 For storage risks there is a wide range of values of RHR

for essentially very similar storage categories, eg.

goods stacked in cardboard cartons.

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TO BE EDITED

It is a fundamental principle of smoke ventilation that the RHR

chosen for the design fire will affect the calculated

ventilation area or rate of exhaust. Storage risks may also

vary from the initially chosen fuel, eg. glassware in cardboard

cartons to plastic components in cardboard cartons. The nature

of the occupancy (risk) will not have changed (ie. storage),

but the potential RHR will, perhaps reducing the value of the

smoke control system. This can, to a certain extent, be

alleviated by designing the system to deal with the worst-case

scenario for the risk. Table 2 provides the data in Table A4.1

(storage risks) in terms of upper and lower limits for the

various storage categories. The values provided are RHR per

square metre (plan area) for each metre height of storage.

TABLE 2 RATES OF HEAT RELEASE FOR VARIOUS STORAGE CATEGORIES,

PER METRE HEIGHT OF FUEL

Range of RHR

Storage

(kW/m²/m)

Loose wood & wood products,

Inc. wood cribs & pallets;

Upright wood storage. 1800 - 2900

Stacked wood & wood products,

Inc. furniture; books;

Crated objects. 30 - 720

Cardboard & paper products,

Inc. stacked or loose

cardboard boxes or cartons

which are empty; cardboard

tubes or reels; mailbags, 120 - 240

Any storage in cardboard boxes

or cartons*. 160 - 1200

Loose or stacked plastic

prodcuts, inc. PP & PE films

in rolls; PU & PS Insulation

Boards; PE Trays. 260 - 1280

* NB Excludes the apparently anomalously high values for

PS jars in cartons.

The total heat output is calculated from the product of the

plan area of the fire, its height and the appropriate RHR

values.

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5.3 Where information on the exact nature of the fuel

Is unknown, eg. speculative buildings, and the local

regulatory authorities have not recommended the design

fire size and RHR, then a range of RHR of 60-500kW/m²/m

is recommended, with a minimum ·assumed storage height of

2m (see Appendix 2, Reference 5). Further design details

for speculative buildings may be found in Section 14.

5.4 The designer should use both values of RHR from Table 2

for the particular occupancy examined, or as in 5.3 above

for speculative buildings, and calculations performed to

determine all of the necessary design parameters. From

these two sets of results, the worst case parameters

resulting from either value of total heat output should

then be used in the design.

5.5 For specific non-storage occupancy or liquid fuel risks,

then the RHRs in Tables A4.2 and A4.3 should be used to

determine the total heat output.

6 CONVECTIVE HEAT OUTPUT

When heat is given off some of it is lost to the structure

and contents by radiation from the hot gas plume. If the roof

reservoir compartments exceed 2000m² in plan area then

consideration should also be given to the radiative and

conductive losses from the established smoke layer to the

roof structure (see Appendix 2 Reference 6).

The convective heat output of the fire is determined by

applying a correction factor to the total heat output

(see Section 5).

Various technical papers give differing values for the heat

loss correction factor. Further research is desirable but, in

the meantime, a 20 percent loss should be applied. For roof

areas greater than the recommended smoke compartment size,

calculations of the heat lost from the smoke layer should be

provided to support the increase in recommended reservoir

size such as a Newtonian heat transfer coefficient method

(see Appendix 2 Reference 7).

7 CLEAR LAYER

7.1 Industrial Buildings excluding High Racked Warehouses

7.1.1 The minimum clear layer should be 3.0m. This is

to permit the escape of personnel and the entry

of fire fighters. Note, however, that the

maximum clear height which car be physically

achieved is 80-90o of the building's height,

due to the presence of the ceiling jet in the

smoke layer (see Appendix 2 Reference 7).

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7.1.2 Where the chances of spontaneous ignition and

flashover present a considered risk, and the

maximum clear height available permits it, the

clear layer should extend at least SOOmm above

the stacked goods.

7.1.3 To avoid disruption of the smoke layer in any

single compartment, the base of the smoke layer

should be at least 1-2m above any door/opening

which might either by design or chance be a

source for replacement air, unless the incoming

air velocity is less than lm/s, in which

instance it should be no less than SOOmm above

the opening.

7.1.4 Where the floor level changes within a

compartment, the height of rise should be

measured from the shallowest end for safety

purposes and the overall height from the

deepest end for the entrainment calculation.

7.1.5 Special considerations are necessary when

designing for-mezzanine floors. Note the

comments contained within the Design Parameters

for Mezzanine Floors.

7.2 High Racked Storage Warehouses

7.2.1 In sprinklered warehouses, the system

objectives must be clearly defined for a design

to be produced. These objectives may be to.

(a) Protect personnel within the building, by

ensuring that their escape routes remain

unaffected by smoke;

(b) Protect stock and materials which may be

combustible or salvageable;

(c) Facilitate fire-fighting operations.

7.2.2 For objective (a) to be achieved the design

approach can be either 7.2.2.1 and 7.2.2.3 or

7.2.2.2 and 7.2.2.3.

7.2.2.1 (1) Ensure that the smoke layer is is

established well above head height

ie >lOm above the floor or highest

exposed walkway (other than those used

for infrequent maintenance purposes).

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(ii) Provide no reservoir compartment sub-

divisions but ensure that the additional

heat losses from the smoke layer due to

the extended layer area are accounted

for, using a calculation technique which

takes into account convective and

radiative heat transfer from the layer

to the buildings fabric and atmosphere.

The final smoke layer temperature should

o

not be less than 20 C above the average

roof level ambient temperature.

The relaxation on compartmentation is

based on the assumption that escaping

personnel will be able to travel hrough,

and out of, the building without being

detrimentally affected (psychologically)

by the presence of the smoke layer above

their heads, by virtue of its height

above the floor and the nature of their

escape routine, (ie regimented and

practiced escape drill).

(iii) Ensure that an adequate fail-safe low

level inlet air supply is available at

all times, except where reservoir sub-

division are used for this purpose (see

clause 12). Note. It should be

remembered that low level doors/windows

may be secured and low level inlets may

be partially blocked by stored materials.

7.2.2.2 (i) Where it is desirable for the smoke

layer to descend below lOm above the

floor, then the minimum height of rise

should be 3m, and screen separation of

the roof space into reservoirs not

exceeding 60m in the direction of escape

is required. Note, if the plan area of

the reservoirs is greater than 2000m²,

consideration should be given to the

heat losses sustained by the layer.

(ii) In exceptional circumstances it may be

impractical to install such screens. In

these instances alternative smoke ontrol

solutions may be considered, and etailed

calculations shall be provided in

support of any alternative strategy.

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7.2.2.3 All life safety systems should operate on

smoke detection and where possible sprinkler

flow switch.

7.2.3 For objective (b) to be achieved the design

approach can be.

(i) Ensure that the design smoke layer is

established above the salvageable stock

levels (except in the instance where this

will result in a smoke layer depth less

than 1/lOth the building height,

see 7.2.5 below).

(ii) Provide screen separation of the roof

space into reservoirs not exceeding

3000m². Where for practical purposes it

is desirable to exceed this area, the

heat losses from the layer should be

taken into account (see 7.2.2.1 (ii)

above). The final design smoke layer

temperature should not be less than 20C

above the average roof level temperature.

(iii) The inlet air supply may be provided from

adjacent, unused reservoirs, or dedicated

low-level openings.

(iv) The venting system should preferably be

operated by a smoke detection system, but

as a minimum should operate on sprinkler

flow switch for in-rack sprinklers, smoke

detectors for roof mounted sprinklers or

on both.

7.2.4 For objective (c) to be achieved the design

approach can be as per objective (a) (see 7.2.2

above), with the exception that smoke reservoir

screens will not be required except to provide

inlet air, and the system may be operated by

sprinkler flow switch and manually by fire-

fighters.

7.2.5 The minimum layer depth used in a design cannot

be less than l0% of the building (room) height,

due to the presence of the ceiling jet in the

smoke layer (see Appendix 2 Reference 7).

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7.2.6 Where the floor level changes within a

compartment, the height of rise should be

measured from the shallowest end for safety

purposes and the overall height from the

deepest end for the calculation.

7.2.7 In unsprinklered warehouses, the current fire

experience has been the total involvement, and

subsequent loss, of the building. The speed of

fire growth in all but the least combustible of

materials (eg. steel) is such that venting is

ineffective for practical considerations of

stock protection and fire-fighting operations.

See 9.2 below.

8 SMOKE COMPARTMENT

8.1 Buildings without Mezzanine Floors

8.1.2 Where required smoke compartments should have

a maximum area of 2000m² for life safety

purposes to 3000m² for other purposes with the

latter used only in exceptional circumstances

(see Appendix 2 Reference 8).

8.1.2 When used for personnel protection the maximum

length of any side of a smoke compartment in the

direction of escape should be 60.0m

(see Appendix 2 Reference 6).

8.1.3 Smoke curtains should terminate 500mm below the

design smoke layer base.

8.2 Buildings with Mezzanine Floors

8.2.1 Where reservoir limitations are required below

the mezzanine as part of the design, the

parameters given in 8.1 above should be applied.

When the design philosophy applied is to allow

the smoke to spill into an adjoining area, care

must be taken not to exceed the total reservoir

size of 2000 to 3000m² maximum.

The size of the reservoir is the combined total

of the under mezzanine floor smoke control zone

plus the area of the smoke control zone into

which the smoke is designed to flow.

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9 SPRINKLERS

9.1 Industrial Buildings Excluding High Racked Storage

Warehouses

Whilst it is generally agreed that the operation of

sprinklers will reduce the fire size and the amount

of heat released, current research shows that where

sprinklers and smoke vents are installed, the operation

of the ventilators in any one compartment does not

delay significantly the activation of sprinklers

(see Appendix 2 References 7 and 9).

The effect of the sprinklers on the temperature and

buoyancy of the smoke must be allowed for in the design

of the smoke extraction system, as the smoke may have

to pass through several rings of sprinklers before

being exhausted (see Appendix 2 Reference 10).

The designer should specify the allowances made for

sprinklers in the calculations.

9.2 High Racked Storage Warehouses

Unsprinklered high racked storage buildings have been

commonplace, but due to the fire experience in such

environments are now becoming less freguent. However,

if a design is required for such a building the fire

risk will be substantial, and experience has shown that

smoke ventilation has provided very limited additional

escape time, sufficient to save lives, but cannot be

depended upon to aid the fire brigade in fighting the

fire. Flashover in these circumstances is almost

certain to occur. The smoke ventilation system designer

should strenuously recommend the installation of a

sprinkler system.

The effect of sprinklers in a high bay warehouse has to

be considered in more detail than in other situations.

The type of sprinkler heads must be considered, eg.

Early suppression fast response ceiling mounted (ESFR)

Ordinary response ceiling mounted

Ordinary response in-rack

Fast response in-rack

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The operating temperature of such heads must be

considered. Typical temperatures are.

68 degrees centigrade

93 degrees centigrade

141 degrees centigrade

The spacing of the sprinkler heads, eg.

Every storage level

Alternative storage levels

Roof level only

A combination of any of the above

Al1 of the above are alternatives and will affect the

design fire size. The designer should state within his

calculations what assumptions have been made.

9.2.1 Ceiling Level Sprinklers

Ordinary Response

With ordinary response ceiling mounted sprinklers

only, the water sprays will find it difficult to

penetrate into the middle of the racks.

Extinguishment will depend on water trickling

into the main seats of fire, with the consequence

that higher water flow rates will be needed.

Fire can be expected to "burrow" through shielded

areas of fuel until it reaches parts where

sprinklers are not yet wetting,the racks. At this

point the fire will flare up and set off more

sprinklers.

This behaviour was observed in some of LPC's

High-Piled palletted fires for the CEA. The

design fire size will be as hazard category 5

of Table 1 (see Section 4).

9.2.2 ESFR Sprinklers

Research carried out by others has indicated that

ESFR sprinklers appear to provide the best means

of control for a ceiling mounted system, for

buildings up to 12m in height. At or below this

height the design of the smoke control system can

be treated as for an in-rack sprinkler system.

There appears to be no research on the efficiency

of these systems above this height.

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It therefore seems reasonable to treat the

sprinklers as being more effective than ordinary-

response ceiling mounted systems, but less

effective than in-rack systems. In which instance

the design fire size adopted may be taken as a

mean value between the two.

The heat flux generated by the fire becomes less

important, as the effect of the sprinklers will

be to reduce the smoke layer temperature, and in

turn the smoky gas buoyancy. This must be

considered when natural ventilators are to be

installed, and the smoke layer temperature rise

above ambient should be limited to the minimum

sprinkler operating temperature minus ambient air

temperature. When mechanical ventilators are to

be used, it is recommended that a maximum of 50o

of this cooling should be considered. (This is

the average of the maximum calculated temperature

plus the sprinkler operating temperature).

The designer must state the degree of cooling

caused by the sprinklers which has been allowed

for in the calculations. Where there are extended

reservoir sizes (or no reservoir at all)

calculations of the additional heat lost from the

layer beyond the zone of sprinkler activity must

be stated.

9.2.3 In-Rack Sprinklers

Where there are sprinklers mounted in-rack, the

flame front rising up the rack may pass some

sprinkler heads before they operate. This effect

is particularly marked for face ignition. This

could lead to a fire which may be controlled, but

not extinguished, by the sprinklers when they do

operate, and the fire is likely to continue

burning.

In high racked fires the rising gases become

"channelled" by the flues formed by the racks.

The fire plume effectively has vertical sides

corresponding to the flues. The pattern of smoke

movement may be complicated by some smoke

spreading horizontally beneath shelves, but the

plume will rarely spread beyond a 2 bay width. It

does not spread at an angle of 15 degrees from

the vertical as is assumed for most axisymmetric

plumes in single storey buildings.

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Heat may be generated through a significant

height of the rack, even when the fire is being

controlled by the sprinklers. This suggests a

useful analogy with the "Thomas" large-fire

plume, since its original derivation was for

those parts of a flame plume where combustion was

taking place in the gas phase, ie heat was being

generated throughout the height of plume. This

has the advantage that the large fire entrainment

model for a single storey building may be used.

The height of rise used should be taken as the

height from the lowest possible seat of fire (ie

usually the floor) to the base of the smoke

layer, and the perimeter of the fire must be that

part of the fire open to the air being entrained.

In practice this means that where the fire is in

the middle of a long rack, the only contribution

to the perimeter will come from the front 'face

of the rack (or if the fire is able to burn

through to both faces, from both front and back

faces of the rack). The lateral extent of fire

spread is less easy to assess, but should be

assumed to be the lateral separation between

sprinkler heads or two bay widths, whichever is

less - in most instances around 3m.

The fire 'size should therefore be taken as

either.

(a) One side of rack affected only

(b) Both sides of rack affected

The perimeter described by (b) should be used in

all cases. The only exceptions are when there is

a physical separation between the two faces of a

rack or when fast-response in-rack sprinklers are

installed to the precise specification and within

the limitations (experimental) laid down by the

FRS (Appendix 2 References 11-14) in these cases

perimeter (a) can be used.

During in-rack sprinkler tests at Cardington,

casual observation by FRS staff of the amount of

shimmer at a metre or two above the top of the

12m test rack suggested a gas temperature of

200C ± 50C when sprinklers were operating in-

rack. This estimate was unfortunately not

supported by any instrumentation at the time,

since it lay outside the design objectives of the

particular experiments. It is hoped that further

research will yield better data.

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There is no indication that fire will progress

further up the racks, hence this value can be

taken as a limiting parameter, with the heat flux

being generated over a 12-14m height. Using the

previously described values of fire perimeter,

and the mass flow equation, the convective heat

flux generated can be approximated.

Where ceiling sprinklers are installed, either

complementary to, or in replacement of the

topmost in-rack sprinkler level, the final gas

layer temperature must be limited as described in

9.2.1 above, prior to further calculation of any

losses due to extended reservoir sizes.

10 DEPTH OF SMOKE LAYER

10.1 Industrial Buildings Excluding High Racked Storage

Warehouses

In order to avoid the risk of "flashover", sufficient

ventilation should be provided to ensure the smoke

layer temperature does not exceed 600C for the design

conditions (see Appendix 2 Reference 2). However, the

smoke layer depth cannot be less than 10% of the

building (room) height. Where this occurs

consideration should be given to other (additional)

forms of protection, eg sprinklers.

10.2 High Racked Storage Warehouses

10.2.1 Since it is extremely unlikely for an

unsprinklered high racked storage area to

survive a fire, the following applies to areas

which are sprinklered, where flashover is not

likely to occur. However, flashover should

alvaays be considered, as this guide

recommends.

As the smoke layer base will be in many

instances, by design, at a high level within

the building, it is likely that cool smoke

temperatures will result, especially if

extended reservoirs are employed.

Smoke temperatures less than approximately 20

degrees centigrade above the average roof level

ambient temperature have resulted in the smoke

layer de-stratifying and mixing downward with

the ambient air beneath. This is mainly due to

weak cross-draughts and convection currents,

and will occur despite the provision of a smoke

extraction system. This scenario must be

considered by the designer.

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10.2.3 The cooling effect of the operation of the

sprinklers must be considered, refer to

9.2 above.

The designer must state the degree'of cooling caused

by the sprinklers and extended layer travel which has

been allowed for in the calculations.

11 AMBIENT TEMPERATURE

o

For smoke venting calculations a figure of 288 K should be

used (see Appendix 2 Reference 8).

12 AIR INLETS/REPLACEMENT AIR

12.1 For any scheme to be effective, sufficient replacement

air must be provided in order that extract ventilators

operate properly (see Appendix 2 Reference 6).

12.2 Doors and windows, as well as ventilators, can be used

for replacement air. However, if intended for use in

this way the'y should be fitted with automatic

controls compatible with the system. The designer

should state the ratio of extract to inlet area used

in his calculations.

12.3 To avoid disruption of the smoke layer in any single

compartment, the base of the smoke layer should be at

least 1-2m above any door/opening which might either

by design or chance be a source for replacement air,

unless the incoming air velocity is less than lm/s, in

which instance it should be no less than 500mm above

the opening.

12.4 The design inlet velocity shall not exceed 5.0m/s.

12.5 Ideally, replacement air should be introduced at

low level from all directions. However, natural

ventilators in the non-fire compartments can be used

if smoke curtains/screens are fitted to prevent short

circuiting.

12.6 Powered ventilators can be used for replacement air.

Care should be taken as they may cause turbulence

which can increase smoke/fire spread.

12.7 Where security bars, "insect" mesh or bird screens are

fitted, the effect of these should be considered when

determining the ventilator discharge coefficient.

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13 WIND EFFECTS

The designer should consider the effect of wind pressures

on smoke extraction systems.

Information published by the Building Research

Establishment and BSI (CP3, chapter V pt 2) shows for a

building considered in isolation, natural ventilators will

o

be subject to negative pressure of roof slopes of 30 , or

less, from the horizontal.

Installations of natural ventilators on roofs over 30 from

the horizontal should not be considered without some form

of baffling unless supporting data from wind tunnel tests

and/or computer simulation is available. This baffling can

be external to the unit or part of the ventilator design.

When changing wind directions may cause positive or

negative pressure fluctuation in the building structure,

natural extract ventilators should be installed in

sufficient numbers and positions and controlled via wind

sensor/pressure monitors to ensure that an appropriate

number open at any one time.

If in doubt about pressure distribution on the building

structure, a powered system should be used.

Snow loadings should also be considered when designing/

siting of both powered and natural supply/extract systems.

Any effects caused by the wind which may affect the smoke

ventilation system proposed, must be clearly stated by the

designer.

14 SPECULATIVE BUILDINGS

This is not, relevant to Mezzanine Floors or High Racked

Storage Areas since it is extremely unlikely that such a

building would be built speculatively.

Where designers are called upon to design systems for

buildings where details of the occupancy, use, sprinklers

etc. are unavailable, the following minimum criteria should

be used for design.

14.1 4.5m x 4.5m sprinklered fire (see Sections 5.3 and

5.4 for heat output).

14.2 Clear layer to eaves level or 500mm above the top of

the highest opening.

14.3 Replacement air not available from doors and windows.

14.4 Smoke compartments to be limited to 2000m² max.

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15 SIZING / SITING OF EQUIPMENT

All smoke control products should comply with the

requirements of the "SVA Guide to good practice on

application of smoke control equipment and systems" (see

Appendix 2, Reference 15). Extract equipment should

not exhaust at a rate likely to puncture the smoke layer

and should be sited in such a way as to not disturb the

smoke layer base. Particular consideration should be given

to High Racked Storage Areas since the smoke layer depth

is freguently very shallow in these buildings. (In this

context) mass flow rate and velocity should be considered

(see Appendix 2 References 16 and 17).

Rules used in the Industry are:

15.1 The size of natural and powered extract units should

be limited to prevent puncture of the smoke layer.

Reference 16, Appendix 2 shows methods of calculation

and limiting factors.

15.2 Natural extract ventilators should not be spaced

morethan 20m apart.

15.3 For natural systems, the preferred aerodynamic area

Of inlet should be at least equal to the aerodynamic

areaof extract. The designer should state the actual

ratio taken into account in calculations.

15.4 For mechanical systems, inlet resistance should be

considered when sizing equipment extraction and the

value should be stated by the designer.

15.5 Fan motors should be rated at temperatures compatible

with the system design, but should be sized to

operate at ambient conditions (288K).

15.6 Compressed air receivers should be capable of three

operations of the system after power failure.

15.7 Exhaust equipment should meet the specifications of

the relevant British Standard (see Appendix l,

References 3 and 4).

16 CONTROLS

Controls form an integral part of the system design.

16.1 A smoke extract system is operated by an automatic

control system, which may be activated by any of the

following:

Smoke detection; heat detection; sprinkler flow

switch; manual alarm.

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The preferred system is activation by zoned smoke

detection.

16.2 Ventilators operated only by a fusible link/thermal

device do not constitute a smoke extract "system".

16.3Power system controls and their connections should

maintain their integrity under design conditions in

a fire and should be designed to "fail" in the "on"

position.

16.4 Zone Control - The time taken for all ventilators

within a fire compartment to be fully operational

must not exceed 60 seconds from system

activation/smoke detection.

16.5 For natural ventilators used for life safety

purposes, in the event of power/system failure, the

equipment must failsafe in the "open" position.

17 MEZZANINE FLOORS

The effect of a mezzanine floor on smoke flow is not only

to induce more air entrainment but also to result in larger

quantities of cooler smoke. Therefore, there are additional

requirements when considering the smoke free clear layer to

ensure that the upper levels of the building remain free of

smoke for escaping people.

17.1 Clear Layer

The minimum clear layer, wherever possible, to the

underside of the smoke layer shall be.

3.0 metres above the floor level where the smoke is

contained to the floor or origin.

OR

3.0 metres above the uppermost occupied level of

mezzanine floor level where the smoke is allowed to

spill out from under the mezzanine floor:

1.0 Life safety, ie escape travel distances.

2.0 Smoke layer temperature, ie will "flashover"

occur.

3.0 Stock protection, ie maintaining a clear layer

above stored products.

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Smoke which has travelled laterally beneath a solid

mezzanine floor with entrain additional air as it

rotates around the balcony edge. Further entrainment

will occur as the smoky gases rise to the smoke

reservoir. The amount of entrainment is dependant upon

the width of the plume of smoky gases at the edge of

the mezzanine floor and the height of smoke must rise

from the mezzanine floor to the underside of the smoke

layer.

Thus, it is clear that the type of mezzanine floor may

affect the quantity and temperature of any smoke to be

extracted. For smoke control design purposes there.are

only two mezzanine types to be considered, Open

Mezzanine Floors and Solid Mezzanine Floors.

17.2 Permeable Mezzanine Floors

A mezzanine floor level within a single storey

industrial building is deemed to be a permeable

mezzanine floor if there is at least 25% free area of

the total floor plan area (not around the edge) evenly

distributed as openings over the whole floor area (see

Appendix 2 Reference 16). The calculation to determine

the free area should be the total floor plan area less

all obstructions to smoke flow through the mezzanine,

for example offices, storage areas, flooring material

etc.

If, by calculation, it can be proved that the

mezzanine floor has, and will continue to have, at

least 25% free area, then for smoke control purposes

it does not exist, since it has been proved that false

ceilings with this amount of free area do not

appreciably interfere with the flow of hot smoky

gases.

The design philosophy and methodology given in the

main body of this document shall apply, with the

proviso that the clear layer shall be, wherever

possible, at least 3.0 metres above the upper occupied

mezzanine floor level.

The smoke control designer shall ascertain whether the

25% criteria can be met initially, and advise his

client of the relevance and importance of the figure.

The smoke control system commissioning and maintenance

documents should also refer to the critical nature of

the 25% criteria, in an attempt to ensure that this

figure will not be reduced in the future.

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17.3 Solid (Non Permeable) Mezzanine Floors

Where mezzanine floors are solid or do not meet the

requirements of a permeable mezzanine floor, the

following design methods shall be applied.

There are two alternative design approaches which can

be considered for this type of mezzanine; containment

of the smoke to the floor of origin or to allow the

smoke to spill around the mezzanine floor edge and

rise to the roof smoke reservoir. The design

considerations for these alternative methods are

completely different and therefore these have been

shown separately.

17.3.1 Containment

This approach can be applied to the control of

smoke under solid mezzanine floors. Smoke from

a fire under the mezzanine is prevented from

spilling out of the area into the single

storey part of the building by means of smoke

curtains/screens, and is extracted from this

level.

In this instance, the recommendations

contained in the main body of this document

shall apply. However, due consideration shall

be given to both the smoke layer temperature,

(which may be high enough for flashover to

occur due to the limited height of rise from

the fire base to the underside of the smoke

layer), and the necessary depth of the smoke

curtains/screens required to prevent the

spillage of smoke from the area of containment

(which may, due to their depth, hamper

escape). Furthermore, the extract equipment

shall not exhaust at a rate likely to puncture

the smoke layer, as detailed within Sizing/

Siting of Equipment section of this document.

17.3.2 Smoke Flowing beyond a Mezzanine Floor Edge

As has been stated above, entrainment of air

into the smoke plume will occur as the smoke

spills about the edge of the mezzanine floor.

The amount of entrainment, and hence the mass

and temperature of the smoke to be extracted,

is dependant upon the following factors.

1 The height to the underside of the

mezzanine floor above the fire base.

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2 The depth of beam at the open edge of

mezzanine floor.

3 The width of the plume of hot smoky gases

at the edge of the mezzanine.

4 The height of rise of the smoke from the

underside of the mezzanine floor to the

bottom of the smoke layer.

5 The geometry of the rising plume of smoky

gases.

17.3.2.1 The Height to the Underside of the

Mezzanine Floor above the Fire Base

Consideration, must be given to the factors listed

within Section 7 of this document. It should be noted

however that since the smoke is not being contained

under the mezzanine but allowed to spill out of the

area, it is the determination of the flowing smoke

layer (its depth and its temperature) that are

critical. Relaxation of the minimum clear layer may

need to be sought in some circumstances.

The worst case of smoke generation must be

considered.

Research and evidence from real fires has shown the

largest quantity of smoke is produced when the

distance between the fire base and the underside of

the smoke layer is greatest. Thus, a fire should

always be considered as occurring on the lowest floor

level.

The amount of entrainment of air into the rising

plume of smoke beneath the mezzanine is dependant

upon its height of rise, ie from the fire base to the

underside of the flowing smoke Iayer.

The designer must state within the

calculations what criteria has been allowed.

17.3.2.2 The Depth of Beam at the Open Edge of

Mezzanine Floor

Research carried out, particularly in the areas of

smoke flowing under balconies in shopping centres and

atria buildings, has shown the importance of the

balcony or edge beam in the amount of entrainment

which occurs into the flowing smoke layer.

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It must be determined whether or not the edge beam is

"deep", relative to the flowing smoke layer (see

Appendix 2 References 2 and 16).

The designer must state within the

calculations what criteria has been allowed.

17.3.2.3 The Width of the Plume of Hot Smoky Gases

at the Edge of the Mezzanine

The amount of additional entrainment into the rising

plume of gases is related to the width of the plume of

smoke as it rotates about the mezzanine floor edge.

The use of void edge smoke curtains or screens to

limit this width is recommended in most instances.

The depth of these smoke curtains/screens should,

wherever practical, be 500mm below the depth of the

flowing smoke layer beneath the lowest transverse

obstruction to the smoke flow.

The designer must state within the

calculations what criteria has been allowed.

17.3.2.3 The Height of Rise of the Smoke from the

Underside of the Mezzanine Floor to the

Bottom of the Smoke Layer

Further entrainment into the smoky gases will occur

as the plume rises from the point at which it has

spilt out from under the mezzanine floor up to the

reservoir of smoke at roof level.

The amount of additional air which is drawn into the

rising plume is dependant upon its height of rise and

its geometric shape as detailed below.

Wherever possible the minimum height of rise of the

smoke plume shall be 3.0 metres above the uppermost

occupied level of mezzanine floor.

The designer must state within the calculations what

criteria has been allowed.

17.3.2.4 The Geometry of the Rising Plume of

Smoky Gases

Air can only be drawn into the rising plume of gases

on those faces of the gas stream which are in open

space. The smoke plumes are normally considered to

have four sides, a front, back and two ends.

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It will be noted therefore that there are a number of

configurations of smoke plumes to be considered, all

of which will introduce different quantities of air

into the rising smoky gases.

The designer must state within the calculations that

criteria has been allowed.

Single Sided Plume

This is rarely found since it can only entrain air

into one of its four sides, normally its front. For

this to occur, the plume must be as wide as the smoke

curtains/screens which limit its width (and be

prevented from increasing by the building structure),

and the rear of the plume must rise adjacent to the

face of the building structure.

Single Sided Plume with One End

This type of plume is also unusual, since the smoke

plume will rise with one end and either the front or

rear face adjacent to the building structure.

Single Sided Plume with Both Ends

This is one of the most common types of rising smoke

plumes from under mezzanine floors.

Smoke spilling out from under a mezzanine floor and

rising in free air except for the rear of the plum

which is adjacent to the structure of the building.

Two Sided Plume with Both Ends

The most common of smoke in this type of building,

and also the one which results in the largest mass of

coolest smoke to be extracted.

The stream of smoky gases from under the mezzanine

rises without restriction in free air.

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APPENDIX 1 - ASSOCIATED BRITISH STANDARDS

1 BS 4422. Part 5. 1988

ISO 8421 - S. 1988

Terms associated with fire, part 5, smoke control

2 BS 7346. Part 3. 1990

Components for smoke and heat control systems

Specification for smoke curtains

3 BS 7346. Part 1. 1990

Components for smoke and heat control systems

Specification for natural smoke and heat exhaust

ventilators

4 BS 7346. Part 2. 1990

Components for smoke and heat control systems

Specification for powered smoke and heat exhaust

ventilators

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APPENDIX 2 - REFERENCES

1 Theobald, C. Studies of Fires in Industrial Buildings

Part 1. The Growth and Development of Fire, Fire Prev

Sci. Technol, 17 (1977) pp 4-14.

2 Morgan, H P and Hansell, G O. Atrium buildings :

calculating smoke flows in atria for smoke control design.

Fire Safety Journal, 12 (1987) pp 9-35.

3 National Fire Protection Association. Smoke Management

in Malls, Atria and Large Areas. NFPA 92B. Quincy, M A.

NFPA (1991).

4 Thomas, P H et al. Investigations into the flow of hot

gases in roof venting. Fire Research Technical

Paper No. 7. HMSO, London (1963).

5 CEN Task Group Committee. Private Communications.

CEN/TC191/WG8/TG3, Design and Calculation Methods for

Smoke and Heat Exhaust Ventilation Systems, Brussels

(Dec 1993).

6 Thomas, P H et al. Design of roof venting for single

storey buildings. Fire Research Technical Paper No. 10,

HMSO, London (1964).

6 Hinkley, P L. The effect of vents on the opening of

The first sprinklers. Fire Safety Journal 11 (1986)

Pp 211-225.

8 Morgan, H P. A simplified approach to smoke venting

calculations. Building Research Establishment

information paper IP 19/85, BRE, Garston (1985).

9 Hinkley, P L et al. Experiments at the Multifunctioneel

Trainingcentrum, Ghent,0n the interaction between

sprinklers and smoke venting. Building Research

Establishment Report No. BR 224(1992), BRE,

Garston (1992).

10 Heselden, A J M. The interaction of sprinklers and roof

venting in industrial buildings the current knowledge.

Building Research Establishment.

11 Field, P. -How in-rack sprinkler protection was developed

for Donnington. Fire V79(973) (1986) pp 47-48.

12 Field, P. Effective sprinkler protection for high-racked

storage. Fire Surveyor 14(5) (1985) pp 9-25.

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13 Murrell, J V and Field, P. Sprinkler protection for post-

pallet storage in high racks. Fire Surveyor 19(1) (1990)

pp 16-20.

14 Murrell, J V and Field, P. Selection of sprinklers for

high-rack storage in warehouses. Building Research

Establishment Information Paper IP 5/88. Fire Research

Station, Borehamwood (1988).

15 Smoke Ventilation Association. SVA Guide to good practice

on application of smoke control equipment and systems.

Federation of Environmental Trade Associations,

Bourne End (1994).

16 Heselden, A J M. Efficient extraction of Smoke from a

thin layer under a ceiling. Fire Research Note No. 1001,

Fire Research Station, Borehamwood (1974).

17 Morgan, H P and Gardner, J P. Design principles for smoke

ventilation in enclosed shopping centres. Building

Research Establishment Report No. BR 186, BRE,

Garston (1990).

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APPENDIX 3

GROUP 1

CLASSIFICATION OF SPRINKLER CATEGORIES FOR INDUSTRIAL BUILDINGS

Breweries (excluding bottling sections) Restaurants and cafes

Power Stations

Butchers' slaughter houses

Creameries and wholesale dairies Abrasive wheel and power

manufacturers Cement works

Jewellery factories

GROUP 2

Bakeries and biscuit manufacturers

Chemical works with little fire hazard

(otherwise Group 3 or 4)

Motor car repair shops and large motor garages Motor vehicle

and accessories manufacturers Food - and preserved food

manufacturers

Machine factories including light metal manufacturers

GROUP 3

Cotton spinning mills

Bleacheries, dye-works

Brandy distilleries

Brush manufacturers

Printing offices

Tanneries,1eather good manufacturers

Cereal mills, grinding and peeling mills

Rubber and rubber articles manufacturers(excluding foam rubber)

Flax, jute, hemp mills

Aircraft manufacturers (excluding hangars)

Plastic and plastic products manufacturers (excluding foam)

Cardboard, paper and paper products manufacturers

Radio and television manufacturers (and appurtenances)

Sawing mills and wood using manufacturers

(including furniture factories)

Soap and wax products manufacturers

Textiles and carpets manufacturers

Sound, radio, film and television studios just as

Broadcasting rooms

Wool and worsted mills

Sugar works and refineries

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GROUP 4

Manufacturing and/or working up.

Celluloid

Paint, sealing wax, resin, turpentine, soot, tar Fire works,

lighting goods

Floor covering, linoleum etc

Aircraft hangars

Wood-wool Oil mills

Foam rubber, foam goods

GROUP 5

Warehouses with racking for combustible and non-combustible

materials in combustible packing. Not high bay warehouses or

palletised stock etc, as these are covered by other procedures.

SUB-DIVISION OF GROUP 5

GROUP 5/l

(Combustible and non-combustible materials in combustible

packing)

Electrical apparatus

Presswood boards

Glass and ceramic goods

Textiles

FoodMetal goods

Carpets

GROUP 5/2

Bottles with alcohol (packed in cardboard)

or alcohol in barrels

Pharmaceutical goods and cosmetics

Paper, cardboard

Roo£ing felt (tarred board) (stacked horizontally)

Veneering boards or timber

Furniture

Cork

Plastic products (excluding foams)

Varnish in tins (packed in cardboard)

Paper rolls (stored horizontally)

Floor covering

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GROUP 5/3

Roofing felt in rolls (stored vertically)

Rubber goods

Wood goods

Oil and wax paper

Cardboard and paper rolls (stored vertically)

Foams and plastics (packed and unpacked) and all

products packed in foam material

Cellulose

Wooden pallets, wooden battens and well aerated

stacks of wood

Celluloid

GROUP 5/4

Scraps of plastic or foam rubber, stored foam rolls and

latex foam rubber

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APPENDIX 4 - RATES OF HEAT RELEASE FOR VARIOUS FUELS

OF A KNOWN HEIGHT

TABLE A4.1 STORAGE RISKS

RHR (kW/m2)

Fuel

Stored Products Height

UK USA

(m)

Data Data

Wood crib 290 -

Wood crib 544 -

Wood crib 990 -

1582 -

Wood crib

- 1250

Wood pallets, stacked - 3500

Wood pallets, stacked - 6000

Wood pallets, stacked - 9000

Wood pallets, stacked 28

Crated furniture 82

Stacked sawn timber 134

160

Stacked chipboard

Cellulosics generally

- 350

Mail bags 524 -

Stacked cardboard 840 -

Cardboard reels 1030 -

Cardboard cartons - 1500

Cartons, compartmented, stacked 284 -

Cartons, electrical, goods 1130 -

Packaged goods - 870

Fibreglass components in cartons

PE fibreglass shower stalls in - 1250

cartons, stacked

Plastic bottles in cartons, - 4320

stacked

PVC bottles packed in cartons, - 3000

compartmented, stacked

PE bottles in cartons, - 5500

compartmented stacked 1750

PE bottles in cartons, stacked - 7500

PE letter trays, filled, stacked

PE trash barrels in cartons, - 1750

stacked - 4200

Plastic films in rolls - 5500

PP & PE films in rolls, stacked

PP tubs packed in cartons - 3900

compartmented, stacked

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APPENDIX 4 - RATES OF HEAT RELEASE FOR VARIOUS FUELS OF

A KNOWN HEIGHT

TABLE A4.1 Continued

RHR (kW/m2)

Stored Products Fuel

UK USA Height

Data Data (m)

PU Insulation packed, stacked - 1210 4.6

PU Insulation boards, rigit

foam in cartons, compartmented,

stacked - 1700 4.6

PS Insulation boar, rigid foam,

stacked - 2900 4.3

PS jars in cartons* - 12400 4.6

PS jars packed in cartons

compartmented, stacked* - 12500 4.6

PS tubs in cartons - 3450 4.3

PS tubs nested in cartons,

Stacked - 4750 4.3

PS toy parts in cartons - 1400 4.6

PS toy parts in cartons, stacked - 1800 4.6

Books, furniture 2160 - 3.0

 NB These figures appear to be anomalously high compared

With those following in the next four rows, which are

essentially the same product.

TABLE A4.2 SPECIFIC RISKS

RHR (kW/m2)

Fuel

Height

Stored Products

(m)

UK USA

Data Data

Furnished Offices 230 - -

Workshops for vehicles, petrol,

Paint 260 - -

Garages for trucks 1860

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TABLE A4.3 LIQUID FUEL RISKS

RHR (kW/m2)

Fuel

Height

Liquid Fuels

(m)

UK USA

Data Data

Industrial methylated spirit 740 650 -

Gasoline, petrol 1590 - -

Light fuel oil 1470 - -

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