A practical
guide to
Heating and
Ventilating
Contractors'
Association

Ductwork
Leakage
Testing

DW/143


DW/1 43 Ductwork Leakage Testing A practical guide

A practical guide to —

Ductwork
Leakage
Testing

Based on the requirements of

DW/144 specification for
sheet metal ductwork.
First published
Second edition (reprinted)
Third edition (reprinted)
Fourth edition (reprinted)
Fifth edition (revised)

1983
1986
1991

1994

2000

HEATING AND VENTILATING
CONTRACTORS' ASSOCIATION
Esca House, 34 Palace Court, London W2 4JG
Telephone: (020) 7313 4900 Fax: (020) 7727 9268
e-mail: web: www.hvca.org

DJ/ 1 43

COPYRIGHT © 2000
by the Heating and Ventilating Contractors Association All rights reserved

ISBN: 0-903783-30-4


DW/1 43 Ductwork Leakage Testing A practical guide

CONTENTS

Page
2
2

3

Acknowledgements
Cautions
Preface

PART ONE
Practical guide to leakage testing
Example of complete test sheet
Hints on leakage testing

4-6
7
8-9

PART TWO
Ductwork classification and air leakage
Appendix A: Air leakage from ductwork
Appendix B: Air leakage testing procedure

10
11-13
13-16

ACKNOWLEDGEMENTS
The HVCA records its appreciation and thanks to the persons and organisations who have freely

contributed to this work, and in particular to the members of the Drafting Panel.

Original DW/143 Drafting Panel 1983

J. H. G. Gardner (Chairman)
K. Angood
H. Brierley
H. Brocklehurst
P. Doyle
K. Waldron
K. Wheatley

Ductwork Group Technical Sub-Committee 2000
E. Poppleton (Chairman)
C. Collins
S. V. Howard
B. James
J. E. Murray
C. Robertson

G. P. Keller (Secretary, Ductwork Group)
J. M. Paynton (Former Secretary, Ductwork Group)
R. J. Miller (Former Secretary, Ductwork Group)
Front cover photograph by kind permission of Commtech Limited

FINANCIAL CAUTION
It is essential to realise that except where it is mandatory in Class C ductwork in DW/l44 this document
is not an endorsement of the routine testing of ducts but purely a guide to outline the procedures,
necessary for testing ducts for conformity with air leakage limits.
When proper methods of assembly and sealing of ducts are used a visual inspection will suffice for the
verification of a well engineered construction.

WHERE NOT MANDAT0R} DUCT LEAKAGE TESTING IS GENERALLY AN
UNJUSTIFIED SUBSTANTIAL EXPENSE.


2


DW/1 43 Ductwork Leakage Testing A practical guide

PREFACE

Edgar Poppleton Chairman, Technical Sub-Committee Ductwork Group, 2000

Specification DW/142, published by the HVCA in 1982, provided
for the first time in a long series of such publications for leakage limits over
the whole range of air pressures covered by the specification and (where
required) a test procedure to establish conformity.
Although leakage testing of high-pressure ductwork is still mandatory in DW/144
(as was the case in previous ductwork specifications issued by HVCA) the leakage
testing of ductwork designed to operate at low and medium pressures is required only
where so specified in individual job specifications.

Ductwork

With the retention of three pressure classifications in DW/144 it is hoped that

the designer, having control over performance standards, will find leakage
testing an unnecessary contract expense with regard to low and medium
pressure ductwork see note Financial Caution (page 2).
Ductwork contractors faced with a job calling for leakage testing should take this

requirement very seriously and satisfy themselves as the job progresses that the
required leakage rate or rates are within the limits set by the designer or the client.

The cost of making good an installation that has been found on completion to have
failed in this respect can be very expensive.

DW/144 specifies leakage limits for the ductwork alone, because the ductwork
contractor has no control over the leakage characteristics of the various components

which go to make up the whole of the air distribution system. Where a job
specification calls for a leakage limit for the whole system, it will be for the designer

or client to ensure that the leakage rates of the components are also within the
required limits.

Edgar Poppleton Chairman,
Technical Sub-Committee Ductwork Group, 2000


DW/1 43 Ductwork Leakage Testing A practical guide

Part One
A practical guide to
ductwork leakage
testing
I

tion is related to the highest test class of the
duct installation it is important that each duct
test zone should only be tested to a pressure
to cover the mean working pressure of that
particular section of ducting — see A.9(b).


2.4 Decide on the best way to isolate the
installation into test zones. When doing so,
the drawing office should bear in mind the
test pressures called for, the allowable air
losses, the work sequence on site and the
capacity of the test equipment.

General
With regard to air leakage, the responsibilities for ensuring the achievement of a satisfactory job is divided between the drawing
office, the factory and the ductwork installers

2.5 Arrange for the supply of suitable blanking
medium, e.g. heavy-duty polythene sheet.

on site. It is essential that there is full cooperation between them.

2.6 Make sure that all test points and blanking
devices can be reached with the minimum of

2 The drawing office

difficulty after the ductwork has been
installed.

2.1 Establish with the client or his representatives the class of ductwork called for in the
job specification, i.e.:
Class A: up to 500 Pa positive
Class B: up to 1000 Pa positive
Class C: up to 2000 Pa positive


2.2

Establish with the client or their represent-

ative that the required leakage rate or rates
are for the ductwork alone (eg excluding
dampers, fire dampers, air handling units,

2.7 Ensure that a reading can be obtained, by
planning test sections to have a permitted
leakage of approximately 25 per cent less
than the total volume generated by the test
rig at the pressure required for each section.

2.8 Provide the ductwork installers with details
of the test zones, duct operating pressures
and test pressures: and indicate the nature of

the blanking devices, gasket material and

fans, coils, attenuators, terminal boxes)
unless, by prior agreement, the casings
for any such items have been manufac-

2.9 Prepare test sheets giving the information

turedlsealed, by the supplier, to the required
standard of DW/l44.

called for on the sample test sheet shown on

page 7.

Additionally, establish the type of gasket

This information should indicate the test

material required in relation to the pressure
class/velocity of the system.

content, the surface area of the ductwork to
be tested, and the permitted leakage of each

Note:- Specific gasket material may be

section to be tested (this leakage is to be
expressed in litres per second per square

sealant to be used.

required in locations such as clean rooms,
hospitals etc.
If a leakage limit is laid down for the whole
system, it will be for the client or the designer to ensure that the leakage characteristics
of the components are acceptable.

2.3 Agree with the client or designer the test
pressure for each section of the installation.
(Note that whilst duct construction specifica-

metre of the ductwork surface area).


3

The factory

3.1

Take care to make components with a good
fit to minimise the use of sealant. A poor fit

cannot be remedied by the use of more
sealant — it will not work.


DW/1 43 Ductwork Leakage Testing A practical guide
3.2 Seal all longitudinal seams, laps. cross joints.
rivets and duct penetrations generally. in

4.5 Ensure the correct gasket material has

accordance with the requirements of

dance with the manufacturer's instructions.
Check with the drawings and specifications
where sealants are to be used on the cross
joints, and apply the sealants as necessary.
(Use only as much sealant as will do the job
— too much sealant is as bad as too little.)

been supplied and the application is in accor-


DW/l44.

3.3

Make sure that sealant is properly applied to

the ends of all lock forms and other types of

longitudinal seam, and to the corners and
junctions between those seams and the cross
joints.

3.4

4.6

Take special care to have as small a clearance

special attention to the sealing of joints
that will be difficult to reach after installation
of the ductwork.

as possible where there are penetrations of
the duct, as for example. damper spindles.

4.7 Fix the blanking plates or other types of temporary seal in the positions shown by the drawing office. (Ensure that the blanking material is
accessible for subsequent removal.)

3.5 Fit and seal branch connections carefully, as

required by DW/l44.

3.6

To be sure of minimum leakage. special care

4.8 At the earliest opportunity agree with the

must be taken in the fitting and sealing of

client or their representative on a progressive
testing programme.

access doors and panels etc.

3.7

To avoid the danger of breaking the seals, the

ductwork when ready to despatch to site
must be handled and loaded carefully.

4

Pay

Site work
For full details of procedure see Fig. I on Pages

8 and 9 and Appendix B Pages 14 and 15.


4.9

Before presentation to the client or their rep-

resentative. it is essential that a preliminary
test is carried out on each section of the work
at the earliest opportunity to ensure that the
ductwork has been correctly manufactured
and site sealant correctly applied.

4.10 If these preliminary tests show that the leakage is over the limit, then:

4.1

the proper use of the test rig.
It is expensive precision equipment. The
instructions must be read carefully and the

4.10.1 Look for any obvious places where

equipment handled in a responsible manner.

open access door or missing or

Understand

there may be leaks, for example, an

punctured


4.2

polythene

blanks.

Make sure that the right type of test rig is

Simple methods of locating any

available for the job. A rig suitable for highpressure leakage testing is seldom suitable or
economic for testing low- or medium- pressure ductwork, and vice versa.

leakage are:

a) by listening for them;
b) by feeling for them especially
with a wet hand;

c) by applying soapy water over

4.3

Note

that leakage testing is always done

under positive pressure even when the ductwork is to operate under negative pressure.


the seams or joints;

d) by (with the agreement of the
client) using a smoke pellet.

NOTE When smoke pellets are

4.4

Before installation, inspect all duct sections

to make sure that factory applied sealants
have not been damaged in transit. Make
good where any damage is noticed.

used, the smoke should he introduced downstream of the test rig
and not on its intake side.

5


DW/1 43 Ductwork Leakage Testing A practical guide
4.10.2 Reseal or correct where you have

found the leakage source(s).
Manufacturing

faults

be reported to the


should
factory

immediately.

4.10.3

Repeat

the test after allowing

enough time for the sealant to cure.

(Remember that sealants take
longer to cure in cold weather.
Read the sealant manufacturer's
instructions.)

4.1 1 When satisfied with the results of the
preliminary tests then:-

4.1 1.1 On successful completion of the
test, offer the section to the client or

their representative for formal
acceptance and signature on the test
sheet;

4.1 1.2 A permanent record of tests must

be retained.

4.12 As tests are satisfactorily completed, remove
all blanking-off devices.


DW/1 43 Ductwork Leakage Testing A practical guide

5 Example of a completed test sheet
Based on ductwork shown on pages 8 and 9
Test No

(;eneral

Name of job ..!'

2

Building Ref.
Part 1 — Physical details

a Section of ductwork to be tested
b

Drawing Number

c

Pressure Classification..'


RO.uI)ESiG.VERSi

d Test static pressure...?.cq
e Leakage factor
f

Surface area of duct under test

g Maximum permitted leakage..k
Part 2 — Test particulars

Q!19?
a Duct static pressure reading...
b Manufacturer and type of flow measuring device....
c Range of measurement of flow measuring device
d

Reading of flow measuring device

e

Interpreted air flow leakage rate...!'

f

Duration of test (normally 15 minutes)

Carried out S:naturej
by .?"'


Date of test

Printed

Name..Y'9(N

and Company

fROM RIG MANLF4cTURERS

DERIVED FROM CHART SLPPUED WITH RIG LSIVG

Witnessed by

di

SgnuIure)

Printed Name .4
and Company

Width and depth
or diameter

Periphery

Length

Area


millimetres

millimetres

metres

square metres

800x750

3100

17.55

54.40

600x650

2500

5.57

13.93

300x300

1200

1.20


1.44

-

305 dia.

958

7.04)

6.70

250 dia.

785

4.50

3.53

TOTAL

80.00


8

I

300 x


ru.

3050

TEST RIG
To be connectedand operatedin
accordanceWith the apparatus
instructions. In general, site on
firm level base and ensure gauges
are tc!ppedup with correct fluid
and zemed prior to commencing
test. Inclined manometerto read
leakage rate or pressure drop
which can be converted to leakage
rate by referenceto graph.

Tab car. notto ov.r pr..surls.
system undsrtest

WARNING

device.

Fit correct flow

SEQUENCE OF TEST
1. Ptepare test sheet
2. Connect and adjusttest rig to correct pressure.
3. Read off leakage rate.

4. Reseal ifnecessary(allow time to cure).
5. Mintthn test for 15 mins.
6. Switch off and allow to
7. Reapply test pressure and check reading.
8. Record details on test sheet and obtain signature.

dfrectlytothe
ductwork uider test.

should be couuected

of duct pressure
the tube fre. the

luordertoavold

600 x 650

Takespecialcare
with inaccessible
joints

Hints on Ductwork Leakage Testing

Testing A practical guide

FLEX
Keep length to a minimum
and make sure that both
end connectionsare correctly

sealed and that the flexible
duct itselfhas no leaks.

Fig.

DW/1 43 Ductwork Leakage

to read pleasure
m test

Vermaixjsneter

test

700

800 x 750

Blank at convenient
Placeweli access
for ease of removal

800 x

-

A practical guide

D1W No. 20433/12


HOW TO FIND LEAKS
—
I.I..eok
perlicularlyatblanks,accesaopeninp
and difficukjoints.
2. Listen
Withtestngnmningleaks
shonidbeaudible.
— running yourhand (particularlyifwet)
3. Feel
over joints can help to locate leakL
4. Soap and Water — paint overjoints and look kr bubbles.
5. Smoke Pellet — placed inkIn ductwork (obtainpermission kr use)

er. Rneinherto
blaM inum
and

Blank offall open

Ductwork Leakage Testing

The dimensions on this ductwork are used in an example on page 7

DW/1 43


Page blank
in original



DW/1 43 Ductwork Leakage Testing A practicalguide

Part Two

6.4 Air leakage testing
Air leakage testing of low and medium pres-

sure ductwork is not mandatory under the

6 This section, apart from Appendix 'B', is

specification DW/l44.
Air leakage testing of high pressure ductwork
is mandatory under the specification DW/l44
and for details of testing procedure refer to
Part 1 of this guide.

extracted from DW/144 — Specification for
Sheet Metal Ductwork, and for ease of reference the numbering as in DW/144 has been
retained. The leakage limits for EUROVENT
classifications A, B and C, as set out in their
document 2/2 (Air Leakage in Ductwork) have
been adopted for the low pressure, medium
pressure and high pressure Class C classifications.

Ductwork classification and
air leakage
6.1 Classification and air leakage limits
Ductwork classification and air leakage

limits are set out in Table I.

6.2 Compatibility with CEN
The leakage factors used in Table 1 for
Classes A, B and C are the same as those for
the classes similarly designated in the CEN
Document Pr EN 12237/Pr EN 1507.

6.3 Leakage at various pressures; and other
relationships

Applying the limits specified in Table I,
Appendix A (Table 17) sets out the permitted
leakage at each of a series of pressures up to

a maximum for each class. Included in that
appendix is a graphical presentation of the
pressure/leakage relationship (see fig 178).
Appendix A, also gives details of the basis
for the leakage limits specified in
Table 1.

Table 1 Ductwork Classification and Air Leakage Limits
Static pressure limit

Ductpressureclass
1

Low-pressure — Class A


Medium-pressure — Class B
I High-pressure — Class C

Positive

Negative

velocity

Air leakage limits
litres per second per square
metre of duct surface area

5

2

3

Pa

Pa
500

rn/s
10

0.027 x p01

750

750

20

0.009 x p°'65

-40

0.003 x p°-65

500
1000

2000

Where p is the differential, pressure in pascals.

10

Maximum air'


DW/1 43 Ductwork Leakage Testing A practical guide

APPENDIX A
Air leakage from
ductwork

—750 Pascals.


Class C
High pressure ducts suitable for a maximum
positive operating pressure of 2000 Pascals
and a maximum negative pressure of —750
Pascals.

A.1 Introduction

A.3 Leakage from ductwork
Leakage from ducted air distribution systems

is an important consideration in the design
and operation of ventilation and air conditioning systems. A ductwork system that has
limited air leakage, within defined limits, will

ensure that the design characteristics of the
system can be maintained. It will also ensure
that energy and operational costs are maintained at optimum levels.
Ductwork constructed and installed in accordance with DW/144 should minimise a level
of air leakage that is appropriate to the oper-

Leakage from sheet metal air ducts occurs at

the seams and joints and is therefore proportional to the total surface area of the ductwork
in the system. The level of leakage is similarly related to the air pressure in the duct system and whilst there is no precise formula for
calculating the level of air loss it is generally
accepted that leakage will increase in proportion to pressure to the power of 0.65.

The effect of air leakage from high pressure/velocity ductwork is critical in terms of


ating static air pressure in the system.

system performance. energy consumption

However, it is recognised that the environment in which systems are installed is not
always conducive to achieving a predictable

and the risk of high frequency noise associated with leakage.
These problems are less critical with medium

level of quality in terms of system air leakage

pressure/velocity systems. but should be

and it is therefore accepted that designers

considered.

may sometimes require the systems to be tested in part or in total. It should be recognised
that the testing of duct systems adds a significant cost to the installation and incurs some
extra time within the programme (See 4.1 and
6.4 of DW/144 re mandatory testing).

Low pressure/velocity ducts present the
lowest risk in terms of the effect of leakage on
the effective operation of the system.

A.4 System leakage loss
As there is no direct relationship between the


A.2 Duct pressure
Ductwork constructed to DW/144 will be
manufactured to a structural standard that is
compatible with the system operating pressure.
There are three classes of duct construction to
correspond with the three pressure classifications:

Class A

Low pressure ducts suitable for a maximum
positive operating pressure of 500 Pascals
and a maximum negative pressure of —500
Pascals.
Class B

Medium pressure ducts suitable for a maxi-

mum positive operating pressure of 1000
Pascals and a maximum negative pressure of

volume of air conveyed and the surface area
of the ductwork system required to match the
building configuration it is difficult to express
air leakage as a percentage of total air volume.
Similarly, the operating pressure will vary
throughout the system and as leakage is related to pressure the calculations are complex.
However, it is generally accepted that in typical good quality systems the leakage from
each class of duct under operating conditions
will be in the region of:
6%

Class A low pressure

Class B medium pressure 3%
2%
Class C high pressure


DW/1 43 Ductwork Leakage Testing A practicalguide

A.5 Specifying air leakage testing
both the cost and programme

In the case where a random test is selected for
medium pressure ducts the following clause is
suggested for inclusion by the designer.

implications associated with testing ducts for
leakage, the designer may, for example indi-

mum of 10% of the duct system to be tested for

Respecting

The designer shall select at random a inaxi-

cate that a particular system is tested as

air leakage. The duct shall be tested at the

follows:

a) High pressure ducts — all tested.

pressure recommended in Table 17 of DW/144

b) Medium pressure ducts —

10%

for the classification for the section of the
of the

ductwork shall be selected at random and
tested.
c) Low pressure — untested.

Table 17 Air leakage rates
Maximum leakage of ductork
Static

Low-pressure
Class A

pressure

Medium-pressure
Class B

High-pressure
Class C


differential

ductwork that is to be tested.
The tests shall be carried out as the t'ork proceeds and prior to the application of thermal
insulation.

In the event of test failure of the randomly
selected section, the designer shall have the
right to select two further sections at random
for testing. Where successive failures are
identified there shall be a right to require the
contractor to apply remedial attention to the
complete ductwork system.

Lit:es per second per square metre of su:ce area

Pa

100

0.54

0.18

200

0.84

0.28


300

1.10

0.37

400

1.32

0.44

500

1.53

0.51

There may be situations on a project where

0.58

0.19

700

0.64

0.21


800

0.69

0.23

900

0.75

0.25

1000

0.80

-

0.27

1100

0.29

1200

0.30

1300


0.32

1400

0.33

1500

0.35

1600

0.36

1700

0.38

1800

0.39

1900

0.40

2000

0.42


Note: Recommended 'mean' test pressures are highlighted in
bold type with the actual selection being left to the test

12

evidence of the calculations used to arrive at
the allowable loss for the section to be tested
and the client, or his agent, shall witness and
sign the results of the test.

A.6 Special cases

600

operator.

The contractor shall provide documented

circumstances dictate that special consideration be given to containing air losses, e.g. a
long run of ductwork may incur a disproportionate level of air loss.
In cases such as this example the designer can
specify an improved standard of airtightness,
i.e. 80% of allowable loss for Class 'B' ducts.
The designer should not specify a Class 'C'
test at Class 'C' pressure for a Class 'B' duct.

A.7 Suggested range of testing
cautionary note on page 2 of this guide)
100% test
• High pressure ducts

• Medium pressure ducts
see A5
• Low pressure ducts
Untested
Untested
• Exposed extract systems
• Ceiling void extract
Untested
systems
• Secondary ducts from
VAV or fan coil units
Untested
• Flexible ducts
Untested
(see


—

• Final connections and
branches to grilles and
diffusers

DW/1 43 Ductwork Leakage Testing A practical guide

Appendix

B

Untested


A.8 Testing of plant items

Air leakage testing
Procedure

Items of inline plant (eg. Figs. 168 to 175) will

not normally be included in the air leakage
test. The ductwork contractor may include
such items in the test if the equipment has a
certificate of conformity for the pressure class

and air leakage classification for the system
under test.

A.9 Designer's calculations

B.1 General
Section 6 (page 10) of this specification deals

with the performance requirements of ductwork in respect of air leakage, and Table 17
(Appendix A) tabulates the limits of leakage

applicable to each class of ductwork.
Appendix B is solely concerned with recommendations for the testing procedure.

The designer can calculate with reasonable

accuracy the predicted total loss from a system by:

a) Calculating the operating pressure in
each section of the system.

b) Calculating the surface area of the

B.2 Extent of ductwork to be
tested
B.2.1 The procedure set out in this section

ductwork in each corresponding pressure
section.

is limited to the ductwork and those
items of in-line plant equipment that
are manufacturedlsealed to the crite-

c) Calculating the allowable loss at the

ria set out in Table 1 (also see

operating pressure for each section of the
system (see Table 17 for allowable leakage figures).

A.1O Variable

pressures in systems

Designers can achieve significant cost savings

by matching operating pressures throughout

the system to constructional standards and
appropriate air leakage testing. e.g. the practice of specifying construction standards for
whole duct systems based on fan discharge
pressures may incur unnecessary costs on a
project.

For example, some large systems could well
be classified for leakage limits as follows:
Plant room risers
Class C
Main floor distribution
Class B
Low pressure outlets
Class A

Appendix A.8).

B.2.2 The extent of the ductwork to be
tested and the method of selection
(where not included in the job specification) should be determined in
collaboration between the designer
and the ductwork contractor with
consideration having been given to
the recommendations outlined in
Appendix A.

B.2.3 Fit blanking devices in accordance
with the drawing office guidance
notes (Part I, Section 2). To enable a
blank to be cut out after the testing is


completed, access may be required
adjacent to each blank.

B.2.4 Alternatively,

rigid removable

blanking plates can be used,
although this involves remaking
joints.

13


DW/1 43 Ductwork Leakage Testing A practical guide
Fig. 178 Permitted leakage at various pressures

Leakage in litres per second per square metre duct surface area

**
*
*

*-t
—

'I

*


*
*-t
*
*

Cl


DW/1 43 Ductwork Leakage Testing A practical guide

B.3 Testing to be completed
before insulation, etc.

B.6 Test pressures and leakage
rates

shall be satisfactorily completed
before insulation or enclosure of the ductwork and before terminal units (if any) are

The maximum permissible leakage rates for

fitted.

various classes of ductwork are set out in

Testing

the full range of pressures are given in Table
17. The recommended test pressures for the


Table 2, and unless otherwise specified, the
choice of test pressure shall be at the discretion of the test operator.

B.4 Re-testing procedure where
necessary
B.4.1 The air leakage rate for any section

B.7 Test rig

shall not be in excess of the permitted rate for that section. If a first test

B.7.1 The accuracy of the test rig shall be

produces leakage in excess of the
permitted maximum, the section

within:
± 10 per cent of the indicated flow

shall be resealed and retested until a
leakage not greater than the permit-

rate, or 0.4 litres per second.
whichever is the greater and
± 5 per cent at the indicated static
pressure in the duct under test.

ted maximum for that section is
achieved.


B.4.2 If at the time of witnessing the test it

B.7.2

The test rig shall be inspected by

the user before use on site, and

is apparent that excessive additional
sealing of seams or joints has been

shall have a calibration certificate,
chart or graph dated not earlier than
one year before the test for which it
is used.

done in order to meet the required
leakage level, the section of ductwork under test shall not be counted

as part of the tested ductwork,
B.7.3

except where the whole of the ductwork is required to be tested.

A schematic arrangement of an air
leakage test is given in Fig. 2.

B.8 Procedure


B.5 Minimum area to be tested
The section of ductwork to be tested shall

B.8.1 The section of ductwork to be test-

have an area large enough to enable the test
rig to register a measurable leakage.

ed for air leakage shall be sealed.

Main ducts should be provided

Table 2 Recommended maximum test pressures (with leakage rates)
Maximum leakage of ductwork

--

Static
pressure
differential

Low-pressure
Class A

Medium-pressure
Class B

High-pressure

I


2

3

4

Pa
200
400
800
1200
1500

Class C

Litres per secnd per square metre 'of surface area
0.84
1.32
0.44
0.69
0.30
0.35

-


DW/1 43 Ductwork Leakage Testing A practical guide

with flanged joints to enable


B.9.1 Complete Part 1 of the Test Sheet.

blanking plates to be fitted, while

B.9.2

small open ends may be sealed with
polythene or inflatable bags, which
should be left in position until final
connections are made.

Connect test rig to section of duct-

work to be tested.

B.9.3 Adjust test rig until the static pressure differential is obtained.

B.8.2

On

low-pressure systems, final

B.9.4

grille spigots made as a second fix

within the permitted rate. (No addition shall be made to the permissible
leakage rate for access doors, access

panels or dampers where these are
included in the ductwork.)

operation shall be excluded from the
test. The joint shall, where practica-

ble, be checked by external visual
examination.

B.8.3 Sufficient time shall be allowed
between installation and leakage

B.9.5 Maintain the test for fifteen minutes
and check that the leakage rate has
not increased.

testing for sealants to cure.

B.8.4

B.8.5

Special

Check that the measured leakage is

care must be exercised in

making all joints which fall outside
the scope of the testing procedure.

i.e., joints between tested sections
of ductwork and between ductwork
and items of in-line equipment not
included in the test.

B.9.6

Due notice of tests shall be given, so

B.9.7

Reduce

pressure in section to zero

by switching off the fan; then imme-

diately re-apply test pressure to
establish that the air leakage rate is
not greater than the previous reading.
Record details on Part 2 of the Test

Sheet and complete, including witnessing.

that arrangements for witnessing the
tests can be made.

B.9 Testing sequence

B.1O


Air leakage test sheet

A example of a suitable Test Sheet is give
on page 7.

The recommended sequence of testing is as
follows.

Fig. 2 Schematic arrangement of an air leakage test
Blanking
plate

Flow measunng device
(may be located on
the suction side of
the fan(

Duct under test

fan

Duct test
pressure gauge

Inclined gauge

16

Bleed valve (not necessary

if variable speed
fan used(


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