ISO 21927-2:2006

INTERNATIONAL ISO
STANDARD 21927-2
First edition
2006-11-15
Smoke and heat control systems —
Part 2:
Specification for natural smoke and heat
exhaust ventilators
Systèmes de contrôle de fumée et de chaleur —
Partie 2: Spécifications pour les dispositifs d'évacuation naturelle des
fumées et de la chaleur
Reference number
©
ISO 2006
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©  ISO 2006
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Published in Switzerland
ii © ISO 2006 – All rights reserved

Contents Page
Foreword. iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 1
4 Symbols . 4
5 Design requirements . 5
5.1 Initiation device. 5
5.2 Opening mechanism. 6
5.3 Opening of the ventilator . 6
5.4 Size of the geometric area . 6
5.5 Inputs and outputs (connections). 7
6 General testing procedures . 7
7 Aerodynamic free area of the ventilator. 7
8 Performance requirements and classification. 7
8.1 Reliability . 7
8.2 Opening under load. 8
8.3 Low ambient temperature . 9
8.4 Wind load. 10
8.5 Resistance to heat . 10
9 Evaluation of conformity. 11
9.1 General. 11
9.2 Type testing. 11
9.3 Factory production control (FPC) . 11
10 Marking . 11
11 Installation and maintenance information.12
11.1 Installation information . 12
11.2 Maintenance information . 12
Annex A (normative) General testing procedures . 13
Annex B (normative) Determination of the aerodynamic free area. 14
Annex C (normative) Test method for reliability. 28
Annex D (normative) Test method for opening under load . 29
Annex E (normative) Test method for low ambient temperature . 30
Annex F (normative) Test methods for wind load . 32
Annex G (normative) Test method for heat exposure . 33
Annex H (normative) Direct field of application for SHEVs . 36
Bibliography . 40

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 21927-2 was prepared by Technical Committee ISO/TC 21, Equipment for fire protection and fire fighting,
Subcommittee SC 11, Smoke and heat control systems and components.
ISO 21927 consists of the following parts, under the general title Smoke and heat control systems:
⎯ Part 1: Specification for smoke barriers
⎯ Part 2: Specification for natural smoke and heat exhaust ventilators
⎯ Part 3: Specification for powered smoke and heat exhaust ventilators
iv © ISO 2006 – All rights reserved

Introduction
In a fire situation, smoke- and heat-exhaust ventilation systems create and maintain a smoke-free layer above
the floor by removing smoke. They also serve simultaneously to exhaust hot gases released by a fire in the
developing stages. The use of such systems to create smoke-free areas beneath a buoyant layer has become
widespread. Their value in assisting in the evacuation of people from buildings and other construction works,
reducing fire damage and financial loss by preventing smoke damage, facilitating access for fire-fighting by
improving visibility, reducing roof temperatures and retarding the lateral spread of fire is firmly established. For
these benefits to be obtained, it is essential that smoke- and heat-exhaust ventilators operate fully and reliably
whenever called upon to do so during their installed life. A smoke- and heat-exhaust ventilation system
(referred to in this part of ISO 21927 as a SHEVS) is a system of safety equipment intended to perform a
positive role in a fire emergency.
INTERNATIONAL STANDARD ISO 21927-2:2006(E)

Smoke and heat control systems —
Part 2:
Specification for natural smoke and heat exhaust ventilators
1 Scope
This part of ISO 21927 specifies requirements and gives test methods for natural smoke- and heat-exhaust
ventilators that are intended to be installed in a roof and/or wall as a component of a natural smoke- and heat-
exhaust system.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 6182-1, Fire protection — Automatic sprinkler systems — Part 1: Requirements and test methods for
sprinklers
ISO 7240-7, Fire detection and alarm systems — Part 7: Point-type smoke detectors using scattered light,
transmitted light or ionization
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 13943 and the following apply.
3.1
aerodynamic free area
product of the geometric area multiplied by the coefficient of discharge
3.2
ambient
properties of the surroundings
3.3
automatic activation
initiation of operation without direct human intervention
3.4
aspect ratio
ratio of length to width
3.5
automatic natural smoke- and heat-exhaust ventilator
smoke- and heat-exhaust ventilator that is designed to open automatically after the outbreak of fire if called
upon to do so
NOTE Automatic natural smoke- and heat-exhaust ventilators can also be fitted with a manual control or release
device.
3.6
coefficient of discharge
C
v
ratio of actual flow rate, measured under specified conditions, to the theoretical flow rate, through the
ventilator, as defined in Annex B
NOTE 1 The coefficient takes into account any obstructions in the ventilator, such as controls, louvers and vanes, and
the effect of external side winds.
NOTE 2 Also called aerodynamic efficiency.
3.7
dual-purpose ventilator
smoke- and heat-exhaust ventilator that has provision to allow its use for comfort (i.e. day-to-day) ventilation
3.8
exhaust ventilator
device for the movement of gases out of the construction works
3.9
fire-open position
configuration of the ventilator specified by its designer to be achieved and sustained while venting smoke and
heat
3.10
gas container
vessel containing gas in a compressed form, the energy of which, when released, opens the ventilator
3.11
geometric area
A
v
area of the opening through a ventilator, measured in the plane defined by the surface of the construction
works, where it contacts the structure of the ventilator
NOTE No reduction is made for controls, louvers or other obstructions.
3.12
initiation device
device that activates the operating mechanism of the component (e.g. of a damper or a ventilator) on receipt
of information from a fire detection system or thermal device
3.13
manual operation
initiation of the operation of a smoke- and heat-exhaust ventilator by a human action (e.g. pressing a button,
or pulling a handle)
NOTE A sequence of automatic actions in the operation of a smoke- and heat-exhaust ventilator started by the initial
human action is regarded as manual operation for the purposes of this part of ISO 21927.
3.14
manually opened natural smoke- and heat-exhaust ventilator
natural smoke- and heat-exhaust ventilator that can be opened only by a manual control or release device
3.15
mass flux
total mass of gases crossing a specified boundary per unit time
2 © ISO 2006 – All rights reserved

3.16
natural ventilation
ventilation caused by buoyancy forces due to differences in density of the gases because of temperature
differences
3.17
opening mechanism
mechanical device that operates the ventilator to the fire-open position
3.18
opening time
period between the information to open being received by the ventilators and achieving the fire-open position
of the ventilator
3.19
projection area
cross-sectional area of the natural smoke- and heat-exhaust ventilator in its fire-open position above the plane
of the roof, at a right angle to the side-wind flow
3.20
range of natural smoke- and heat-exhaust ventilators
ventilators of various sizes having the same method of construction and the identical number and type of
opening devices
3.21
smoke- and heat-control system
arrangement of components installed in a construction works to limit the effects of smoke and heat from a fire
3.22
smoke- and heat-exhaust system
smoke and heat control system that exhausts smoke and heat from a fire in a construction works or part of a
construction works
3.23
smoke- and heat-exhaust ventilation system
SHEVS
components jointly selected to exhaust smoke and heat in order to establish a buoyant layer of warm gases
above cooler and cleaner air
3.24
smoke- and heat-exhaust ventilator
SHEV
device specially designed to move smoke and hot gases out of a construction works under conditions of fire
3.25
thermal device
temperature-sensitive device that responds to initiate a subsequent action
3.26
throat area
smallest cross-sectional area of the flow path through the ventilator
3.27
ventilator
device for enabling the movement of gases into or out of the construction works
3.28
wind-sensitive control system
control system designed to control two or more banks of ventilators on separate elevations so that only the
ventilators not subject to positive wind pressures open in case of fire
3.29
wall
external building surface with an inclination of more than 60° relative to the horizontal
3.30
roof
external building surface with inclination of 60° or less relative to the horizontal
NOTE Shed roofs, independent of inclination angle, are considered to be part of roofs.
4 Symbols
Symbol Definition Unit
A any number used in the classifications
A aerodynamic free area, expressed in square meters (m )
a
A nozzle exit area (for open jet facilities), expressed in square meters (m )
n
A projection area of the ventilator for the side-wind flow, expressed in square meters (m )
pr
A horizontal cross-section area of the settling chamber, expressed in square meters (m )
sc
A geometric area of the ventilator, expressed in square meters (m )
v
B width of the open hole of the settling chamber, expressed in meters (m)
B width of nozzle exit area in open jet facilities, expressed in meters (m)
n
B maximum width of the ventilator in the fire-open position, expressed in meters above (m)
v
the upper surface of the settling chamber
C coefficient of discharge, dimensionless _
v
C coefficient of discharge without side-wind influence, dimensionless _
v0
C coefficient of discharge with side-wind influence, dimensionless _
vw
H height of nozzle exit area in open jet facilities, expressed in meters (m)
n
H maximum height of the ventilator in the fire-open position above the upper surface of (m)
v
the settling chamber, expressed in meters
L length of the open hole of the settling chamber, expressed in meters (m)

m mass flow rate entering the settling chamber, expressed in kilograms per second (kg/s)
ing
p ambient pressure, expressed in pascals (Pa)
amb
p wind-stagnation pressure, expressed in pascals (Pa)
d
p internal static pressure, expressed in pascals (Pa)
int
p internal static pressure without side wind, expressed in pascals (Pa)
int, v0
p internal static pressure with side wind, expressed in pascals (Pa)
int, vw
4 © ISO 2006 – All rights reserved

T temperature, expressed in degrees Celsius (°C)
∆T temperature difference, expressed in Kelvin (K)
V side-wind velocity, expressed in meters per second (m/s)
∞
V mean velocity of the settling chamber, expressed in meters per second (m/s)
m, sc
V mean nozzle velocity, expressed in meters per second (m/s)
n
V local velocities in plane above settling chamber, see Figure B.6, expressed in (m/s)
sc
meters per second
W snow load, expressed in pascals (Pa)
s
W wind load, expressed in pascals (Pa)
w
W design wind load, expressed in pascals (Pa)
wd
α opening angle of the ventilator, expressed in degrees °
β angle of attack, expressed in degrees °
β incidence angle at which the smallest value of C obtained with side wind occurs, °
crit vw
expressed in degrees
θ angle of installation of ventilators on a roof, expressed in degrees °
∆p pressure difference, expressed in pascals (Pa)
∆p reference-pressure difference between the static pressure in the settling chamber (Pa)
v0
and the ambient pressure without side wind, expressed in pascals
∆p reference-pressure difference between the static pressure in the settling chamber (Pa)
vw
and the ambient pressure with side wind, expressed in pascals
∆p pressure difference between the static pressure in the settling chamber and the (Pa)
int
ambient pressure, expressed in pascals
ρ density of air, expressed in kilograms per cubic meter (kg/m )
air
5 Design requirements
5.1 Initiation device
5.1.1 General
To ensure that the natural smoke and heat ventilator opens in the event of a fire, it shall be fitted with an
automatic initiation device.
Each ventilator shall be fitted with one or more of the following automatic initiation devices:
a) thermal initiation device;
b) initiation device activated by an electrical signal from a remote source, e.g. a smoke and heat detector
system, the interruption of electrical supply or a manually actuated “fire override” switch;
c) pneumatic initiation device, e.g. a pneumatic signal or a loss of compressed air;
d) initiation device able to respond to other types of release signal.
The response behaviour of thermal automatic initiation devices shall comply with the requirements of
ISO 6182-1. Smoke detectors shall comply with the requirements of ISO 7240-7. In addition, a manually
operated initiation device may be fitted.
A pneumatic non-fail-safe SHEV, which does not open automatically on loss of power, shall have at least a
thermal device and one power source that is mounted directly in the SHEV, unless the required control panel
monitors the lines to the SHEV and indicates a failure.
In some specific design cases where it is suitable that the ventilator shall be only manually initiated, the
ventilator may be installed without an automatic initiation device.
5.1.2 Thermal initiation device
Any thermal initiation or release device shall be within the ventilator and shall be exposed to the hot gas
entering the closed ventilator.
There are two exceptions to this requirement, where an automatic thermal initiation or release device shall not
be fitted to the ventilator:
a) if the ventilators are installed as wall-mounted ventilators;
NOTE Adverse wind conditions can cause a ventilator, which has been opened by the automatic initiation
device, to let in air and not remove heat and smoke.
b) in specific design cases where it is suitable that the ventilators are only manually initiated.
5.2 Opening mechanism
5.2.1 General
The ventilator shall be provided with an opening mechanism with energy within the ventilator, e.g. gas
containers, spring systems, electrical power supply and/or with an external energy source. For the external
links, the manufacturer shall specify the operating requirements for the initiation device and the opening
mechanism, e.g. voltage, energy.
5.2.2 Integral gas containers
Any gas container forming an integral part of the ventilator shall be equipped with a pressure-release device to
prevent an explosion if the container overheats.
5.3 Opening of the ventilator
For on-site testing purposes, there are two types of ventilators:
a) type A, which are able to be opened into their fire-open position;
b) type B, which are able to be opened into their fire-open position and closed remotely.
5.4 Size of the geometric area
The size and form of the geometric area shall be such that it complies with the limitation set by the test
apparatus available for the heat exposure test.
6 © ISO 2006 – All rights reserved

The side length shall not exceed 2,5 m and the aspect ratio of the geometric area shall not exceed 5:1 when
using the simple assessment procedure to determine the aerodynamic free area; see Clause B.1.
NOTE As of the publication date of this part of ISO 21927, maximum dimensions of the test apparatus for the heat
exposure test are in the range of 3 m.
For ventilators larger than the largest ventilator tested in accordance with Annex G, an assessment of the heat
exposure effect shall be made by the testing station to ensure that the performance is not negatively affected.
5.5 Inputs and outputs (connections)
The SHEV shall be equipped with inputs and/or output that allow its connection with the control panel and
power supplies.
6 General testing procedures
For type approval testing, tests shall be carried out in the sequence specified in Clause A.1.
For each test, a test report shall be prepared in accordance with Clause A.2.
Some of the tests mentioned may be omitted when type testing a new product belonging to a product range
that has been tested if only detail changes have been made.
The use of additional functions to smoke ventilation (e.g. daily ventilation) and/or add-ons to the SHEVs are
permitted if they do not negatively alter the performance of the SHEV.
7 Aerodynamic free area of the ventilator
The aerodynamic free area of the ventilator shall be determined in accordance with Annex B.
For roof-mounted ventilators, the aerodynamic free area is written A .
a Roof
For wall-mounted ventilators, the aerodynamic free area is written A .
a Wall
8 Performance requirements and classification
8.1 Reliability
8.1.1 Reliability classification
The ventilator shall be classified as one of the following:
a) Re A;
b) Re 50;
c) Re 1 000.
The designation A, 50 and 1 000 represents the number of openings into the fire-open position and closing
under no applied load in accordance with Annex C.
8.1.2 Reliability performance
The ventilator shall open, reach its fire-open position not more than 60 s after actuation without damage and
remain in position without an external energy supply (until reset).
8.1.3 Dual purpose ventilator
If the ventilator is a dual purpose ventilator, it shall open to its normal comfort position when tested under no
load 10 000 times in accordance with Annex C prior to testing the same ventilator under 8.1.1 and 8.1.2.
8.2 Opening under load
8.2.1 Loads
8.2.1.1 Snow-load classification
The ventilator shall be classified as one of the following:
a) SL 0;
b) SL 125;
c) SL 250;
d) SL 500;
e) SL 1 000;
f) SL A.
The designations 0, 125, 250, 500, 1 000 and “A” represent the test snow load, expressed in pascals, applied
when the ventilator is tested in accordance with Annex D.
NOTE A ventilator classified SL 0 can be installed in accordance with the manufacturer’s instructions with a minimum
angle of installation > 45° from the horizontal (combining roof pitch and vent pitch (see Figure 1), except where the snow is
prevented from slipping from the ventilator, e.g. by wind deflectors.
Except for SL 0 for ventilators fitted with deflectors, the snow-load classification should not be less than
SL = 2 000 d, where d is the depth of snow, expressed in metres, that can be contained within the confines of
the deflectors.
8.2.1.2 Load due to side-wind simulation
To simulate the side-wind influence, the ventilator shall be subjected to the most unfavourable wind direction
to a side wind of 10 m/s velocity when tested in accordance with Annex D.
This test does not apply for wall-mounted SHEVs.
8.2.2 Performance under load
The ventilator shall open, reach its fire-open position not more than 60 s after actuation and remain in position
without an external energy supply (until reset), when tested under the snow load appropriate to its
classification and under the specified side wind in accordance with Annex D.
For ventilators fitted with wind deflectors, the deflectors shall be at least 80 mm from the nearest part of the
ventilator and they shall not be fitted in such a way to encourage snow or ice to collect to the detriment of the
operation of the ventilator.
8 © ISO 2006 – All rights reserved

It is recommended that louver-type ventilators be classified not less than SL 500 when used in sub-zero
conditions.
This test does not apply for wall-mounted SHEVs.

Key
1 ventilator
2 roof
Figure 1 — Combined roof pitch and vent pitch angle > 45° from the horizontal
8.3 Low ambient temperature
8.3.1 Classification
The ventilator shall be classified as one of the following:
a) T(− 25);
b) T(− 15);
c) T(− 05);
d) T(00);
e) T A.
The designations 25, 15, 05 and “A” represent the number of °C below zero at which the ventilator is tested in
accordance with Annex E. T(00) ventilators are regarded as suitable only for use in construction works where
the temperature is above 0 °C.
8.3.2 Performance at low temperature
When tested in accordance with Annex E, the opening mechanism of a classified ventilator, except those
classified as T(00) (see 8.3.1), shall operate in a manner corresponding to the load-versus-stroke correlation
of the same opening mechanism when it is built-in and tested under ambient temperature. It shall reach the
stroke that corresponds to the fire-open position of the ventilator in not more than 60 s.
8.4 Wind load
8.4.1 Wind-load classification
The ventilator shall be classified as one of the following:
a) WL 1 500;
b) WL 3 000;
c) WL A.
The designations 1 500, 3 000 and “A” represent the test wind-suction load, expressed in pascals, applied
when the ventilator is tested in accordance with Annex F.
8.4.2 Performance under wind load
The ventilator shall not open under the wind load appropriate to its classification, and shall not suffer
permanent deformation when tested in accordance with Annex F; following this test, it shall open into the
fire-open position within 60 s of actuation.
8.4.3 Resistance to wind-induced vibration
If wind deflectors form an integral part of the ventilator, their natural frequency of vibration shall be higher than
10 Hz with a logarithmic decrement of damping greater than 0,1 when tested in accordance with F.4.2.
8.5 Resistance to heat
8.5.1 Classification
The ventilator shall be classified as given under a) and/or b):
a) For a wall-mounted ventilator:
1) B 300,
Wall
2) B 600,
Wall
3) B A.
Wall
b) For roof-mounted ventilator:
1) B 300,
Roof
2) B 600,
Roof
3) B A.
Roof
The designations 300, 600 and “A” represent the temperature, expressed in degrees Celsius, at which the
ventilator is tested in accordance with Annex G.
8.5.2 Performance
8.5.2.1 The reaction to fire of the materials of the ventilator shall be tested and classified in accordance
with national requirements.
8.5.2.2 The throat area shall not be reduced by more than 10 % of the initial throat area when the
ventilator is tested in accordance with Annex G.
10 © ISO 2006 – All rights reserved

9 Evaluation of conformity
9.1 General
The compliance of natural smoke and heat ventilators with the requirements of this part of ISO 21927 shall be
demonstrated by
⎯ type testing;
⎯ factory production control by the manufacturer.
9.2 Type testing
Type testing, which shall be performed on first application of this part of ISO 21927, shall demonstrate
conformity with Clauses 5, 7 and 8, with the tests being carried out in the order specified in Clause 6.
Tests previously performed in accordance with the provisions of this part of ISO 21927 [same product, same
characteristic(s), test method, sampling procedure, system of attestation of conformity, etc.] may be taken into
account.
In addition, initial type testing shall be performed at the beginning of the production of a new product type or at
the beginning of a new method of production (where these may affect the stated properties).
9.3 Factory production control (FPC)
The manufacturer shall establish, document and maintain an FPC system to ensure that the products placed
on the market conform with the stated performance characteristic. The FPC system shall consist of
procedures, regular inspections and tests and/or assessments and the use of the results to control raw and
other incoming materials or components, equipment, the production process and the product, and shall be
sufficiently detailed to ensure that the conformity of the product is apparent.
An FPC system conforming with the requirements of ISO 9001, and made specific to the requirements of this
part of ISO 21927, shall be considered to satisfy the above requirements.
The results of inspections, tests or assessments requiring action shall be recorded, as shall any action taken.
The action to be taken when control values or criteria are not met shall be recorded.
10 Marking
The ventilator shall be marked with the following:
a) name or trade mark of the supplier and/or manufacturer;
b) type and model;
c) year of manufacture;
d) technical characteristics of the external energy supply (e.g. power, current, voltage, pressure); if integral
gas containers are used, they shall be marked with at least the following: mass and type of gas, fill ratio
and nominal temperature;
e) temperature of the thermal initiation device (if fitted);
f) aerodynamic free area (see B 2.5) in square metres;
g) classes for wind load, snow load, low ambient temperature, reliability and heat-exposure temperature if
provided;
h) number and year of this part of ISO 21927;
i) indication of suitability for wall mounting with wind-sensitive control system only (if tested to B.2.4.2).
11 Installation and maintenance information
11.1 Installation information
The supplier shall provide appropriate installation information for the following:
⎯ attachment;
⎯ connection to external services (e.g. electrical and pneumatic installation).
11.2 Maintenance information
The supplier shall provide appropriate maintenance information for the ventilator, which shall include the
following:
⎯ inspection and maintenance procedures;
⎯ recommended frequency of operational checks;
⎯ recommended checks for the effects of corrosion.
12 © ISO 2006 – All rights reserved

Annex A
(normative)
General testing procedures
A.1 Test sequence
For type approval testing, carry out the tests in the following sequence:
a) determination of the aerodynamic free area; see Annex B;
b) reliability test; see Annex C;
c) opening test under load; see Annex D;
d) low ambient temperature test; see Annex E;
e) wind load test; see Annex F;
f) heat exposure test; see Annex G.
The same ventilator shall be used for the reliability test (see Annex C) and opening under load test
(see Annex D).
A.2 Test report
A test report shall be prepared including the following:
⎯ name or trade mark and address of the supplier and/or manufacturer;
⎯ name of the product (type and model);
⎯ date(s) of the test(s);
⎯ name(s) and address(es) of the testing organization;
⎯ description of the test specimen;
⎯ reference to the test method(s);
⎯ conditions of test(s);
⎯ observations during the test(s);
⎯ test results;
⎯ classifications achieved, if relevant.
Annex B
(normative)
Determination of the aerodynamic free area
B.1 Simple assessment procedure
B.1.1 Roof-mounted ventilators
For the types of ventilator shown in Figure B.1 and that are in accordance with 5.4, the discharge coefficient
may be taken as C = 0,4 for installation situations with an upstand height of at least 300 mm and for the
v
specified opening angle. An inflow of air into the fire room instead of a discharge of smoke from the fire room
shall be avoided. Small opening angles and/or other installation situations, e.g. see Figure B.2, can lead to
negative discharge coefficients.
Dimensions in millimetres, unless otherwise noted

a
A equals length times width.
b
(α + β) = 140°.
max
Figure B.1 — Types of ventilator for the simple assessment procedure
14 © ISO 2006 – All rights reserved

Dimensions in millimetres, unless otherwise noted

a
A equals length times width.
b
(α + β) = 140°.
max
Figure B.1 (continued)
B.1.2 Wall-mounted ventilators
For the types of ventilators shown in Figure B.2 and that are in accordance with 5.4, the discharge coefficient
given in Table B.1 may be taken for the specified opening angles. An inflow of air into the fire room instead of
a discharge of smoke from the fire room shall be avoided. This can necessitate a wind-direction-dependent
opening of the ventilators.
a)  Opening to the outside b)  Opening to the inside
Figure B.2 — Examples of types of ventilator probably leading to negative discharge
The aerodynamic free area according to the simple assessment procedure shall be approved by a notified
testing station.
Tableau B.1 — Discharge coefficients for wall-mounted ventilators using the simple assessment
procedure for various opening angles, α
a
Coefficient
α
degrees
SHEV opening to the outside SHEV opening to the inside
30 0,25 0,20
45 0,30 0,25
60 0,40 0,30
90 0,50 0,40
a
If the height, x , as indicated in Figure B.2, b), is reduced to less then 0,5 m, then the values in this
h
table are not applicable and it is necessary that they be reconsidered accordingly.
B.2 Experimental procedure
B.2.1 General
Unless the simple assessment procedure of Clause B.1 is used, determine A experimentally, either directly or
a
indirectly from results on ventilators of different size or scaled-down models.
B.2.2 Test apparatus
Use a test apparatus with an open jet or a closed test-section facility calibrated in accordance with Clause B.3.
This consists of a settling chamber onto which the ventilator can be mounted in accordance with Figure B.4,
so that the mass flow through the ventilator can be determined, and a side-wind simulator by means of which
the ventilator can be subjected to a side wind. The flow in the settling chamber approaching the smoke
ventilator shall be steady state and uniform.
This can be achieved if the ratio, A /A , of the geometric area of the ventilator to the horizontal cross-
v sc
sectional area of the settling chamber is less than or equal to 0,15 and the velocity, V , measured in the open
sc
hole (without ventilator) at the points specified in Figure B.6 varies by only ± 10 % of the mean velocity, V ,
m,sc
of the settling chamber.
16 © ISO 2006 – All rights reserved

To obtain a uniform side-wind condition when the ventilator is subjected to side wind, the tests shall be carried
out in side-wind simulation facilities.
The following conditions for each facility shall be satisfied:
Table B.2 — Required conditions for tests in side-wind simulation facilities
Ratio Open-jet facilities Closed test-section facilities
A /A u 0,3 u 0,08
pr n
H /H W 1,3 W 3
n v
B /B W 1,5 W 2
n v
V , metres per second W 10 W 10
n
I , percent u 10 u 10
u, hUS
The following conditions shall be satisfied for both facilities.
The velocity, V , at mid-height of the upstand above the test-section floor shall meet the condition given in
hus/2
Equation (B.1):
0,85⋅ hus 2
()
where
VV++V+V
Hv
()Hv 2 ()3Hv 4 ()5Hv 4
V = (B.2)
subscript Hv represents the maximum height of the ventilator in the fire-open position.
None of the velocities measured at the points indicated in Figure B.6 in the entrance area to the test section,
for either the open jet or the closed test-section facilities, varies by more than ± 10 % of the mean nozzle
velocity, V .
n
NOTE Using larger side-wind velocities increases the accuracy of the measurements.
When using larger side-wind velocities, the discharge coefficient, c , shall be taken for the dimensionless
vw
pressure ratio, ∆p /p = 0,082.
int d
B.2.3 Test specimen
Carry out tests on full-size smoke ventilators as supplied by the manufacturer and/or supplier, or on accurately
scaled-down models. For testing, the similarity of flow characteristics of scaled-down models shall be
established. This is always achieved if the Reynolds number of the scaled-down model is identical to the full-
scale ventilator. To achieve the Reynolds number similarity usually requires model scales of 1:6 or larger.
Smaller scales (down to 1/10) may be used if justification is given for the flow similarity.
When testing scaled-down models, all features of the ventilators in contact with the airflow (e.g. opening
elements or details of flaps) shall be included and shall satisfy the similarity requirement.
NOTE Experience has shown that it is difficult to model ridge vents and louver type ventilators.
It is not considered necessary to test all sizes of a range of similar ventilators, provided tests are carried out
on a representative selection of sizes. For a range of similar ventilators consisting of eight or more sizes, at
least four sizes shall be investigated experimentally, two with a length-to-width ratio smaller than 1,5 and two
with a length-to-width ratio larger or equal 1,5. The sizes (at least eight) to be investigated for larger ranges
shall be chosen in such a way that the relative upstand height, which equals the upstand height, h , divided
US
by the hydraulic diameter, d , of the geometric opening, evenly covers the whole range of possible h /d
h,g US h,g
ratios. For small (fewer than eight) ranges, the smallest and the largest ventilator shall be investigated. For
testing ventilators differing in dimensions but belonging to the same range, A may be calculated for
a
intermediate sizes. The method of calculation shall be mentioned in the test report.
For ventilators designed as part of a continuous roof-light, the test specimen shall be mounted on the rig with
parts of the roof-lights. Those parts shall have a minimum width of half the external dimension of the ventilator
parallel to the line of the roof-light. For ventilators intended for use in continuous roof-lights, the gable ends of
the roof-light ends shall be streamlined or fitted with a deflection device as shown in Figure B.8.
B.2.4 Test procedure
B.2.4.1 Roof-mounted ventilators
Quantify the outside ambient static pressure with and without wind using the following procedure. Make sure
the settling chamber is airproof. Fit into the exit opening of the settling chamber and flush with the exterior of
the settling chamber ceiling a thin plate with evenly spaced holes with a diameter of 5 cm in order to get a
geometric porosity. The ratio of hole area to exit area of settling chamber equals to (5 ± 1) %. Measure the
static pressure in the settling chamber without wind, p , [Equation (B.3)] and with wind p
int,v0 int,vw
[Equation (B.4)] according to the side-wind conditions specified below with reference to the atmospheric
pressure, p :
amb
p = p + ∆p (B.3)
int,v0 amb,1 v0
p = p + ∆p (B.4)
int, vw amb,1 vw
Record the ∆p and ∆p values, remove the drilled plate, and fit the ventilator on the settling chamber. Carry
v0 vw
out the tests with and without wind.
For the no-side-wind case, set the full-scale ventilator onto the settling chamber to get the internal static
pressure, p , as given in Equation (B.5):
int
p = p + ∆p + ∆p (B.5)
int amb,2 v0 int
where
∆p ranges from 3 Pa to 12 Pa, with an accuracy of at least + 5 %;
int
p is the atmospheric pressure at the time of the measurement.
amb,2
Measure the ambient atmospheric pressure and temperature, the static pressure of the air in the settling
chamber and the volume flow entering the settling chamber. Determine for each value of ∆p the
int

corresponding mass flow m .
ing
Take at least six readings of ∆p and m for testing without side wind.
int ing
When testing scaled-down models at an increased pressure difference, ∆p , due to the requirement for the
int
similarity of Reynolds numbers, the accuracy required of measurement shall be + 3 % of the reading. The
required accuracy of the mass flow measurement is + 2,5 % of the reading. Measure the temperature and the
pressure of the ambient air with an accuracy of + 0,5 K and + 0,5 %, respectively.
To carry out tests on full-scale ventilators with a side-wind speed of 10 m/s upstream of the test section,
measure the atmospheric pressure and temperature of the air in the wind flow upstream of the test section.
Set the ventilator onto the settling chamber to get the internal static pressure, as given in Equation (B.6):
p = p + ∆p + ∆p (B.6)
int amb,3 vw int
18 © ISO 2006 – All rights reserved
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