ISO 21927-2:2018

INTERNATIONAL ISO
STANDARD 21927-2
Second edition
2018-11
Smoke and heat control systems —
Part 2:
Specifications 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 2018
© ISO 2018
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Published in Switzerland
ii © ISO 2018 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 4
5 Requirements . 5
5.1 Nominal activation conditions/sensitivity . 5
5.1.1 Initiation device . 5
5.1.2 Opening mechanism . 6
5.1.3 Inputs and outputs . 6
5.2 Response delay (response time) . 6
5.2.1 Reliability . 6
5.2.2 Opening under (snow/wind) load . 6
5.2.3 Low ambient temperature . 7
5.2.4 Opening under heat . 7
5.3 Operational reliability . 7
5.4 Effectiveness of smoke/hot gas extraction (aerodynamic free area) . 7
5.5 Performance parameters under fire conditions . 7
5.5.1 Resistance to heat . 7
5.5.2 Mechanical stability . 8
5.5.3 Reaction to fire . 8
5.6 Performance under environmental conditions. 8
5.6.1 Opening under load . 8
5.6.2 Low ambient temperature . 8
5.6.3 Stability under wind load . 8
5.6.4 Resistance to wind-induced vibration . 8
5.6.5 Resistance to heat . 8
5.7 Durability . 9
5.7.1 Response delay (response time) . 9
5.7.2 Operational reliability . 9
5.7.3 Performance parameters under fire conditions . 9
6 Testing, assessment and sampling methods. 9
7 Marking, labelling and packaging .10
Annex A (normative) Classification .12
Annex B (normative) Effectiveness of smoke/hot gas extraction (aerodynamic free area) .15
Annex C (normative) Test method for operational reliability and response time .38
Annex D (normative) Test method for opening under load .40
Annex E (normative) Test method for low ambient temperature .42
Annex F (normative) Test method for stability under wind load .43
Annex G (normative) Test method for resistance to heat .45
Annex H (normative) Mounting and fixing conditions for the SBI or small flame tests .56
Annex I (normative) Handling changes affecting declared performances for NSHEV .59
Annex J (informative) Installation and maintenance information .62
Bibliography .63
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.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/directives).
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. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www .iso
.org/iso/foreword .html.
This document 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.
This second edition cancels and replaces the first edition (ISO 21927-2:2006), which has been technically
revised. It also incorporates the Amendment ISO 21927-2:2006/Amd1: 2010.
The main changes compared to the previous edition are as follows:
— the test apparatus has been amended;
— the whole document has been revised.
A list of all parts in the ISO 21927 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/members .html.
iv © ISO 2018 – 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 firefighting 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 natural
smoke and heat exhaust ventilators (referred to in this document as NSHEV) 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 document as a SHEVS) is a system of safety equipment intended to perform a positive
role in a fire emergency.
INTERNATIONAL STANDARD ISO 21927-2:2018(E)
Smoke and heat control systems —
Part 2:
Specifications for natural smoke and heat exhaust
ventilators
1 Scope
This document applies to natural smoke and heat exhaust ventilators (NSHEV) operating as part of
smoke and heat exhaust systems (SHEVS), placed on the market. This document specifies requirements
and gives test methods for natural smoke and heat exhaust ventilators which are intended to be
installed in smoke and heat control systems in buildings.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 11925-2, Reaction to fire tests — Ignitability of products subjected to direct impingement of flame —
Part 2: Single-flame source test
ISO 21927-9, Smoke and heat control systems — Part 9: Specification for control equipment
ISO 21927-10, Smoke and heat control systems — Part 10: Specification for power output devices
IEC 60584-1, Thermocouples — Part 1: EMF specifications and tolerances
EN 54-5, Fire detection and fire alarm systems — Part 5: Heat detectors — Point detectors
EN 54-7, Fire detection and fire alarm systems — Part 7: Smoke detectors — Point detectors using scattered
light, transmitted light or ionization
EN 13501-1, Fire classification of construction products and building elements — Part 1: Classification
using test data from reaction to fire tests
EN 13823, Reaction to fire tests for building products — Building products excluding floorings exposed to
the thermal attack by a single burning item
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at https: //www .electropedia .org/
— ISO Online browsing platform: available at https: //www .iso .org/obp
3.1
aerodynamic free area
A
a
measure of smoke and heat exhaust area of the ventilator
Note 1 to entry: It is the geometric area multiplied by the coefficient of discharge.
3.2
ambient
relating to the properties of the surroundings
3.3
automatic initiation
activation of operation without direct human intervention
3.4
aspect ratio
ratio of length to width
3.5
comfort ventilation position
position of a NSHEV defined by the manufacturer for the purpose of comfort ventilation
3.6
coefficient of discharge
c
v
ratio of actual flow rate, measured under specified conditions, to the theoretical flow rate through the
NSHEV, as defined in Annex B
Note 1 to entry: The coefficient takes into account any obstructions in the NSHEV such as controls, louvres and
vanes and the effect of external side wind.
3.7
dual purpose NSHEV
NSHEV which has provision to allow its use for comfort (i.e. day to day) ventilation
3.8
fire open position
configuration of the NSHEV specified by its designer to be achieved and sustained while venting smoke
and heat
3.9
gas container
vessel containing gas in a compressed form, the energy of which, when the gas is released from the
vessel, will open the NSHEV
3.10
geometric area
A
v
area of the opening through a NSHEV, measured in the plane defined by the surface of the construction
works, where it contacts the structure of the NSHEV
Note 1 to entry: No reduction is made for controls, louvres or other obstructions.
Note 2 to entry: Specific configurations are given in Figures B.1 and B.4.
3.11
initiation device
device which activates the operating mechanism of the NSHEV on receipt of information from a fire
detection system or thermal device
2 © ISO 2018 – All rights reserved

3.12
opening mechanism
mechanical device which operates the NSHEV to the fire open position
3.13
projection area
cross-sectional area of the movable part (e.g. flap, window) of the NSHEV:
a) above the plane of the roof, at a right angle to the side wind flow;
b) on the wall at a right angle to the side of the wall
3.14
range
NSHEV of various sizes having the same method of construction and the same type of opening
mechanism
3.15
natural smoke and heat exhaust ventilator
NSHEV
product specially designed to move smoke and hot gases out of a construction works naturally under
conditions of fire
Note 1 to entry: In the context of this document, smoke and hot gas movement means any motion of smoke and
hot gas within and out of a construction work under the influence of thermal buoyancy, e.g. exhausting and
extracting smoke and hot gas, directing and guiding smoke and hot gas.
Note 2 to entry: A typical NSHEV consists of a fixed frame or upstand and of one or more flaps to be opened in
case of fire by an opening mechanism initiated by a smoke or heat sensitive initiation device.
3.16
thermal device
temperature-sensitive device which responds to initiate a subsequent action
3.17
throat area
smallest cross-sectional area of the flow path through the NSHEV
Note 1 to entry: See Figure G.6.
3.18
ventilator
device for enabling the movement of gases into or out of the construction works
3.19
wind deflector
any part of the NSHEV guiding the wind over the open NSHEV
3.20
wind-sensitive control system
control system designed to control two or more banks of NSHEV on separate elevations so that only the
NSHEV not subject to positive wind pressures opens in case of fire
3.21
wall
external building surface with an inclination of more than 60° relative to the horizontal
3.22
roof
external building surface with an inclination of 60° or less relative to the horizontal shed roofs, and
which continuous roof-lights, independent of the inclination angle
4 Symbols and abbreviated terms
For the purposes of this document, mathematical and physical quantities are represented by symbols,
and expressed in units as follows.
Symbol Definition Unit
A aerodynamic free area, expressed in square metres m
a
A area of the exit plane of NSHEV, expressed in square metres m
ex
A nozzle exit area (for open jet facilities); test section entrance area (for closed m
n
test section facilities), expressed in square metres
A projection area of the NSHEV for the side wind flow, expressed in square m
pr
metres
A horizontal cross section area of the settling chamber, expressed in square m
sc
metres
A smallest geometric cross section area through which the air flows m
throat
A geometric area of the NSHEV, expressed in square metres m
v
B width of the open hole of the settling chamber, expressed in metres m
b width of the geometric opening of a NSHEV, expressed in metres m
B width of nozzle exit area in open jet facilities, width of the test section in m
n
closed test section facilities, expressed in metres
B maximum width of the NSHEV in the fire open position, expressed in metres m
v
above 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
d hydraulic diameter of the settling chamber [d = (4 · A ) / P], expressed in m
h h sc
metres
d hydraulic diameter of the geometric NSHEV area, expressed in metres m
h,g
H height of nozzle exit area in open jet facilities, height of the test section in m
n
closed test section facilities, expressed in metres
H maximum height of the NSHEV in the fire open position above the upper sur- m
v
face of the settling chamber, expressed in metres
h profile height of a wall-mounted NSHEV, expressed in metres m
p
h height of the NSHEV upstand, expressed in metres m
us
h height of the upper edge of wind deflectors above the roof surface, expressed m
uwd
in metres
L length of the open hole of the settling chamber, expressed in metres m
l length of the geometric opening of a NSHEV, expressed in metres m
I turbulence intensity in flow direction at height h —
u, hUS US
m ratio of geometric areas (= A / A ), dimensionless —
ex v
mass flow rate entering the settling chamber, expressed in kilograms per kg/s

m
ing
second
NSHEV natural smoke and heat exhaust ventilator —
P perimeter length of the cross section of the settling chamber, expressed in m
metres
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 2018 – All rights reserved

Symbol Definition Unit
T temperature, expressed in degrees C °C
U length of the boundary of the geometric area of a NSHEV, expressed in metres m
v
V side wind velocity, expressed in metres per second m/s
∞
V local air speed, expressed in metres per second m/s
l
V mean velocity of the settling chamber, expressed in metres per second m/s
m, sc
V mean nozzle velocity, expressed in metres per second m/s
n
V local velocities in plane above settling chamber, see Figure B.6, expressed in m/s
sc
metres per second
α opening angle of the NSHEV, expressed in degrees and referenced to the —
closed flap position
β angle of attack, expressed in degrees —
β incidence angle at which the smallest value of C obtained with side wind, —
crit vw
occurs, expressed in degrees
δ relative wall thickness (= h / d ), dimensionless —
US h
δ relative profile thickness (= h / d ) of a wall-mounted NSHEV, dimensionless —
p p h
µ contraction coefficient (= A / A ), dimensionless —
a ex
θ angle of installation of NSHEV on a roof or in a wall, expressed in degrees —
Δp pressure difference, expressed in Pascals Pa
Δp reference pressure difference between the static pressure in the settling Pa
v0
chamber and the ambient pressure without side wind, expressed in Pascals
Δp reference pressure difference between the static pressure in the settling Pa
vw
chamber and the ambient pressure with side wind, expressed in Pascals
Δp pressure difference between the static pressure in the settling chamber and Pa
int
the ambient pressure, expressed in Pascals
ΔT temperature difference, expressed in Kelvins K
ρ density of air, expressed in kilograms per cubic metre kg/m
air
5 Requirements
5.1 Nominal activation conditions/sensitivity
5.1.1 Initiation device
5.1.1.1 General
To ensure the natural smoke and heat exhaust ventilator (NSHEV) opens in the event of a fire, it shall be
fitted with one or more of the following automatic initiation devices:
a) a thermal initiation device;
b) an initiation device activated by an electrical signal from a remote source, e.g. a smoke and heat
detector system, the interruption of electrical power supply;
c) a pneumatic initiation device, e.g. a pneumatic signal or a loss of compressed air;
d) an initiation device able to respond to other types of release signals.
In addition, remote initiation can take place by means of a manually operated initiation device.
e) A pneumatic non fail safe NSHEV, which does not open automatically on loss of power, shall have at
least a thermal device and one power source in accordance with ISO 21927-10, which is mounted
directly in the NSHEV, unless the required control panel monitors the lines to the NSHEV and
indicates a failure.
In some specific design cases where it is suitable to initiate the NSHEV manually only, the NSHEV may
be installed without an automatic initiation device.
5.1.1.2 Automatic initiation or release device
Any automatic initiation or release device shall be within the NSHEV and shall be exposed to the hot gas
entering the closed NSHEV.
There are two exceptions to this requirement, where an automatic thermal initiation or release device
shall not be fitted to the NSHEV.
a) If the NSHEV is to be installed as a wall-mounted NSHEV. Adverse wind conditions may cause a NSHEV
which has been opened by the automatic initiation device to inlet and not remove heat and smoke.
b) In specific design cases where it is suitable that the NSHEV shall only be manually initiated. The
response behaviour of thermal automatic initiation devices shall be in accordance with ISO 21927-9.
Smoke detectors shall comply with the requirements of EN 54-7 and heat detectors with EN 54-5.
5.1.2 Opening mechanism
5.1.2.1 General
The NSHEV shall be provided with an opening mechanism with energy within the NSHEV, e.g. gas
containers, spring systems, electrical power supply, and/or with an external energy source. For
the external links, the manufacturer of the NSHEV shall specify the operating requirements for the
initiation device and the opening mechanism, e.g. voltage, energy.
5.1.2.2 Integral gas containers
Any gas container forming an integral part of the NSHEV shall be equipped with a pressure release
device to prevent an explosion if the container overheats. The energy supply shall comply with
ISO 21927-10.
5.1.3 Inputs and outputs
If the NSHEV is intended to operate with an external energy source, it shall be equipped with inputs
and/or outputs to allow connection of the NSHEV to the control panel and power supplies in accordance
with ISO 21927-10.
5.2 Response delay (response time)
5.2.1 Reliability
The NSHEV shall when tested in accordance with Annex C open, i.e. reach its fire open position, within
60 s after actuation.
5.2.2 Opening under (snow/wind) load
Roof mounted NSHEV 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.
After testing the NSHEV in accordance with Annex F it shall open into the fire open position within 60 s
after actuation.
6 © ISO 2018 – All rights reserved

5.2.3 Low ambient temperature
When tested in accordance with Annex E the NSHEV shall open into to the fire open position within
60 s after actuation.
5.2.4 Opening under heat
The NSHEV shall when tested in accordance with Annex G open, i.e. reach its fire open position within
60 s under exposure to heat and to remain in the fire open position with not more than 10 % reduction
of the throat area.
5.3 Operational reliability
The NSHEV shall when tested in accordance with Annex C open, i.e. reach its fire open position, within
60 s after actuation without damage and remain in its fire open position without an external energy
supply (until reset).
5.4 Effectiveness of smoke/hot gas extraction (aerodynamic free area)
The aerodynamic free area, A , of the NSHEV shall be determined in accordance with Annex B.
a
Roof mounted NSHEV shall be tested without and with side wind. Wall-mounted NSHEV may be tested
without side wind only.
In order to prevent air from flowing through the NSHEV into the fire room the aerodynamic free area,
A , shall be larger than 0 m .
a
Wind deflectors subjected to atmospheric wind when the NSHEV is in the closed position and forming
an integral part of the NSHEV to ensure the determined aerodynamic free area, A , shall be tested in
a
accordance with 5.6.4.
Devices having influence on the aerodynamic performance are integral parts of the NSHEV and shall
be installed in accordance with the manufacturer’s instructions and shall be tested in accordance with
Annex B, whether they are fixed to the NSHEV itself or to the surrounding construction.
When using the simple assessment procedure to determine the aerodynamic free area, see B.1. The side
length shall not exceed 2,5 m and the aspect ratio of the geometric area shall not exceed 5:1.
Large area NSHEV may lead to plug holing, i.e. exhaust flows where smoke from the smoke layer and
room air are mixed and removed and therefore the removal of smoke is decreased.
5.5 Performance parameters under fire conditions
5.5.1 Resistance to heat
The NSHEV shall open within 60 s under exposure to heat and remain in the fire open position without
an external energy supply with not more than 10 % reduction of the throat area when tested in
accordance with Annex G.
If the NSHEV shall be installed in a building, it shall have a minimum class B 30.
For NSHEV larger than the largest NSHEV 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.
NOTE At present, maximum dimensions of the test apparatus for the heat exposure test are in the range of 4 m.
5.5.2 Mechanical stability
The reduction of the throat area shall not be more than 10 % reduction when tested in accordance with
Annex G.
No part or component of the NSHEV shall fall from the NSHEV during the first 6 min of the test.
Devices having influence on the aerodynamic performance are integral parts of the NSHEV and shall
be installed in accordance with the manufacturer’s instructions and shall be tested in accordance with
Annex G whether they are fixed to the NSHEV itself or to the surrounding construction.
5.5.3 Reaction to fire
The reaction to fire shall be classified in accordance with A.5 and tested in accordance with Annex H.
5.6 Performance under environmental conditions
5.6.1 Opening under load
To simulate the side wind influence, the roof-mounted NSHEV shall be subjected, in the most
unfavourable wind direction, to a side wind of 10 m/s velocity when tested in accordance with Annex D.
Roof mounted NSHEV shall open, reach its fire open position within 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 NSHEV fitted with wind deflectors, the deflectors shall not be fitted in such a way to encourage
snow or ice to collect to the detriment of the operation of the NSHEV.
5.6.2 Low ambient temperature
When tested in accordance with Annex E, the NSHEV shall open into to the fire open position within
60 s after actuation. No such test is necessary for NSHEV classified T(05), see A.6.
Tests shall be conducted with simulated snow load with the classification in accordance with A.6.
5.6.3 Stability under wind load
The NSHEV shall not open at the opening side(s) more than 50 mm (measured at the location of the
actuator) under the wind load appropriate to its classification, see A.6. It shall also not suffer permanent
deformation when tested in accordance with Annex F and, following this test, shall open into the fire
open position within 60 s after actuation.
5.6.4 Resistance to wind-induced vibration
If wind deflectors form an integral part of the NSHEV, 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.5.2.
5.6.5 Resistance to heat
The NSHEV shall open within 60 s under exposure to heat and remain in the fire open position with not
more than 10 % reduction of the throat area when tested in accordance with Annex G.
If the NSHEV shall be installed in a building it shall have a minimum class B 30.
8 © ISO 2018 – All rights reserved

5.7 Durability
5.7.1 Response delay (response time)
The durability of NSHEV considering response delay is fulfilled if the fire open position is reached
within 60 s after being tested at least 49 times in accordance with Annex C.
5.7.2 Operational reliability
The durability of NSHEV considering operational reliability is fulfilled if the fire open position is
reached after being tested at least 49 times in accordance with Annex C.
5.7.3 Performance parameters under fire conditions
The NSHEV is regarded to be durable if, after the test in accordance with Annex G, the throat area is not
reduced by more than 10 % and all parts relevant for the aerodynamic performance of the NSHEV, e.g.
filling, wind deflectors and flaps and all structural parts, remain in place.
6 Testing, assessment and sampling methods
Test of NSHEV shall be carried out in accordance with Annexes B, C, D, E, F, G and H.
For each test, a test report shall be prepared.
The methods for testing, assessing and sampling for the essential requirements of Clause 5 are:
— For the “nominal activation condition/sensitivity”, the presence of the initiation device according to
5.1.1, the “opening mechanism” according to 5.1.2 and “inputs and outputs” according to 5.1.3 shall
be checked as present.
— The “response delay (response time)” shall be less than ≤60 s. It shall be tested for reliability
according to Annex C, for opening under (snow/wind) load according to Annex D and F, for low
ambient temperature according to Annex E and for opening under heat according to Annex G and
assessed in accordance with Annex A. The sampling methods are given in Annexes C, D, E, F, and G.
— The operational reliability shall be tested in accordance with Annex C and assessed in accordance
with Annex A. The sampling method is given in Annex C.
Table 1
Number of openings into the
Reliability classes
fire open position
Re 50 50
Re 500 500
Re 1000 1 000
Re A A
— The effectiveness of smoke/heat gas extraction — aerodynamic free area shall be tested and
assessed in accordance with Annex B. The aerodynamic free area, A , shall be larger than 0 m . The
a
sampling method is given in Annex B.
— The performance parameters under fire conditions, resistance to heat and mechanical stability
shall be tested and assessed in accordance with Annex G with A as:
B 30,
B 30,
B 30.
A
and reaction to fire in accordance with Annex H with A as:
class
The sampling methods are given in Annexes G and H.
— The performance under environmental conditions shall be tested and assessed for the performance
under load in accordance with Annex D with A as:
Table 2
Load
Snow load
Pa
SL 500 500
SL 1000 1 000
SL 1500 1 500
SL A A
for the stability under wind load in accordance with Annex F with A as:
Table 3
Load
Wind load
Pa
WL 1500 1 500
WL 3000 3 000
WL A A
for the low ambient temperature in accordance with Annex E with A as:
T(−25),
T(−15),
T(−05),
T(05),
T A.
and for the resistance to wind induced vibrations in accordance with Annex F with A as:
— natural frequency of vibration, ω : >10 Hz;
— logarithmic decrement of damping, δ: >0,1.
The sampling methods are given in Annexes D, E, and F.
Tests for reliability conducted in accordance to Annex C and for resistance to heat in accordance to
Annex G are considered to satisfy the requirements of durability as specified in 5.7.1, 5.7.2 and 5.7.3.
7 Marking, labelling and packaging
The manufacturer shall give on each NSHEV the information in accordance with list entries a) to k):
a) the name or trade mark of the manufacturer;
10 © ISO 2018 – All rights reserved

b) the type and model;
c) the year of manufacture (this may be in coded form);
d) technical characteristics of the external energy supply (e.g. power, current, voltage, pressure), type
of opening (see 5.1.2); if integral gas containers are used they shall be marked with at least the
following: mass and type of gas, fill ratio, nominal temperature;
e) the temperature of the thermal initiation device (if fitted);
f) the aerodynamic free area (see B.3.5) in square metres and limitations to application if relevant
(e.g. wind direction dependent opening, with or without wind deflector, additional aerodynamic
device);
g) the classes for wind load, snow-load, low ambient temperature, reliability, heat exposure
temperature and reaction to fire;
h) a reference to this document and its year of publication, i.e. ISO 21927-2:2018;
i) suitable for wall-mounted ventilator: with wind-sensitive control system only (if tested in
accordance with B.3.4.2);
j) the range of installation angle relative to the horizontal; and
k) dual purpose NSHEV, if relevant.
NSHEV delivered to site in a form of components shall be reassembled under the responsibility of the
manufacturer. No cutting, drilling, milling or welding of these components are allowed for reassembling.
The manufacturer shall take into account that packaging, handling and storage conditions do not have
any negative influences on the declared performances of the NSHEV.
Packaging should be done in such a way that the NSHEV has its declared performance after delivery.
Annex A
(normative)
Classification
NOTE See Clause 4.
A.1 Nominal activation condition/sensitivity
For the “nominal activation condition/sensitivity”, the presence of the initiation device according to
5.1.1, the “opening mechanism” according to 5.1.2 and “inputs and outputs” according to 5.1.3 shall be
visually checked and described as present.
A.2 Response delay
The “response delay (response time)” shall be less than or equal to 60 s. It shall be tested for:
— reliability according to Annex C;
— opening under (snow/wind) load according to Annex D and F;
— low ambient temperature according to Annex E; and
— opening under heat according to Annex G.
It shall also be assessed in accordance with Annex A. and described as less than or equal to 60 s.
A.3 Operational reliability
The NSHEV shall be classified as one of the following classes:
— Re 50;
— Re 1000;
— Re A.
The designation 50, 1000 and A in the above-mentioned classes represent the number of openings into
the fire open position and closing under no applied load in accordance with Annex C.
A.4 Effectiveness of smoke/hot gas extraction (aerodynamic free area)
The effectiveness of smoke/heat gas extraction — aerodynamic free area shall be tested and assessed
in accordance with Annex B. The aerodynamic free area A shall be larger than 0 m .
a
A.5 Performance parameters under fire conditions
The resistance to heat and the mechanical stability in accordance with Annex G shall be classified as:
— B 30;
— B 30;
— B 30;
A
12 © ISO 2018 – All rights reserved

and reaction to fire in accordance with Annex H as:
— class.
The designations 300, 600 and A in the above-mentioned classes represent the temperature (in °C) at
which the NSHEV is tested in accordance with Annex G.
A.6 Performance under environmental conditions
The performance under load in accordance with Annex D shall be classified as:
— SL 500;
— SL 1000;
— SL 1500;
— SL A.
The designations 500, 1000, 1500 and A in the above-mentioned classes represent the test snow load
in Pa acting on the projection surface of the opening element(s) normal to the exit plane of the NSHEV,
applied when the NSHEV is tested in accordance with Annex D.
A NSHEV classified SL 0 can be installed in accordance with the manufacturer’s instructions with a
minimum angle of installation wider than 45° (combining roof pitch and vent pitch, see Figure A.1,
except where the snow is prevented from slipping from the NSHEV, for example, by wind deflectors).
Except for SL 0 for NSHEV fitted with three or four sided deflectors, the snow load classification should
not be less than SL = 2 000 × d, where d is the depth of snow, in metres, which can be contained within
the confines of the deflectors.
It is recommended that louvre-type NSHEV are classified not less than SL 500 when used in sub-zero
temperature conditions.
Key
1 NSHEV
2 roof
Figure A.1 — Combined roof pitch and NSHEV pitch angle >45°
The stability under wind load in accordance with Annex F shall be classified as:
— WL 1500;
— WL 3000;
— WL A.
The designations 1500, 3000 and A in the above-mentioned classes represent the test wind suction load
in Pa for NSHEV opening outwards or the test wind pressure load in Pa for NSHEV opening inwards
acting on the area given as the product of the external dimensions of the opening element(s) when the
NSHEV is tested in accordance with Annex F.
The low ambient temperature in accordance with Annex E shall be classified as:
— T(−25);
— T(−15);
— T(−05);
— T(05);
— T A.
The designations −25, −15, −05, 05 and A in the above-mentioned classes represent the number of °C at
which the NSHEV is tested in accordance with Annex E.
Class T(05) NSHEV are only regarded as suitable for use in construction works where the room
temperature in the room underneath the NSHEV is 5 °C or above.
The resistance to wind induced vibrations of the wind deflectors tested in accordance with Annex F
shall be given as:
— natural frequency of vibration, ω : >10 Hz;
— logarithmic decrement of damping, δ: >0,1.
A.7 Durability
A.7.1 Response delay (response time)
The durability regarding response delay shall be given as ≤60 s after being tested at least 49 times in
accordance with Annex C.
A.7.2 Operational reliability
The durability regarding operational reliability shall be given as number of opening into the fire open
position tested at least 49 times in accordance with Annex C.
A.7.3 Performance parameters under fire conditions
The durability regarding the performance parameters under fire conditions after being tested in
accordance with Annex G shall be given as ΔA < 10 %.
throat
14 © ISO 2018 – All rights reserved

Annex B
(normative)
Effectiveness of smoke/hot gas extraction (aerodynamic free area)
NOTE See 5.4 and G.1.
B.1 Determination of the aerodynamic free area
The determination of the aerodynamic free area shall be determined according to the simple assessment
procedure or according to the experimental procedure.
B.2 Simple assessment procedure
B.2.1 General
The aerodynamic free area in accordance with the simple assessment procedure shall be determined
only by a notified testing laboratory.
B.2.2 Roof mounted NSHEV
For the types of NSHEV shown in Figure B.1 a) and with dimensions in accordance with 5.4, the
discharge coefficient may be taken as C = 0,4 for installation situations with an upstand height of at
v
least 300 mm and for the opening angle specified in Figure B.1 a). 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, may lead to negative
discharge coefficients.
This may necessitate a wind direction dependent opening of the NSHEV.
B.2.3 Wall-mounted NSHEV
For the types of NSHEV shown in Figure B.1 b) and the dimensions of which are in accordance with
5.4 the discharge coefficient in the no-wind condition given in Table B.1 may be taken for the opening
angles s
...