ISO 21927-6

Smoke and heat control systems - Part 6: Specification for pressure differential systems

Systèmes pour le contrôle des fumées et de la chaleur — Partie 6: Spécifications relatives aux systèmes à différentiel de pression

General Information

• Status: Not Published
• ICS: 13.220.20 - Fire protection
• Technical Committee: ISO/TC 21/SC 11 - Smoke and heat control systems and components
• Drafting Committee: ISO/TC 21/SC 11 - Smoke and heat control systems and components
• Current Stage: 6000 - International Standard under publication
• Start Date: 15-Nov-2025
• Completion Date: 27-Dec-2025

Relations

• Parent: ISO 20701:2017 - Leather - Tests for colour fastness - Colour fastness to saliva
• Effective Date: 20-Apr-2024

Overview

ISO 21927-6:2025 specifies requirements for pressure differential systems (PDS) used in smoke and heat control. This standard is part 6 of the ISO 21927 series, dealing specifically with the specification, performance characteristics, and test methods for pressure differential system kits and components. The purpose of these systems is to maintain safe, smoke-free conditions in protected spaces such as staircases, lobbies, firefighting access routes, and escape routes during a fire event by establishing controlled pressure differences.

Pressure differential systems work by creating a higher pressure in protected areas relative to adjacent unprotected spaces. This pressure gradient prevents smoke from spreading, ensuring safe evacuation routes and access for firefighters.

Key Topics

• Pressure Differential System Function
  The PDS maintains a pressure gradient and airflow between protected spaces and unprotected fire compartments to prevent smoke ingress. The system achieves this by supplying air to the protected area and allowing controlled air release to balance pressure without smoke penetration.

• System Components
  Pressure differential systems typically include:

  • Temperature-rated fans (supply and exhaust)
  • Air and smoke control ducts
  • Ventilation openings and dampers (active or passive)
  • Control panels and pressure controllers
  • Power supply and cabling
  • Smoke control dampers and door closers

• Performance Characteristics
  The standard mandates key performance parameters such as:

  • Activation sensitivity: The nominal activation conditions for system engagement
  • Response time: Delay between activation signal and pressure establishment
  • Operational reliability: Consistent system function throughout fire events
  • Pressurization and air release effectiveness: Ability to maintain required pressure differentials and airflow to avoid unwanted pressure build-up
  • Fire resistance classifications: Integrity, insulation, smoke leakage limitation, mechanical stability, and durability of system components under fire conditions

• Test Methods and Verification
  ISO 21927-6 outlines extensive test methods including:

  • Measuring volume flow rates through air release paths and temporary openings
  • Response and activation testing under simulated fire conditions
  • Fire resistance tests based on international fire standards
  • Factory production control procedures and type testing for conformity assurance

• Terminology and Symbols
  The document harmonizes terminology with ISO 13943 (Fire safety vocabulary) and defines specific terms such as air release, pressurization, depressurization, active control, and pressure differential system (PDS). Symbols related to airflow rates, pressure differentials, and leakage values are standardized for clarity in specifications and testing.

Applications

Pressure differential systems specified by ISO 21927-6 find critical use in various building and infrastructure contexts where smoke control is vital during fires:

• Escape Routes & Stairwells
  Ensures smoke does not enter corridors or stairwells used for evacuation, maintaining breathable conditions.

• Firefighter Access Routes & Shafts
  Maintains clear pathways and lift shafts to facilitate firefighting operations.

• Lobbies and Protected Spaces
  Controls smoke ingress into protected zones to safeguard occupants and critical equipment.

• Commercial, Residential, and Public Buildings
  Applies broadly in offices, hospitals, schools, airports, and high-rise buildings to comply with fire safety regulations.

• Industrial Facilities
  Integrates with process safety to prevent smoke spread in hazardous areas.

By adhering to ISO 21927-6 requirements, building designers, fire safety engineers, and system installers can ensure that pressure differential systems are reliable, effective, and compliant with international fire safety standards.

Related Standards

ISO 21927-6 is part of the broader ISO 21927 series covering smoke and heat control systems:

• ISO 21927-2: Specifications for natural smoke and heat exhaust ventilators
• ISO 21927-3: Specifications for powered smoke and heat exhaust ventilators
• ISO 21927-7: Smoke duct sections specifications
• ISO 21927-8: Smoke control dampers specifications

Additional referenced standards include:

• ISO 13943: Fire safety vocabulary
• EN 1363-1: Fire resistance test general requirements
• EN 13501-4: Fire classification of construction products and building components relevant to smoke control systems

Together, these standards harmonize requirements and testing across smoke and heat control system components, supporting comprehensive fire safety strategies in building design and operation.

---

Implementing pressure differential systems according to ISO 21927-6 enhances smoke management and fire protection, safeguarding life and property through scientifically validated performance and rigorously tested components. For detailed design, installation, and maintenance, refer to this standard alongside other parts of the ISO 21927 series.

Standards Content (Sample)

International
Standard
First edition
Smoke and heat control systems —
Part 6:
Specification for pressure
differential systems
Systèmes pour le contrôle des fumées et de la chaleur —
Partie 6: Spécifications relatives aux systèmes à différentiel de
pression
PROOF/ÉPREUVE
Reference number
© ISO 2025
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
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CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
PROOF/ÉPREUVE
ii
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms, definitions, symbols and abbreviated terms . 1
3.1 Terms, definitions and abbreviated terms .1
3.2 Symbols .2
4 Characteristics . 3
4.1 General .3
4.2 Nominal activation conditions/sensitivity .4
4.2.1 Kit .4
4.2.2 Components .4
4.3 Response delay (response time) .5
4.3.1 Kit .5
4.3.2 Components .6
4.4 Operational reliability .6
4.4.1 Kit . .6
4.4.2 Components .7
4.5 Effectiveness of smoke/hot gas extraction (air release/powered air release) .7
4.5.1 Kit .7
4.5.2 Components .7
4.6 Performance parameters under fire conditions .8
4.6.1 Kit .8
4.6.2 Components .8
4.7 Pressurization performance .9
4.7.1 Kit .9
4.7.2 Components .9
4.8 Fire resistance – Integrity (E) .10
4.8.1 Kit .10
4.8.2 Components .10
4.9 Fire resistance – Insulation (I) .11
4.9.1 Kit .11
4.9.2 Components .11
4.10 Fire resistance – Smoke leakage (S) .11
4.10.1 Kit . .11
4.10.2 Components . 12
4.11 Fire resistance – Mechanical stability . 12
4.11.1 Kit . 12
4.11.2 Components . 12
4.12 Fire resistance – Maintenance of cross section. 13
4.12.1 Kit . . 13
4.12.2 Components . 13
4.13 Durability .14
4.13.1 Kit .14
4.13.2 Components .14
5 Test methods .15
5.1 General . 15
5.1.1 Kits . 15
5.1.2 Families . 15
5.1.3 Substitution of components from different families .16
5.2 Nominal activation conditions/sensitivity .16
5.2.1 Kit . .16
5.2.2 Components .16
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iii
5.3 Response delay (response time) .17
5.3.1 Kit .17
5.3.2 Components .17
5.4 Operational reliability .17
5.4.1 Kit .17
5.4.2 Components . 29
5.5 Effectiveness of smoke/hot gas extraction . 29
5.5.1 Kit . . 29
5.5.2 Components . 29
5.6 Performance parameters under fire conditions . 30
5.6.1 Kit . . 30
5.6.2 Components . 30
5.7 Pressurization performance .31
5.7.1 Kit . .31
5.7.2 Components .31
5.8 Fire resistance – Integrity (E) .31
5.8.1 Kit . .31
5.8.2 Components .32
5.9 Fire resistance – Insulation (I) .32
5.9.1 Kit . .32
5.9.2 Components .32
5.10 Fire resistance – Smoke leakage (S) . 33
5.10.1 Kit . . 33
5.10.2 Components . 33
5.11 Fire resistance – Mechanical stability . 34
5.11.1 Kit . . 34
5.11.2 Components . 34
5.12 Fire resistance – Maintenance of cross section. 34
5.12.1 Kit . 34
5.12.2 Components . 34
5.13 Durability . 35
5.13.1 Kit . . 35
5.13.2 Components . 35
6 Verification of performance .36
6.1 Type testing . 36
6.1.1 General . 36
6.1.2 Test samples, testing and compliance criteria . 36
6.1.3 Test reports .37
6.2 Factory production control (FPC) .37
6.2.1 General .37
6.2.2 Requirements . 38
6.2.3 Product specific requirements . 40
7 Marking, labelling and packaging .40
Annex A (normative) Pressure differential kit types (pressurization) .42
Annex B (normative) Test method for hot gas control damper at elevated temperature .53
Annex C (normative) Test required for powered smoke and heat exhaust ventilators with
frequency inverter and operated with variable speed at elevated temperature .57
Annex D (normative) Installation and maintenance document.59
Bibliography .60
PROOF/ÉPREUVE
iv
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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
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 the European Committee for Standardization (CEN) (as EN 12101-6:2022)
and was adopted, without modification other than those given below by Technical Committee ISO/TC 21,
Equipment for fire protection and fire fighting, Subcommittee SC 11, Smoke and heat control systems and
components.
— Editorial changes in 3.2, Symbols: the subscript elements are not written in italics.
— Normative references: the normative references were changed from the European Standard of the series
EN 12101-xx into the ISO standard of the series ISO 21927-xx.
— Clause 7: Headline "Table 3" was added and the sentence above the table was rephrased.
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.
PROOF/ÉPREUVE
v
Introduction
0.1  Objectives of pressure differential systems
Pressure differential systems offer the facility of maintaining tenable conditions in protected spaces, for
example: escape routes, firefighting access routes, firefighting lift shafts, lobbies, staircases, and other
spaces that require being kept free of smoke. It is necessary to determine not only where the fresh air
supply for pressurization is to be introduced into a building, but also where that air and smoke will leave the
building and what paths it will follow in the process.
The aim therefore is to establish a pressure gradient from the protected space to the unprotected space (fire
room) while the doors are closed, and an airflow while the doors are open.
0.2  Smoke control methods
The effect of the air movement forces, described above, are to create pressure differentials across the
partitions, walls and floors and can cause smoke to spread to spaces remote from the fire source. The
technique most commonly used to limit the degree of smoke spread, or to control its effects, is pressurization.
0.3  System components
A typical pressure differential system will comprise three basic components:
a) components for providing supply air and to extract air;
b) components for controlling the pressure difference between the space with higher pressure and the
adjoining space with lower pressure;
c) components for releasing air flowing through the door between the space with higher pressure to those
with lower pressure (to prevent unwanted pressure build up in this space).
Installations of pressure differential systems (PDS) may comprise:
— fans (temperature rated) if necessary;
— air or smoke control ducts to provide a passageway for the transmission of air or smoke;
— ventilation openings to provide leakage of air (including dampers, active or passive controlled);
— power supply;
— connecting cables;
— means of activation;
— means of pressure control;
— control panel;
— smoke control dampers in branches from the ductwork where the ductwork is situated outside the
protected enclosure;
— grilles and diffusers;
— door closers.
1)
The design of pressure differential systems is covered in ISO 21927-13 .
1)  To be published. Stage at the time of publication ISO/DIS 21927-13:2025.
PROOF/ÉPREUVE
vi
International Standard ISO 21927-6:2025(en)
Smoke and heat control systems —
Part 6:
Specification for pressure differential systems
1 Scope
This document applies to pressure differential system kits and components, positioned on the market and
intended to operate as part of a pressure differential system. The purpose of a pressure differential system
is to prevent protected spaces from smoke spread by using pressure difference and airflow. This document
specifies characteristics and test methods for components and kits for pressure differential systems to
produce and control the required pressure differential and airflow between protected and unprotected space.
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 13943, Fire safety — Vocabulary
ISO 21927-2, Smoke and heat control systems — Part 2: Specifications for natural smoke and heat exhaust
ventilators
ISO 21927-3, Smoke and heat control systems — Part 3: Specifications for powered smoke and heat exhaust
ventilators
ISO 21927-8, Smoke and heat control systems — Part 8: Smoke control dampers
EN 1363-1, Fire resistance tests — Part 1: General requirements
ISO 21927-7, Smoke and heat control systems — Part 7: Smoke ducts sections
ISO 21927-7, Smoke and heat control systems — Part 7: Smoke ducts sections
ISO 21927-8, Smoke and heat control systems — Part 8: Smoke control dampers
EN 13501-4, Fire classification of construction products and building elements — Part 4: Classification using
data from fire resistance tests on components of smoke control systems
3 Terms, definitions, symbols and abbreviated terms
3.1 Terms, definitions and abbreviated terms
For the purposes of this document, the terms and definitions given in ISO 13943 and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
PROOF/ÉPREUVE
3.1.1
air release
means by which pressurizing air or a mixture of pressurizing air and smoke is able to escape from the
accommodation or other unpressurized space to outside the building
3.1.2
control panel
multi-operational device to activate and/or control a PDS
3.1.3
depressurization
smoke control using pressure differentials between the protected space and the unprotected space with a
lower pressure in the unprotected space
3.1.4
pressure differential system
PDS
combination of at least one kit and additional components intended to produce pressure differential and
airflow between protected and unprotected spaces
3.1.5
pressurization
smoke control using pressure differentials between the protected space and the unprotected space with a
higher pressure in the protected space
3.1.6
pressure differential system
PDS
combination of at least two components which are necessary to produce and control the required pressure
differential and airflow-between protected and unprotected space
Note 1 to entry: The type of kit is dictated by the PDS design and objectives. Schematic overviews of different types
are given in Annex A.
3.1.7
active control
pressure control actuated from measured pressure and using external energy (e.g. motor driven damper,
frequency inverter-controlled fans, etc.)
3.1.8
barometric relief damper
damper activated by local pressure difference that opens to permit airflow and therefore controls the
pressure
3.1.9
activation signal
signal to initiate from stand-by to the active mode of the pressure differential system
3.2 Symbols
The symbols and abbreviations below are used in the document:
PROOF/ÉPREUVE
Symbol Unit Description
measured air release volume flow rate from space 1 (representing the protected space in
 3
m /h the building) to space 2 (representing the unprotected space in the building) via open air
V
ar
release path during the test (nominal value given by the manufacturer)
required leakage flow rate if necessary for the function of the PDS kit. If the building leakages
 3
V m /h (always present) are at the same rate or larger, during the test (nominal value given by the
RL
manufacturer), the component to produce the defined leakage is part of the PDS kit under test
m /h volume flow rate through temporary openings (e.g. open doors from staircases on differ-

V
ent levels from fire level, open escape/exit door) in case of pressurization during the test
TO
ps
(nominal value given by the manufacturer)
m /h volume flow rate through temporary openings (e.g. open doors from staircases on different

V
levels from fire level, open escape/exit door) in case of depressurization during the test
TO
dp
(nominal value given by the manufacturer)

m /h
V exhaust volume flow rate out of space 2 for combined systems
ex
 m /h
V required minimum leakage volume flow rate at nominal pressure difference Δp
Nom
rl
m /h lower limit of volume flow rate through air release

V
ar,ll

VV=⋅09,
ar,ll ar

m /h
V supply air volume flow rate measured at inlet nozzle
sa
m /h 
total controlled volume flow rate of the PDS kit as sum of flow rate air release V + flow
ar

V
TC

rate through temporary openings V (nominal value given by the manufacturer)
TC

m /h
V bypass air volume flow rate
BP
Pa
Δp pressure differential between space 1 and reference pressure (static pressure in test hall)
tr1
Pa
Δp pressure differential between space 2 and reference pressure (static pressure in test hall)
tr2
Pa nominal pressure differential to be maintained by the PDS kit with closed air release opening
Δp
nom
and closed temporary openings (static conditions)
Pa
Δp pressure difference across the open-air release path
ar
Pa
Δp Upper limit of nominal pressure differential ΔΔpP=⋅12,
Nom,ul Nom,ul Nom
s 
Δt Time period needed to establish volume flow rate V (flow criteria – see Figure 6)
V ar,ll
Δt s
Pressure stabilizing time period (pressure criteria – see 5.7)
p
s
Δt
time to establish volume flow rate in TCS cycle i
V ,i
s
Δt
pressure stabilizing time in TCS cycle i
p,i
−1
f s frequency of the frequency inverter from the PDS kit where equipped
−1
s minimal frequency of the frequency inverter at the passed test with all openings closed and
f
min
at lowest required leakage – shall be stated in the test report
−1
s highest frequency of the frequency inverter at the passed test with air release path and
f
max
temporary opening open and at highest required leakage – shall be stated in the test report
I A absorbed current of the fan (motor)
fan
TCS test cycle sequence
4 Characteristics
4.1 General
This clause gives details of the characteristics and additional test details. The structure of this clause is
mirrored in Clause 5. The characteristics are listed here, with the corresponding test reference in Clause 5.
NOTE 1 This structure was used as it mirrors the requirements for harmonized product standards to ensure all the
relevant subjects are covered.
PROOF/ÉPREUVE
For example, in 4.2.2.1 the characteristics for natural smoke and heat exhaust dampers are shown and the
matching 5.2.2.1 provides the test method. This is continued throughout these two clauses.
The kit shall be shown to be able to fulfil the specific pressure differential application that it is designed to
provide. To demonstrate this, certain components have their own requirements and will need to fulfil these.
Any component with no specific characteristics shown below shall be listed as part of the kit and included in
the kit testing.
— Where there is a need for air or smoke release (cold or hot) to the outside through an opening fitted with
a natural smoke and heat exhaust ventilator shall be used.
— Where air volume and pressure are to be controlled using mechanical pressure relief a barometric
damper or controlled damper in accordance with this document shall be used.
— Where ambient air is to be supplied using fans, the fans shall be further shown to be in accordance with
this document.
— Where air or smoke is to be extracted by the pressure differential systems (cold or hot) this shall be done
using powered heat exhaust ventilators (smoke control fans).
— Where air or smoke is to be extracted (cold or hot) using ductwork, the ductwork shall be smoke control
duct (Builders work shafts may be used as an option and this is not within the scope of this document).
— Where dampers are needed to open and close to provide a path for air or smoke (cold or hot) to the
outside and maintain compartmentation, these shall be smoke control dampers.
— Where volume control around high temperature fans is to be provided using motorized control dampers
these shall be hot gas control dampers in accordance with this document.
NOTE 2 Fans/shafts/ductwork used to balance stack effects in the staircase do not need to have a temperature rating.
4.2 Nominal activation conditions/sensitivity
4.2.1 Kit
The PDS kit shall be activated automatically by smoke detectors and it shall be possible to trigger it manually
by an external switch.
The following proxy characteristics shall be taken into account
a) the response time – see 4.3, and
b) the operational reliability – see 4.4.
In addition, the following components shall have their own characteristics when functioning as a part of the kit.
4.2.2 Components
4.2.2.1 Natural smoke and heat exhaust ventilators
The characteristics for nominal activation conditions/sensitivity in ISO 21927-2 shall be met – see 5.2.2.1.
4.2.2.2 Pressure control dampers (e.g. barometric dampers, motorized control dampers)
The following proxy characteristics shall be taken into account
a) the response time – see 4.3, and
b) the operational reliability – see 4.4.
PROOF/ÉPREUVE
4.2.2.3 Fans
4.2.2.3.1 Ambient air supply fans
The following proxy characteristics shall be taken into account
a) the response time – see 4.3, and
b) the operational reliability – see 4.4.
4.2.2.3.2 Smoke control fans (powered smoke and heat exhaust ventilators)
In addition to any response time required by the kit (4.3.1), the characteristics for nominal activation
conditions/sensitivity in ISO 21927-3 shall be met – see 5.2.2.3.2.
See also Annex C for additional tests with smoke fans controlled by frequency inverters.
4.2.2.4 Smoke control ducts
Smoke control ducts have no nominal activation conditions/sensitivity requirements as they have no
moving parts.
4.2.2.5 Smoke control dampers
The characteristics for nominal activation conditions/sensitivity in ISO 21927-8 shall be met – see 5.2.2.5.
4.2.2.6 Hot gas control dampers
The following proxy characteristics shall be taken into account
a) the response time – see 4.3,
b) the operational reliability – see 4.4, and
c) characteristics as determined in Annex B.
4.3 Response delay (response time)
4.3.1 Kit
4.3.1.1 General
The proxy characteristics in 4.3.1.2 and 4.3.1.3 shall be taken into account.
4.3.1.2 Initial response time
The kit shall achieve operating status within a time period of less than 60 s after the activation signal. This
shall be tested in accordance with 5.4.1.
4.3.1.3 Response time of door opening and door closing
The kit shall achieve at least 90 % of the nominal airflow rate within 3 s of a door being fully opened (opening
angle 90°) in accordance with test method in 5.4.1.2.
The kit shall reach the nominal pressure differential in the protected space Δp ±20 % within 3 s after a
nom
door to the unprotected space or a temporary opening is closed completely. The pressure differential shall
not exceed Δp = Δp ⋅ 1,2 for a time period of more than 3 s. This shall be demonstrated in accordance
nom,ul nom
with the test method in 5.4.1.
PROOF/ÉPREUVE
The kit shall re-establish behaviour under the conditions of the oscillating test in 5.4.1.11 even in the case of
several door closing/opening cycles in accordance with test method in 5.4.1.11.
4.3.2 Components
4.3.2.1 General
In addition, the following components shall have their own requirements when functioning as a part of the kit.
4.3.2.2 Natural smoke and heat exhaust ventilators
The characteristics for response delay (response time) in ISO 21927-2 shall be met – see 5.3.2.1.
4.3.2.3 Pressure control dampers (e.g. barometric dampers, motorized control dampers)
The pressure control dampers shall meet the response time characteristics as shown in 4.3.1 when tested as
part of the kit – see 5.3.2.2.
4.3.2.4 Fans
4.3.2.4.1 Ambient air supply fans
The ambient supply fans shall meet the response time characteristics as shown in 4.3.1 when tested as part
of the kit – see 5.3.2.3.1.
4.3.2.4.2 Smoke control fans (powered smoke and heat exhaust ventilators)
In addition to any response time required by the kit (4.3.1), if the product requires it, the characteristics for
nominal activation conditions/sensitivity in ISO 21927-3 shall be met – see 5.3.2.3.2.
4.3.2.5 Smoke control ducts
Smoke control ducts have no response delay requirements as they have no moving parts.
4.3.2.6 Smoke control dampers
The characteristics for response delay (response time) in ISO 21927-8 shall be met – see 5.3.2.5.
4.3.2.7 Hot gas control dampers
The characteristics shown in Annex B shall be reported against the listed classifications. The dampers shall
meet the requirements in 4.3.1 and move to the required position in less than 3 s (4.3.1) and it shall be
proven that the average operation time as determined in Annex B under elevated temperature conditions is
no more than plus 20 % of that determined at ambient temperature.
4.4 Operational reliability
4.4.1 Kit
The following proxy characteristics shall be taken into account: the ability of the kit to fulfil the volume flow
rate and pressurization values as part of the functionality test – see 5.4.1.
Complete the 10 000 cycles requirement.
In addition, the following components shall have their own requirements when functioning as a part of the kit.
PROOF/ÉPREUVE
4.4.2 Components
4.4.2.1 Natural smoke and heat exhaust ventilators
The characteristics for operational reliability in ISO 21927-2 shall be met – see 5.4.2.1.
4.4.2.2 Pressure control dampers (e.g. barometric dampers, motorized control dampers)
The pressure control dampers shall meet the operational reliability as shown in 4.4.1 when tested as part of
the kit – see 5.4.2.2.
4.4.2.3 Fans
4.4.2.3.1 Ambient air supply fans
The ambient supply fans shall meet the operational reliability characteristics as shown in 4.4.1 when tested
as part of the kit – see 5.4.2.3.1.
4.4.2.3.2 Smoke control fans (Powered smoke and heat exhaust ventilators)
In addition to any operational reliability required by the kit test (4.4.1), the smoke control fans shall meet
the operational reliability requirements of ISO 21927-3 – see 5.4.2.3.2.
See also Annex C for additional tests with smoke fans controlled by frequency inverters.
4.4.2.4 Smoke control ducts
Smoke control ducts have no operational reliability requirements as they have no moving parts.
4.4.2.5 Smoke control dampers
The characteristics for operational reliability in ISO 21927-8 shall be met – see 5.4.2.5.
4.4.2.6 Hot gas control dampers
The 10 operations at ambient and 10 operations at elevated temperature (see Annex B) shall be met before
being part of the kit test – see 4.4.1.
4.5 Effectiveness of smoke/hot gas extraction (air release/powered air release)
4.5.1 Kit
The following proxy characteristic shall be taken into account
— the ability of the kit to fulfil the operational reliability requirements – see 4.4.
4.5.2 Components
4.5.2.1 Natural smoke and heat exhaust ventilators
The aerodynamic free area and relevant loading reliability requirements of ISO 21927-2 shall be met – see
5.5.2.1.
4.5.2.2 Pressure control dampers (e.g. barometric dampers, motorized control dampers)
As a proxy characteristic the pressure control dampers shall meet the response time (4.3.1) and operational
reliability (4.4.1) when tested as part of the kit – see 5.5.2.2.
PROOF/ÉPREUVE
4.5.2.3 Fans
4.5.2.3.1 Ambient air supply fans
The ambient supply fans shall meet the operational reliability characteristics as shown in 4.4.1 when tested
as part of the kit – see 5.5.2.3.1.
4.5.2.3.2 Smoke control fans (Powered smoke and heat exhaust ventilators)
In addition to any operational reliability required by the kit test (see 4.4.1), the smoke control fans shall
meet the operational reliability req
...

ISO/PRF 21927-6:2025(en)
ISO/TC 21/SC 11
Secretariat: DIN
Date: 2025-09-29xx
Smoke and heat control systems —
Part 6:
Specification for pressure differential systems
Systèmes pour le contrôle des fumées et de la chaleur —
Partie 6: Spécifications relatives aux systèmes à différentiel de pression
PROOF
ISO/PRF 21927-6:2025(en)
© ISO 2025
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication
may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying,
or posting on the internet or an intranet, without prior written permission. Permission can be requested from either
ISO at the address below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: + 41 22 749 01 11
EmailE-mail: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
ISO/PRF 21927-6:2025(en)
Contents
Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions, symbols and abbreviated terms . 1
3.1 Terms, definitions and abbreviated terms . 1
3.2 Symbols . 2
4 Characteristics . 4
4.1 General . 4
4.2 Nominal activation conditions/sensitivity . 4
4.3 Response delay (response time) . 6
4.4 Operational reliability . 7
4.5 Effectiveness of smoke/hot gas extraction (air release/powered air release) . 8
4.6 Performance parameters under fire conditions . 9
4.7 Pressurization performance . 10
4.8 Fire resistance – Integrity (E) . 10
4.9 Fire resistance – Insulation (I) . 11
4.10 Fire resistance – Smoke leakage (S) . 12
4.11 Fire resistance – Mechanical stability . 13
4.12 Fire resistance – Maintenance of cross section . 14
4.13 Durability . 15
5 Test methods . 16
5.1 General . 16
5.2 Nominal activation conditions/sensitivity . 17
5.3 Response delay (response time) . 17
5.4 Operational reliability . 18
5.5 Effectiveness of smoke/hot gas extraction . 28
5.6 Performance parameters under fire conditions . 29
5.7 Pressurization performance . 30
5.8 Fire resistance – Integrity (E) . 31
5.9 Fire resistance – Insulation (I) . 31
5.10 Fire resistance – Smoke leakage (S) . 32
5.11 Fire resistance – Mechanical stability . 33
5.12 Fire resistance – Maintenance of cross section . 34
5.13 Durability . 34
6 Verification of performance . 35
6.1 Type testing . 35
6.2 Factory production control (FPC) . 37
7 Marking, labelling and packaging . 40
Annex A (normative) Pressure differential kit types (pressurization) . 41
Annex B (normative) Test method for hot gas control damper at elevated temperature . 53
Annex C (normative) Test required for powered smoke and heat exhaust ventilators with
frequency inverter and operated with variable speed at elevated temperature . 57
Annex D (normative) Installation and maintenance document . 59
Bibliography . 60

iii
ISO/PRF 21927-6:2025(en)
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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights
in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s)
which may be required to implement this document. However, implementers are cautioned that this may not
represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
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 the European Committee for Standardization (CEN) (as EN 12101-6:2022)
and was adopted, without modification other than those given below by Technical Committee ISO/TC 21,
Equipment for fire protection and fire fighting, Subcommittee SC 11, Smoke and heat control systems and
components.”.
— — Editorial changes in 3.2clause 3.2,, Symbols: the subscript elements are not written in italics.
— — Normative references: the normative references were changed from the European Standard of the
serieseries EN 12101-xx into the ISO standard of the serieseries ISO 21927-xx.
— Clause 7— Clause 7:: Headline "Table 3table 3" was added, rephrase of and the sentence above the table
was rephrased.
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/PRF 21927-6:2025(en)
Introduction
0.1 0.1  Objectives of pressure differential systems
Pressure differential systems offer the facility of maintaining tenable conditions in protected spaces, for
example: escape routes, firefighting access routes, firefighting lift shafts, lobbies, staircases, and other spaces
that require being kept free of smoke. It is necessary to determine not only where the fresh air supply for
pressurization is to be introduced into a building, but also where that air and smoke will leave the building
and what paths it will follow in the process.
The aim therefore is to establish a pressure gradient from the protected space to the unprotected space (fire
room) while the doors are closed, and an airflow while the doors are open.
0.2 0.2  Smoke control methods
The effect of the air movement forces, described above, are to create pressure differentials across the
partitions, walls and floors and can cause smoke to spread to spaces remote from the fire source. The
technique most commonly used to limit the degree of smoke spread, or to control its effects, is pressurization.
0.3 0.3  System components
A typical pressure differential system will comprise three basic components:
a) a) components for providing supply air and to extract air;
b) b) components for controlling the pressure difference between the space with higher pressure
and the adjoining space with lower pressure;
c) c) components for releasing air flowing through the door between the space with higher pressure
to those with lower pressure (to prevent unwanted pressure build up in this space).
Installations of pressure differential systems (PDS) may comprise:
— — fans (temperature rated) if necessary;
— — air or smoke control ducts to provide a passageway for the transmission of air or smoke;
— — ventilation openings to provide leakage of air (including dampers, active or passive controlled);
— — power supply;
— — connecting cables;
— — means of activation;
— — means of pressure control;
— — control panel;
— — smoke control dampers in branches from the ductwork where the ductwork is situated outside the
protected enclosure;
— — grilles and diffusers;
— — door closers.
v
ISO/PRF 21927-6:2025(en)
1)
The design of pressure differential systems is covered in ISO/DIS 21927-13. .

1)
To be published. Stage at the time of publication ISO/DIS 21927-13:2025.
vi
ISO/PRF 21927-6:2025(en)
Smoke and heat control systems —
Part 6:
Specification for pressure differential systems
1 Scope
This document applies to pressure differential system kits and components, positioned on the market and
intended to operate as part of a pressure differential system. The purpose of a pressure differential system is
to prevent protected spaces from smoke spread by using pressure difference and airflow. This document
specifies characteristics and test methods for components and kits for pressure differential systems to
produce and control the required pressure differential and airflow between protected and unprotected space.
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 13943, Fire safety — Vocabulary
ISO 21927--2, Smoke and heat control systems — Part 2: Specifications for natural smoke and heat exhaust
ventilators
ISO 21927--3, Smoke and heat control systems — Part 3: Specifications for powered smoke and heat exhaust
ventilators
ISO 21927--8, Smoke and heat control systems — Part 8: Smoke control dampers
EN 1363--1, Fire resistance tests — Part 1: General requirements
ISO 21927--7, Smoke and heat control systems — Part 7: Smoke ducts sections
ISO 21927--7, Smoke and heat control systems — Part 7: Smoke ducts sections
ISO 21927--8, Smoke and heat control systems — Part 8: Smoke control dampers
EN 13501--4, Fire classification of construction products and building elements — Part 4: Classification using
data from fire resistance tests on components of smoke control systems
3 Terms, definitions, symbols and abbreviated terms
3.1 Terms, definitions and abbreviated terms
For the purposes of this document, the terms and definitions given in ISO 13943 and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— — ISO Online browsing platform: available at https://www.iso.org/obp
— — IEC Electropedia: available at https://www.electropedia.org/
ISO/PRF 21927-6:2025(en)
3.1.1 3.1.1
air release
means by which pressurizing air or a mixture of pressurizing air and smoke is able to escape from the
accommodation or other unpressurized space to outside the building
3.1.2 3.1.2
control panel
multi-operational device to activate and/or control a PDS
3.1.3 3.1.3
depressurization
smoke control using pressure differentials between the protected space and the unprotected space with a
lower pressure in the unprotected space
3.1.4 3.1.4
pressure differential system
PDS
combination of at least one kit and additional components intended to produce pressure differential and
airflow between protected and unprotected spaces
3.1.5 3.1.5
pressurization
smoke control using pressure differentials between the protected space and the unprotected space with a
higher pressure in the protected space
3.1.6 3.1.6
pressure differential system
PDS
combination of at least two components which are necessary to produce and control the required pressure
differential and airflow-between protected and unprotected space
Note 1 to entry: The type of kit is dictated by the PDS design and objectives. Schematic overviews of different types are
given in Annex AAnnex A.
3.1.7 3.1.7
active control
pressure control actuated from measured pressure and using external energy (e.g. motor driven damper,
frequency inverter-controlled fans, etc.)
3.1.8 3.1.8
barometric relief damper
damper activated by local pressure difference that opens to permit airflow and therefore controls the pressure
3.1.9 3.1.9
activation signal
signal to initiate from stand-by to the active mode of the pressure differential system
3.2 Symbols
The symbols and abbreviations below are used in the document:
Symbol Unit Description
measured air release volume flow rate from space 1 (representing the protected space in
˙
𝑉𝑉 m /h the building) to space 2 (representing the unprotected space in the building) via open air
ar
release path during the test (nominal value given by the manufacturer)
ISO/PRF 21927-6:2025(en)
Symbol Unit Description
required leakage flow rate if necessary for the function of the PDS kit. If the building
leakages (always present) are at the same rate or larger, during the test (nominal value
˙ 3
𝑉𝑉 m /h
RL
given by the manufacturer), the component to produce the defined leakage is part of the
PDS kit under test
m /h volume flow rate through temporary openings (e.g. open doors from staircases on
˙
𝑉𝑉
different levels from fire level, open escape/exit door) in case of pressurization during
TO
ps
the test (nominal value given by the manufacturer)
m /h volume flow rate through temporary openings (e.g. open doors from staircases on
˙
𝑉𝑉
different levels from fire level, open escape/exit door) in case of depressurization during
TO
dp
the test (nominal value given by the manufacturer)
˙
m /h exhaust volume flow rate out of space 2 for combined systems
𝑉𝑉
ex
˙
𝑉𝑉 m /h required minimum leakage volume flow rate at nominal pressure difference 𝛥𝛥𝑝𝑝
rl Nom
m /h lower limit of volume flow rate through air release
˙
𝑉𝑉
ar,ll
˙ ˙
𝑉𝑉 = 0,9⋅  𝑉𝑉
𝑎𝑎𝑎𝑎,𝑙𝑙𝑙𝑙 𝑎𝑎𝑎𝑎
˙
𝑉𝑉 m /h supply air volume flow rate measured at inlet nozzle
sa
˙
m /h
total controlled volume flow rate of the PDS kit as sum of flow rate air release 𝑉𝑉 + flow
𝑎𝑎𝑎𝑎
˙
𝑉𝑉
TC
˙
rate through temporary openings 𝑉𝑉 (nominal value given by the manufacturer)
TC
˙
m /h bypass air volume flow rate
𝑉𝑉
BP
Pa pressure differential between space 1 and reference pressure (static pressure in test
𝛥𝛥𝑝𝑝
tr1
hall)
Pa pressure differential between space 2 and reference pressure (static pressure in test
𝛥𝛥𝑝𝑝
tr2
hall)
Pa nominal pressure differential to be maintained by the PDS kit with closed air release
𝛥𝛥𝑝𝑝
nom
opening and closed temporary openings (static conditions)
𝛥𝛥𝑝𝑝 Pa pressure difference across the open-air release path
ar
𝛥𝛥𝑝𝑝 Pa Upper limit of nominal pressure differential 𝛥𝛥𝑝𝑝 = 1,2⋅𝛥𝛥𝑃𝑃
Nom,ul Nom,ul Nom
˙
s Time period needed to establish volume flow rate 𝑉𝑉 (flow criteria – see
ar,ll
𝛥𝛥𝑡𝑡
V
Figure 6Figure 6))
𝛥𝛥𝑡𝑡 s
Pressure stabilizing time period (pressure criteria – see 5.75.7))
p
𝛥𝛥𝑡𝑡 s time to establish volume flow rate in TCS cycle i
𝑉𝑉 ,i
𝛥𝛥𝑡𝑡 s pressure stabilizing time in TCS cycle i
p,i
−1
frf s frequency of the frequency inverter from the PDS kit where equipped
−1
s minimal frequency of the frequency inverter at the passed test with all openings closed
fr f
min min
and at lowest required leakage – shall be stated in the test report
−1
s highest frequency of the frequency inverter at the passed test with air release path and
frmaxfmax temporary opening open and at highest required leakage – shall be stated in the test
report
Ifan A absorbed current of the fan (motor)
TCS  test cycle sequence
ISO/PRF 21927-6:2025(en)
4 Characteristics
4.1 General
This clause gives details of the characteristics and additional test details. The structure of this clause is
mirrored in Clause 5Clause 5. The characteristics are listed here, with the corresponding test reference in
Clause 5Clause 5.
NOTE 1 This structure was used as it mirrors the requirements for harmonized product standards to ensure all the
relevant subjects are covered.
For example, in 4.2.2.1Clause 4.2.2.1 the characteristics for natural smoke and heat exhaust dampers are
shown and the matching 5.2.2.1Clause 5.2.2.1 provides the test method. This is continued throughout these
2two clauses.
The kit shall be shown to be able to fulfil the specific pressure differential application that it is designed to
provide. To demonstrate this, certain components have their own requirements and will need to fulfil these.
Any component with no specific characteristics shown below shall be listed as part of the kit and included in
the kit testing.
— — Where there is a need for air or smoke release (cold or hot) to the outside through an opening fitted
with a natural smoke and heat exhaust ventilator shall be used.
— — Where air volume and pressure are to be controlled using mechanical pressure relief a barometric
damper or controlled damper in accordance with this document shall be used.
— — Where ambient air is to be supplied using fans, the fans shall be further shown to be in accordance
with this document.
— — Where air or smoke is to be extracted by the pressure differential systems (cold or hot) this shall be
done using powered heat exhaust ventilators (smoke control fans).
Where air or smoke is to be extracted (cold or hot) using ductwork, the ductwork shall be smoke
— —
control duct (Builders work shafts may be used as an option and this is not within the scope of this
document).
— — Where dampers are needed to open and close to provide a path for air or smoke (cold or hot) to the
outside and maintain compartmentation, these shall be smoke control dampers.
— — Where volume control around high temperature fans is to be provided using motorized control
dampers these shall be hot gas control dampers in accordance with this document.
NOTE 2 Fans/shafts/ductwork used to balance stack effects in the staircase do not need to have a temperature rating.
4.2 Nominal activation conditions/sensitivity
4.2.1 Kit
The PDS kit shall be activated automatically by smoke detectors and it shall be possible to trigger it manually
by an external switch.
The following proxy characteristics shall be taken into account:
a) a) the response time – see 4.34.3;, and
b) b) the operational reliability – see 4.44.4.
ISO/PRF 21927-6:2025(en)
In addition, the following components shall have their own characteristics when functioning as a part of the
kit.
4.2.2 Components
4.2.2.1 Natural smoke and heat exhaust ventilators
The characteristics for nominal activation conditions/sensitivity in ISO 21927-2 shall be met –
see 5.2.2.15.2.2.1.
4.2.2.2 Pressure control dampers (e.g. barometric dampers, motorized control dampers)
The following proxy characteristics shall be taken into account:
a) a) the response time – see 4.34.3;, and
b) b) the operational reliability – see 4.44.4.
4.2.2.3 Fans
4.2.2.3.1 Ambient air supply fans
The following proxy characteristics shall be taken into account:
a) a) the response time – see 4.34.3;, and
b) b) the operational reliability – see 4.44.4.
4.2.2.3.2 Smoke control fans (powered smoke and heat exhaust ventilators)
In addition to any response time required by the kit (4.3.1(4.3.1),), the characteristics for nominal activation
conditions/sensitivity in ISO 21927-3 shall be met – see 5.2.2.3.25.2.2.3.2.
See also Annex CAnnex C for additional tests with smoke fans controlled by frequency inverters.
4.2.2.4 Smoke control ducts
Smoke control ducts have no nominal activation conditions/sensitivity requirements as they have no moving
parts.
4.2.2.5 Smoke control dampers
The characteristics for nominal activation conditions/sensitivity in ISO 21927-8 shall be met – see
5.2.2.55.2.2.5.
4.2.2.6 Hot gas control dampers
The following proxy characteristics shall be taken into account:
a) a) the response time – see 4.34.3; and,
b) b) the operational reliability – see 4.44.4;, and
c) c) characteristics as determined in Annex BAnnex B.
ISO/PRF 21927-6:2025(en)
4.3 Response delay (response time)
4.3.1 Kit
4.3.1.1 General
The proxy characteristics in 4.3.1.24.3.1.2 and 4.3.1.34.3.1.3 shall be taken into account.
4.3.1.2 Initial response time
The kit shall achieve operating status within a time period of less than 60 s after the activation signal. This
shall be tested in accordance with 5.4.15.4.1.
4.3.1.3 Response time of door opening and door closing
The kit shall achieve at least 90 % of the nominal airflow rate within 3 s of a door being fully opened (opening
angle 90°) in accordance with test method in 5.4.1.25.4.1.2.
The kit shall reach the nominal pressure differential in the protected space Δp ±20 % within 3 s after a door
nom
to the unprotected space or a temporary opening is closed completely. The pressure differential shall not
exceed Δp = Δp ⋅ 1,2 for a time period of more than 3 s. This shall be demonstrated in accordance with
nom,ul nom
the test method in 5.4.15.4.1.
The kit shall re-establish behaviour under the conditions of the oscillating test in 5.4.1.115.4.1.11 even in the
case of several door closing/opening cycles in accordance with test method in 5.4.1.115.4.1.11.
4.3.2 Components
4.3.2.1 General
In addition, the following components shall have their own requirements when functioning as a part of the kit.
4.3.2.2 Natural smoke and heat exhaust ventilators
The characteristics for response delay (response time) in ISO 21927-2 shall be met – see 5.3.2.15.3.2.1.
4.3.2.3 Pressure control dampers (e.g. barometric dampers, motorized control dampers)
The pressure control dampers shall meet the response time characteristics as shown in 4.3.14.3.1 when tested
as part of the kit – see 5.3.2.25.3.2.2.
4.3.2.4 Fans
4.3.2.4.1 Ambient air supply fans
4.3.2.41.1.1.1 Fans
4.3.2.4.11.1.1.1.1 Ambient air supply fans
The ambient supply fans shall meet the response time characteristics as shown in 4.3.14.3.1 when tested as
part of the kit – see 5.3.2.3.15.3.2.3.1.
4.3.2.4.2 Smoke control fans (powered smoke and heat exhaust ventilators)
In addition to any response time required by the kit (4.3.1(4.3.1),), if the product requires it, the characteristics
for nominal activation conditions/sensitivity in ISO 21927-3 shall be met – see 5.3.2.3.25.3.2.3.2.
ISO/PRF 21927-6:2025(en)
4.3.2.5 Smoke control ducts
Smoke control ducts have no response delay requirements as they have no moving parts.
4.3.2.6 Smoke control dampers
The characteristics for response delay (response time) in ISO 21927-8 shall be met – see 5.3.2.55.3.2.5.
4.3.2.7 Hot gas control dampers
The characteristics shown in Annex BAnnex B shall be reported against the listed classifications. The dampers
shall meet the requirements in 4.3.14.3.1 and move to the required position in less than 3 s (4.3.1(4.3.1)) and
it shall be proven that the average operation time as determined in Annex BAnnex B under elevated
temperature conditions is no more than plus 20 % of that determined at ambient temperature.
4.4 Operational reliability
4.4.1 Kit
The following proxy characteristics shall be taken into account: the ability of the kit to fulfil the volume flow
rate and pressurization values as part of the functionality test – see 5.4.15.4.1.
Complete the 10 000 cycles requirement.
In addition, the following components shall have their own requirements when functioning as a part of the kit.
4.4.2 Components
4.4.2.1 Natural smoke and heat exhaust ventilators
The characteristics for operational reliability in ISO 21927-2 shall be met – see 5.4.2.15.4.2.1.
4.4.2.2 Pressure control dampers (e.g. barometric dampers, motorized control dampers)
The pressure control dampers shall meet the operational reliability as shown in 4.4.14.4.1 when tested as part
of the kit – see 5.4.2.25.4.2.2.
4.4.2.3 Fans
4.4.2.3.1 Ambient air supply fans
4.4.2.31.1.1.1 Fans
4.4.2.3.11.1.1.1.1 Ambient air supply fans
The ambient supply fans shall meet the operational reliability characteristics as shown in 4.4.14.4.1 when
tested as part of the kit – see 5.4.2.3.15.4.2.3.1.
4.4.2.3.2 Smoke control fans (Powered smoke and heat exhaust ventilators)
In addition to any operational reliability required by the kit test (4.4.1(4.4.1),), the smoke control fans shall
meet the operational reliability requirements of ISO 21927-3 – see 5.4.2.3.25.4.2.3.2.
See also Annex CAnnex C for additional tests with smoke fans controlled by frequency inverters.
ISO/PRF 21927-6:2025(en)
4.4.2.4 Smoke control ducts
Smoke control ducts have no operational reliability requirements as they have no moving parts.
4.4.2.5 Smoke control dampers
The characteristics for operational reliability in ISO 21927-8 shall be met – see 5.4.2.55.4.2.5.
4.4.2.6 Hot gas control dampers
The 10 operations at ambient and 10 operations at elevated temperature (see Annex BAnnex B)) shall be met
before being part of the kit test – see 4.4.14.4.1.
4.5 Effectiveness of smoke/hot gas extraction (air release/powered air release)
4.5.1 Kit
The following proxy characteristic shall be taken into account:
— — the ability of the kit to fulfil the operational reliability requirements – see 4.44.4.
4.5.2 Components
4.5.2.1 Natural smoke and heat exhaust ventilators
The aerodynamic free area and relevant loading reliability requirements of ISO 21927-2 shall be met – see
5.5.2.15.5.2.1.
4.5.2.2 Pressure control dampers (e.g. barometric dampers, motorized control dampers)
As a proxy characteristic the pressure control dampers shall meet the response time (4.3.1(4.3.1)) and
operational reliability (4.4.1(4.4.1)) when tested as part of the kit – see 5.5.2.25.5.2.2.
4.5.2.31.1.1.1 Fans
4.5.2.3.11.1.1.1.1 Ambient air supply fans
4.5.2.3 Fans
4.5.2.3.1 Ambient air supply fans
The ambient supply fans shall meet the operational reliability characteristics as shown in 4.4.14.4.1 when
tested as part of the kit – see 5.5.2.3.15.5.2.3.1.
4.5.2.3.2 Smoke control fans (Powered smoke and heat exhaust ventilators)
In addition to any operational reliability required by the kit test (see 4.4.14.4.1),), the smoke control fans shall
meet the operational reliability requirements of ISO 21927-3 – see 5.5.2.3.25.5.2.3.2.
See also Annex CAnnex C for additional tests with smoke fans controlled by frequency inverters.
4.5.2.4 Smoke control ducts
The maintenance of cross-sectional area and no collapse requirements of the duct fire resistance tests
EN 1366--8 (multi-compartment) or EN 1366--9 (single compartment) shall be met (not necessarily the
section requirements) – see 5.5.2.45.5.2.4.
ISO/PRF 21927-6:2025(en)
4.5.2.5 Smoke control dampers
The maintenance of cross-sectional area requirements of ISO 21927-8 shall be met – see 5.5.2.45.5.2.4.
4.5.2.6 Hot gas control dampers
As a proxy characteristic, the hot gas control dampers shall meet the response time (see 4.3.14.3.1)) and
operational reliability (4.4.1(4.4.1)) when tested as part of the kit – see 5.5.2.65.5.2.6.
4.6 Performance parameters under fire conditions
4.6.1 Kit
The following proxy characteristic shall be taken into account:
— — the ability of the kit to fulfil the operational reliability requirements – see 4.44.4.
4.6.2 Components
4.6.2.1 Natural smoke and heat exhaust ventilators
The aerodynamic free area and relevant loading reliability requirements of ISO 21927-2 shall be met – see
5.6.2.15.6.2.1.
4.6.2.2 Pressure control dampers (e.g. barometric dampers, motorized control dampers)
As a proxy characteristic the pressure control dampers shall meet the response time (4.3.1(4.3.1)) and
operational reliability (4.4.1(4.4.1)) when tested as part of the kit – see 5.6.2.25.6.2.2.
4.6.2.3 Fans
4.6.2.3.1 Ambient air supply fans
4.6.2.31.1.1.1 Fans
4.6.2.3.11.1.1.1.1 Ambient air supply fans
The ambient supply fans shall meet the operational reliability characteristics as shown in 4.4.14.4.1 when
tested as part of the kit – see 5.6.2.3.15.6.2.3.1.
4.6.2.3.2 Smoke control fans (powered smoke and heat exhaust ventilators)
In addition to any operational reliability required by the kit test (4.4.1(4.4.1),), the smoke control fans shall
meet the operational reliability requirements of ISO 21927-3 – see 5.6.2.3.25.6.2.3.2.
See also Annex CAnnex C for additional tests with smoke fans controlled by frequency inverters.
4.6.2.4 Smoke control ducts
The maintenance of cross-sectional area and no collapse requirements of the duct fire resistance tests
EN 1366--8 (multi-compartment) or EN 1366--9 (single compartment) shall be met (not necessarily the
section requirements) – see 5.5.2.45.5.2.4.
4.6.2.5 Smoke control dampers
The maintenance of cross-sectional area requirements of ISO 21927-8 shall be met – see 5.6.2.55.6.2.5.
ISO/PRF 21927-6:2025(en)
4.6.2.6 Hot gas control dampers
As a proxy characteristic, the hot gas control dampers shall meet the response time (see 4.3.14.3.1)) and
operational reliability (see 4.4.14.4.1)) when tested as part of the kit – see 5.6.2.65.6.2.6.
4.7 Pressurization performance
4.7.1 Kit
The following proxy characteristic shall be taken into account:
— — the ability of the kit to fulfil the operational reliability requirements – see 4.44.4.
4.7.2 Components
4.7.2.1 Natural smoke and heat exhaust ventilators
The natural smoke and heat exhaust ventilators shall open in less than 60 s to meet the requirements of
ISO 21927-2 – see 5.7.2.15.7.2.1.
4.7.2.2 Pressure control dampers (e.g. barometric dampers, motorized control dampers)
As a proxy characteristic the pressure control dampers shall meet the response time (see 4.3.14.3.1)) and
operational reliability (4.4.1(4.4.1)) when tested as part of the kit – see 5.7.2.25.7.2.2.
4.7.2.31.1.1.1 Fans
4.7.2.3.11.1.1.1.1 Ambient air supply fans
4.7.2.3 Fans
4.7.2.3.1 Ambient air supply fans
As a proxy characteristic, if the fan is controlled to change the pressure, it shall meet the response time (see
4.3.14.3.1)) and operational reliability (see 4.4.14.4.1)) when tested as part of the kit – see 5.7.2.3.15.7.2.3.1.
4.7.2.4 Smoke control ducts
The relevant leakage requirements of the duct fire resistance tests EN 1366--8 (multi-compartment) or
EN 1366--9 (single compartment) shall be met (not necessarily the section requirements) – see 5.7.2.45.7.2.4.
4.7.2.5 Smoke control dampers
The S classification leakage requirements of ISO 21927-8 shall be met – see 5.7.25.7.2.
4.7.2.6 Hot gas control dampers
As a proxy characteristic, the hot gas control dampers shall meet the response time (see 4.3.14.3.1)) and
operational reliability (4.4.1(4.4.1)) when tested as part of the kit – see 5.7.2.65.7.2.6.
4.8 Fire resistance – Integrity (E)
4.8.1 Kit
The kit has no inherent fire resistance integrity, but the following proxy characteristics for specific
components shall be taken into account where this is described in the relevant standard.
ISO/PRF 21927-6:2025(en)
4.8.2 Components
4.8.2.1 Natural smoke and heat exhaust ventilators
No fire resistance requirements – ISO 21927-2 tests only the ability to open.
4.8.2.2 Pressure control dampers (e.g. barometric dampers, motorized control dampers)
No fire resistance requirements.
4.8.2.3 Fans
4.8.2.3.1 Ambient air supply fans
No fire resistance requirements.
4.8.2.3.2 Smoke control fans (powered smoke and heat exhaust ventilators)
No fire resistance requirements – elevated temperature only – shall demonstrate the characteristics required
by ISO 21927-3.
4.8.2.4 Smoke control ducts
Single compartment smoke control ducts shall have an E classification in accordance with EN 13501--4
having been tested in accordance with the duct elevated temperature test EN 1366--9 (single compartment)
and not necessarily the section requirements – see 5.8.2.45.8.2.4.
Multi compartment smoke control ducts shall have an E classification in accordance with EN 13501--4 having
been tested in accordance with the duct fire resistance test EN 1366--8 (multi-compartment) and not
necessarily the section requirements – see 5.8.2.45.8.2.4.
4.8.2.5 Smoke control dampers
Single compartment smoke control dampers shall have an E classification in accordance with EN 13501--4
and meet the requirements of ISO 21927-8 – see 5.8.2.55.8.2.5.
Multi compartment smoke control dampers shall have an E classification in accordance with EN 13501--4 and
meet the requirements of ISO 21927-8 – see 5.8.2.55.8.2.5.
4.8.2.6 Hot gas control dampers
No fire resistance requirements – elevated temperature only.
4.9 Fire resistance – Insulation (I)
4.9.1 Kit
The kit has no inherent fire resistance insulation but the following proxy characteristics for specific
components shall be taken into account where this is described in the relevant standard.
4.9.2 Components
4.9.2.1 Natural smoke and heat exhaust ventilators
No fire resistance insulation requirements.
ISO/PRF 21927-6:2025(en)
4.9.2.2 Pressure control dampers (e.g. barometric dampers, motorized control dampers)
No fire resistance insulation requirements.
4.9.2.3 Fans
4.9.2.3.1 Ambient air supply fans
No fire resistance insulation requirements.
4.9.2.3.2 Smoke control fans (powered smoke and heat exhaust ventilators)
No fire resistance insulation requirements.
4.9.2.4 Smoke control ducts
Single compartment smoke control ducts: No fire resistance insulation requirements.
Multi compartment smoke control ducts shall have an EI classification in accordance with EN 13501--4 and
the duct fire resistance test EN 1366--8 (multi-compartment) and not necessarily the section requirements –
see 5.9.2.45.9.2.4.
4.9.2.5 Smoke control dampers
Single compartment smoke control dampers: no fire resistance insulation requirements.
Multi compartment smoke control dampers shall have an EI classification in accordance with EN 13501--4
and meet the requirements of ISO 21927-8 – see 5.9.2.55.9.2.5.
4.9.2.6 Hot gas control dampers
No fire resistance requirements – elevated temperature only.
4.10 Fire resistance – Smoke leakage (S)
4.10.1 Kit
The kit has no inherent fire resistance leakage, but the following proxy characteristics for specific components
shall be taken into account where this is described in the relevant standard.
4.10.2 Components
4.10.2.1 Natural smoke and heat exhaust ventilators
No fire resistance leakage requirements.
4.10.2.2 Pressure control dampers (e.g. barometric dampers, motorized control dampers)
No fire resistance leakage requirements.
4.10.2.3 Fans
4.10.2.3.1 Ambient air supply fans
No fire resistance leakage requirements.
ISO/PRF 21927-6:2025(en)
4.10.2.3.2 Smoke control fans (powered smoke and heat exhaust ventilators)
No fire resistance leakage requirements.
4.10.2.4 Smoke control ducts
Single compartment smoke control ducts shall have an E S classification in accordance with EN 13501--4
and the duct elevated temperature test EN 1366--9 (single compartment) and not necessarily the section
requirements – see 5.10.2.45.10.2.4.
Multi compartment smoke control ducts shall have an EI S classification in accordance with EN 13501--4 and
the duct fire resistance test EN 1366--8 (multi-compartment) and not necessarily the section requirements –
see 5.10.2.45.10.2.4.
4.10.2.5 Smoke control dampers
Single compartment smoke control dampers shall have an E S classification in accordance with EN 13501--
4 and meet the requirements of ISO 21927-8 – see 5.10.2.55.10.2.5.
Multi-compartment smoke control dampers shall have an E S or EI S classification in accordance with
EN 13501--4 and meet the requirements of ISO 21927-8 – see 5.10.2.55.10.2.5.
4.10.2.6 Hot gas control dampers
No fire resistance leakage requirements.
NOTE Ambient leakage test information is available from the leakage test required in Annex BAnnex B.
4.11 Fire resistance – Mechanical stability
4.11.1 Kit
The kit has no inherent fire resistance mechanical stability, but the following proxy characteristics for specific
components shall be taken into account where this is required by the relevant standard.
4.11.2 Components
4.11.2.1 Natural smoke and heat exhaust ventilators
No fire resistance mechanical stability requirements – elevated temperature ISO 21927-2 tests only.
4.11.2.2 Pressure control dampers (e.g. barometric dampers, motorized control dampers)
No fire resistance requirements.
4.11.2.3 Fans
4.11.2.3.1 Ambient air supply fans
No fire resistance requirements for mechanical stability.
4.11.2.3.2 Smoke control fans (powered smoke and heat exhaust ventilators)
No fire resistance requirements for mechanical stability – elevated temperature only – ISO 21927-3.
ISO/PRF 21927-6:2025(en)
4.11.2.4 Smoke control ducts
Single compartment smoke control ducts shall have an E classification in accordance with EN 13501--4 and
the duct elevated temperature test EN 1366--9 (single compartment) and not necessarily the section
requirements – see 5.11.2.45.11.2.4.
Multi compartment smoke control ducts shall have an E classification in accordance with EN 13501--4 and the
duct fire resistance test EN 1366--8 (multi-compartment) and not necessarily the section requirements – see
5.11.2.45.11.2.4.
4.11.2.5 Smoke control dampers
Single compartment smoke control dampers shall have an E classification in accordance with EN 13501--4
and meet the requirements of ISO 21927-8 – see 5.11.2.55.11.2.5.
Multi compartment smoke control dampers shall have an E classification in accordance with EN 13501--4 and
meet the requirements of ISO 21927-8 – see 5.11.2.55.11.2.5.
4.11.2.6 Hot gas control dampers
No fire resistance requirements for mechanical stability – elevated temperature only.
4.12 Fire resistance – Maintenance of cross section
4.12.1 Kit
The kit has no inherent fire resistance maintenance of cross section, but the following proxy characteristics
for specific components shall be taken into account where this is required by the relevant standard.
4.12.2 Components
4.12.2.1 Natural smoke and heat exhaust ventilators
No fire resistance requirements for the maintenance of cross sections – elevated temperature ISO 21927-2
tests only.
4.12.2.2 Pressure control dampers (e.g. barometric dampers, motorized control dampers)
No fire resistance requirements for the maintenance of
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