prEN ISO 13349

Fans - Vocabulary and definitions of categories (ISO/DIS 13349:2021)

Ventilatoren - Terminologie und Klassifizierung (ISO/DIS 13349:2021)

Diese Internationale Norm definiert Begriffe und Klassen von Ventilatoren für alle Anwendungen.
Sie ist nicht anwendbar in Bezug auf die elektrische Sicherheit.

Ventilateurs - Vocabulaire et définitions des catégories (ISO/DIS 13349:2021)

Ventilatorji - Slovar in definicije kategorij (ISO/DIS 13349:2021)

General Information

• Status: Not Published
• Publication Date: 08-Feb-2023
• ICS: 01.040.23 - Fluid systems and components for general use (Vocabularies)
• ICS: 23.120 - Ventilators. Fans. Air-conditioners
• Technical Committee: CEN/TC 156 - Ventilation for buildings
• Drafting Committee: CEN/TC 156/WG 17 - Fans
• Current Stage: 4097 - End of interruption of work - split/merged
• Start Date: 19-Jan-2022
• Completion Date: 14-Apr-2025
• Ref Project: oSIST prEN ISO 13349:2021 - Fans - Vocabulary and definitions of categories (ISO/DIS 13349:2021)

Relations

• Revises: EN ISO 13349:2010 - Fans - Vocabulary and definitions of categories (ISO 13349:2010)
• Effective Date: 11-May-2020

Overview

prEN ISO 13349 (ISO/DIS 13349:2021) is a draft International Standard prepared by ISO/TC 117 that specifies vocabulary and category definitions for fans. It standardizes terms, symbols and units used across the air-moving industry to reduce ambiguity in specification, testing and procurement. The second edition cancels and replaces the first edition (ISO 13349:2010) and aligns terminology with industry documents from Eurovent, AMCA, VDMA, AFNOR and UNI where applicable.

Key Topics

• Scope and purpose: Defines terms and definitions for fans used for all purposes (not covering electrical safety specifics).
• Core definition: A fan is a rotary-bladed machine that transfers mechanical energy to maintain continuous gas flow; typically its work per unit mass does not exceed 25 kJ/kg (above that threshold the machine is a turbocompressor).
• Terms and definitions: Includes definitions such as driven fan, non-driven (bare shaft) fan, integrated (embedded) fan, stand-alone fan, air and standard air.
• Symbols and units: Lists symbols, multiples of primary units, units of time and temperature conventions relevant to fan reporting and testing.
• Fan categories: Comprehensive categorization by:
  • installation arrangement (categories A–E: combinations of free/ducted inlet and outlet, with/without partition),
  • suitability for fan pressure (work per unit mass, pressure considerations),
  • construction suitability (casing types, gas-tight or hot-gas fans, smoke-ventilating designation),
  • transmission arrangements and inlet/outlet conditions,
  • method of control and direction/position designations.
• Fan types by fluid path: Classifies axial, mixed-flow and centrifugal fans based on blade/shroud geometry and blade angle ranges.
• Annexes and examples: Informative annex with examples and bibliography for further reference.

Applications

• Manufacturers and designers use the standard to label products consistently and to document characteristic dimensions and component parts.
• Engineers and consultants apply the vocabulary when preparing specifications, performing performance testing (in accordance with referenced test standards) and comparing fan types (axial, mixed-flow, centrifugal).
• Procurement and contracting benefit from reduced ambiguity in tender documents and clearer communication of installation categories, fan function and suitability for operating conditions.

Practical benefits: improved interoperability of datasheets, clearer selection criteria, and consistent reporting of fan performance and installation arrangements.

Related Standards

The draft references and aligns with several ISO documents, for example:

• ISO 5167-1 (flow measurement principles)
• ISO 5801 (fan performance testing using standardized airways)
• ISO 5802 (industrial fans - in situ testing)
• ISO/CD 12759-1 (fan efficiency classification)
• ISO 13351 (fan dimensions)

For specification, testing and procurement tasks in ventilation, HVAC and industrial air-handling, prEN ISO 13349 provides the authoritative terminology and categorization needed to ensure consistent communication across manufacturers, engineers and regulators.

Standards Content (Sample)

SLOVENSKI STANDARD
01-september-2021
Ventilatorji - Slovar in definicije kategorij (ISO/DIS 13349:2021)
Fans - Vocabulary and definitions of categories (ISO/DIS 13349:2021)
Ventilatoren - Terminologie und Klassifizierung (ISO/DIS 13349:2021)
Ventilateurs - Vocabulaire et définitions des catégories (ISO/DIS 13349:2021)
Ta slovenski standard je istoveten z: prEN ISO 13349
ICS:
01.040.23 Tekočinski sistemi in sestavni Fluid systems and
deli za splošno rabo (Slovarji) components for general use
(Vocabularies)
23.120 Zračniki. Vetrniki. Klimatske Ventilators. Fans. Air-
naprave conditioners
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT INTERNATIONAL STANDARD
ISO/DIS 13349
ISO/TC 117 Secretariat: BSI
Voting begins on: Voting terminates on:
2021-07-16 2021-10-08
Fans — Vocabulary and definitions of categories
Ventilateurs — Vocabulaire et définitions des catégories
ICS: 23.120; 01.040.23
THIS DOCUMENT IS A DRAFT CIRCULATED
This document is circulated as received from the committee secretariat.
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
ISO/CEN PARALLEL PROCESSING
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 13349:2021(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
©
PROVIDE SUPPORTING DOCUMENTATION. ISO 2021

ISO/DIS 13349:2021(E)
© ISO 2021
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: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved

ISO/DIS 13349:2021(E)
Contents  Page
Foreword .iv
Introduction .v
1 Scope . 1
2  Normative references . 1
3  Terms and definitions . 1
4  Symbols and units .10
4.1 Symbols .10
4.2 Multiples of primary units .11
4.3 Units of time .11
4.4 Temperature of air or gas .11
5  Fan categories .11
5.1 General .11
5.2 Suitability for the fan pressure .11
5.2.1 Work per unit mass .12
5.2.2 Fan categories.12
5.2.3 Changes in air density .12
5.3 Suitability of construction .12
5.3.1 Categorization according to casing construction .12
5.3.2 Designation for hot-gas fan .13
5.3.3 Designation and recommended categorization for smoke-ventilating fans .13
5.3.4 Categorization for gas-tight fans .13
5.4 Transmission arrangements .14
5.5 Inlet and outlet conditions .18
5.6 Method of fan control .18
5.7 Designation of direction of rotation and position of parts of the fan assembly .19
5.7.1 General.19
5.7.2 Direction of rotation .19
5.7.3 Outlet position of a centrifugal fan .19
5.7.4 Position of component parts of a centrifugal fan with volute casing .19
5.7.5 Position of component parts of an axial-flow, mixed-flow or other fan with
coaxial inlet and outlet .20
5.7.6 Position of motor or other prime mover .20
5.8 Characteristic dimensions and component parts .20
5.8.1 Characteristic dimensions .20
5.8.2 Terms for fan component parts .20
Annex A (informative) Examples .42
Bibliography .44
ISO/DIS 13349:2021(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International
Standards adopted by the technical committees are circulated to the member bodies for voting.
Publication as an International Standard requires approval by at least 75 % of the member bodies
casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 13349 was prepared by Technical Committee ISO/TC 117, Fans.
This second edition cancels and replaces the first edition (ISO 13349:2010), which has been technically
revised.
iv © ISO 2021 – All rights reserved

ISO/DIS 13349:2021(E)
Introduction
This International Standard reflects the importance of a standardized approach to the terminology of
fans.
The need for an International Standard has been evident for some considerable time. To take just one
example, the coding of driving arrangements differs from manufacturer to manufacturer. What one
currently calls arrangement no. 1 can be known by another as arrangement no. 3. The confusion for the
customer is only too apparent. For similar reasons, it is essential to use standardized nomenclature to
identify particular parts of a fan.
Wherever possible, in the interests of international comprehension, this International Standard is in
agreement with similar documents produced by Eurovent, AMCA, VDMA (Germany), AFNOR (France)
and UNI (Italy). They have, however, been built on where the need for amplification was apparent.
Use of this International Standard will lead to greater understanding among all parts of the air-
moving industry. This International Standard is intended for use by manufacturers, consultants and
contractors.
DRAFT INTERNATIONAL STANDARD ISO/DIS 13349:2021(E)
Fans — Vocabulary and definitions of categories
1 Scope
This International Standard defines terms and categories in the field of fans used for all purposes.
It is not applicable to electrical safety.
2  Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 5167-1, Measurement of fluid flow by means of pressure differential devices inserted in circular cross-
section conduits running full — Part 1: General principles and requirements
ISO 5801:2017, Fans — Performance testing using standardized airways
ISO 5802:2001, Industrial fans — Performance testing in situ
ISO/CD 12759-1, Fans — Efficiency classification for fans — Part 1:General information for fans
ISO 13351, Fans — Dimensions
3  Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 5167-1 and ISO 5801 and the
following apply
3.1
Fan
rotary-bladed machine that receives mechanical energy and utilizes it by means of one or more
impellers fitted with blades to maintain a continuous flow of air or other gas passing through it and
whose work per unit mass does not normally exceed 25 kJ/kg
Note 1 to entry: The term “fan” is taken to mean the fan as supplied, without any addition to the inlet or outlet,
except where such addition is specified.
Note 2 to entry: Fans are defined according to their installation category, function, fluid path and operating
conditions.
Note 3 to entry: If the work per unit mass exceeds a value of 25 kJ/kg, the machine is termed a turbocompressor.
This means that, for a mean stagnation density through the fan of 1,2 kg/m , the fan pressure does not
exceed 1,2 × 25 kJ/kg, i.e. 30 kPa, and the pressure ratio does not exceed 1,30 since atmospheric pressure is
approximately 100 kPa.
3.1.1
non-driven Fan
a fan without motors, drives, attachments or accessories
Note 1 to entry: Also known as Bare Shaft Fan.
See ISO 12759-1.
ISO/DIS 13349:2021(E)
3.1.2
driven fan
a fan driven by an electrical motor. One or more impellers fitted to or connected to a motor with a
stationary element, with or without transmission or variable speed drive.
[SOURCE: See ISO 12759-1.]
3.1.3
fan integrated (embedded) in other energy related products
fan which is an integral part of another product
3.1.4
term for Stand Alone Fan
a fan what is used as a unique entity and integrated into any other product, it may or may not have
ducting connected to its inlet and outlet
3.2
Air
abbreviated term for the expression “air or other gas”
3.3
Standard air
by convention, air with a density of 1,2 kg/m
3.4  Fan installation categories according to the arrangement of ducting
[SOURCE: See Figure 1.]
3.4.1
installation category A
installation with free inlet and free outlet with a partition
[SOURCE: See ISO 5801 and ISO 5802.]
3.4.2
installation category B
installation with free inlet and ducted outlet
[SOURCE: See ISO 5801 and ISO 5802.]
3.4.3
installation category C
installation with ducted inlet and free outlet
[SOURCE: See ISO 5801 and ISO 5802.]
3.4.4
installation category D
installation with ducted inlet and ducted outlet
[SOURCE: See ISO 5801 and ISO 5802.]
3.4.5
installation category E
installation with free inlet and free outlet without a partition
3.5  Types of fan according to their development and application
3.5.1
custom designed fan
fan developed and produced for one single application
2 © ISO 2021 – All rights reserved

ISO/DIS 13349:2021(E)
3.5.2
standardised fan
fan whose detailed performance is widely available in a catalogue (electronic and/or printed),and
which is frequently manufactured in quantity
3.6  Types of fan according to their function
3.6.1
ducted fan
fan used for moving air within a duct
Note 1 to entry: This fan can be arranged in installation category B, C or D (see Figures 3, 4, 5 and 6).
3.6.2
partition fan
fan used for moving air from one free space to another, separated from the first by a partition having an
aperture in which or on which the fan is installed
Note 1 to entry: This fan can be arranged in installation category A (see Figure 7).
3.6.3
jet fan
fan used for producing a jet of air in a space and unconnected to any ducting
[SOURCE: See Figure 8.]
Note 1 to entry: The air jet can be used, for example, for adding momentum to the air within a duct, a tunnel or
other space, or for intensifying the heat transfer in a determined zone.
3.6.4
circulating fan
fan used for moving air within a space which is unconnected to any ducting
[SOURCE: See Figure 9.]
3.6.5
air curtain unit
air moving device which produces an air curtain
[SOURCE: See Figure 31.]
3.6.5.1
air curtain
airstream
directionally controlled airstream, moving across the entire height and width of an opening, which can
reduce the infiltration or transfer of air from one side of the opening to the other, and inhibits insects,
dust or debris from passing through
3.7  Fan types according to the fluid path within the impeller
fan of specific and typical design primarily distinguished by the geometry of its impeller and the
resulting gas path through the fan
3.7.1
axial, mixed flow and centrifugal fan
fan types are identified by the angles α, average value of the angles α1 and α2 (see Figure 2)
α = (α1 + α2)/2
ISO/DIS 13349:2021(E)
The angle α1 is the angle of the tangent at the hub at the intersection of the blade trailing edge with the
hub. The angle α2 is the angle of the tangent at the shroud or at the outer diameter of the blade at the
intersection of the blade trailing edge with the shroud or with the outer diameter of the blade. If the
hub and/or shroud are not axisymmetric, angles α1 and α2 are the average values in circumferential
direction. The fan types are defined as in Table 1.
Table 1 — Fan type defined by the relationship of the blade and the shroud/hub
Fan type Angle α
Axial fan α < 20°
Mixed flow fan 20° ≤ α < 70°
Centrifugal fan 70° ≤ α
Note 1 to entry: Centrifugal fans contain the types ‘centrifugal radial bladed fan’ (including radial tip), ‘centrifugal
forward curved fan’ and ‘centrifugal backward curved fan’ (including also backward inclined and backward
curved aerofoil bladed fans).
3.7.2
axial fan
axial-flow fan in which the air enters and leaves the impeller along essentially cylindrical surfaces
coaxial with the fan
[SOURCE: See Figure 4.]
Note 1 to entry: An axial-flow fan can be of the low-, medium- or high-pressure type, according to the aspect ratio
of hub diameter to outside impeller diameter. These terms indicate that the pressure generated at a given flow
rate is low, medium or high.
Note 2 to entry: Figure 11 shows a cross-section through a family of impellers having the same outside diameter.
Fans with ratios of hub/outside impeller diameter of less than approximately 0,4 mm are considered “low aspect
ratio”, and greater than approximately 0,71 mm are considered “high aspect ratio”. Medium aspect ratio axial
fans are intermediate between these two figures.
Note 3 to entry: These categories are also affected by the ability to run at the necessary peripheral speed.
3.7.2.1
contra-rotating fan
axial-flow fan which has two impellers arranged in series and rotating in opposite directions
[SOURCE: See Figure 33.]
3.7.2.2
reversible axial-flow fan
axial-flow fan that is specially designed to rotate in either direction, regardless of whether or not the
performance is identical in both directions
3.7.2.3
propeller fan
axial-flow fan having an impeller with a small number of broad blades of uniform material thickness
and designed to operate in an orifice
3.7.2.4
plate-mounted axial-flow fan
axial-flow fan in which the impeller rotates in an orifice or spigot of relatively short axial length, the
impeller blades being of aerofoil section
3.7.2.5
vane-axial fan
axial-flow fan suitable for ducted applications, which has guide vanes before or after the impeller, or
both
4 © ISO 2021 – All rights reserved

ISO/DIS 13349:2021(E)
3.7.2.6
tube-axial fan
axial-flow fan without guide vanes, suitable for ducted applications
3.7.3
mixed-flow fan
fan in which the fluid path through the impeller is intermediate between the centrifugal and axial-flow
types
Note 1 to entry: also known as diagonal flow fan.
[SOURCE: See Figures 6 and 12.]
3.7.4
centrifugal fan
fan in which the air enters the impeller with an essentially axial direction and leaves it in a direction
perpendicular, or near perpendicular to this axis (see Table 1 and Figures 2,3)
Note 1 to entry: The centrifugal fan is also known as a radial-flow fan.
Note 2 to entry: The impeller can have one or two inlet(s) and might include a shroud and/or a backplate
(centreplate) (see Figure 17).
Note 3 to entry: The impeller is defined as “backward-curved or inclined”, “radial” or “forward-curved”,
depending on whether the outward direction of the blade at the periphery is backward, radial or forward relative
to the direction of the rotation (see Figures 10 and 17).
Note 4 to entry: A centrifugal fan can be of the low-, medium- or high-pressure type, according to the aspect ratio
of fan inlet diameter to outside diameter of the impeller. These terms indicate that the pressure generated at a
given flow rate is low, medium or high.
Note 5 to entry: Figure 10 shows a cross-section through a family of impellers having the same inlet diameter.
Fans with ratios of fan inlet/outside impeller diameter of greater than approximately 0,63 mm are considered
“low aspect ratio”, and lower than approximately 0,4 mm are considered “high aspect ratio”. Medium aspect ratio
centrifugal fans are intermediate between these two.
Note 6 to entry: The impeller diameter and the casing scroll radii increase with the pressure range for which the
fan is designed.
Note 7 to entry: These categories are also affected by the ability to run at the necessary peripheral speed (see 5.2
and Table 2).
3.7.5
cross flow fan (tangential fan)
fan in which the fluid path through the impeller is in a direction essentially at right angles to its axis
both entering and leaving the impeller at its periphery
[SOURCE: See Figure 13.]
3.7.6
induced flow fan
housed fan with a nozzle and windband whose outlet airflow is greater than its inlet airflow due to
induced airflow
Note 1 to entry: All of the flow entering the inlet will exit through the nozzle, the flow exiting the windband will
include the nozzle flow plus the induced flow.
Note 2 to entry: Windband can also referred to as an airflow accelerator or venturi.
ISO/DIS 13349:2021(E)
3.7.7
peripheral or side channel fan
air moving device for which the circulation of fluid in the toric casing is helicoidal
Note 1 to entry: The rotation of the impeller, which contains a number of blades, creates a helicoidal trajectory,
which is intercepted by one or more blades depending on the flow rate. The impeller transfers energy to the fluid
(see Figure 16).
3.7.8
multi-stage fan
fan having two or more impellers working in series
EXAMPLE A two-stage fan or a three-stage fan.
Note 1 to entry: Multi-stage fans can have guide vanes and interconnecting ducts between successive impellers.
Note 2 to entry: The blades of an impeller can be either of a profiled section (as an aerofoil) or of uniform
thickness (see Figure 17).
3.7.9
in-line centrifugal fan
fan having a centrifugal impeller used in an in-line ducted configuration
[SOURCE: See Figure 5.]
3.7.10
bifurcated fan
fan having an axial-flow, mixed-flow or centrifugal impeller in an in-line configuration where the direct-
drive motor is separated from the flowing air stream by means of a compartment or tunnel
[SOURCE: See Figure 28 c).]
3.7.11
plug fan
fan having an unhoused impeller arranged such that the system into which it is inserted acts as a
housing, allowing air to be drawn into the impeller inlet
[SOURCE: See Figure 14.]
3.7.12
plenum fan
fan having an unhoused centrifugal impeller which draws air into the impeller through an inlet located
in a barrier wall, and having a driver located on the same side of the barrier as the impeller
[SOURCE: See Figure 15.]
3.7.13
in-line and box fan
fan that incorporates centrifugal/mixed-flow impellers
[SOURCE: See Figures 5 and 31.]
3.8  Types of fan according to operating conditions
3.8.1
general-purpose fan
fan suitable for handling air which is non-toxic, unsaturated, non-corrosive, non-flammable, free from
abrasive particles and within a temperature range from −20 °C to +80 °C
Note 1 to entry: For temperatures greater than 40 °C, the motor is especially taken into consideration.
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ISO/DIS 13349:2021(E)
3.8.2
special-purpose fan
fan used for special operating conditions
[SOURCE: See 3.8.2.1 to 3.8.2.12.]
Note 1 to entry: A fan can have a combination of special features.
Note 2 to entry: The operating conditions stated below (3.8.2.1 to 3.8.2.12) represent a typical range, but the
list is not necessarily complete. It is intended that the manufacturer and purchaser agree on other types having
special features to suit specific applications.
3.8.2.1
hot-gas fan
fan used for handling hot gases continuously
Note 1 to entry: Special materials can be incorporated, as necessary, for the fan which can have a direct or
indirect drive.
Note 2 to entry: The motor on a direct-drive fan can be either in the air stream or separated from it.
Note 3 to entry: Indirect-drive fans can incorporate a means for cooling belts, bearings or other drive components,
where necessary (for designation, see 5.3.2).
3.8.2.2
smoke-ventilating fan
fan suitable for handling hot smoke for a specified time/temperature profile
Note 1 to entry: Special materials can be incorporated, as necessary, for the fan, which can have a direct or
indirect drive.
Note 2 to entry: The motor can be either in the air stream on a direct-drive fan or separated from it.
Note 3 to entry: Indirect-drive fans incorporate a means for cooling belts, bearings or other drive components,
where necessary (for designation, see 5.3.2).
3.8.2.3
wet-gas fan
fan suitable for handling air containing particles of water or any other liquid
3.8.2.4
gas-tight fan
fan with a suitably sealed casing to match a specified leakage rate at a specified pressure
Note 1 to entry: Depending upon the leakage specification, this can involve special attention being paid to all
services which penetrate the casing, such as inspection means, lubricator fittings and electrical supply, as well as
the details of the connecting flanges (for categorization, see 5.3.4).
3.8.2.5
dust fan
fan suitable for handling dust-laden air, designed to suit the dust being handled
3.8.2.6
conveying fan
transport fan
fan suitable for the conveying of solids and dust entrained in the air stream, designed to suit the
material being conveyed
Note 1 to entry: A conveying/transport fan can be of direct or indirect drive type, depending on whether or not
the handled material passes through the impeller.
Note 2 to entry: Examples of solids are wood chips, textile waste and pulverized materials.
ISO/DIS 13349:2021(E)
3.8.2.7
non-clogging fan
fan having an impeller designed to minimize clogging by virtue of its detailed shape or by the use of
special materials
Note 1 to entry: The fan can also incorporate other features to allow the use of cleaning sprays and facilitate the
removal of any material.
3.8.2.8
abrasion-resistant fan
fan designed to minimize abrasion, having parts that are especially subject to wear, constructed from
suitably abrasion-resistant materials and easily replaceable
3.8.2.9
corrosion-resistant fan
fan constructed from suitably corrosion-resistant materials or suitably treated to minimize corrosion
by specified agents
3.8.2.10
spark-resistant fan
ignition-protected fan
fan with features designed to minimize the risk of sparks or hot spots resulting from contact between
moving and stationary parts that may cause the ignition of dust or gases
Note 1 to entry: No bearings, drive components or electrical devices are placed in the air or gas stream, unless
they are constructed in such a manner that failure of that component cannot ignite the surrounding gas stream
(for categorization, see 5.3.4).
3.8.2.11
powered-roof ventilator
fan designed for mounting on a roof and having exterior weather protection
3.8.2.12
positive-pressure ventilator
portable fan that can be positioned relative to an opening of a confined space and cause it to be positively
pressurized by discharge air velocity
Note 1 to entry: It is principally used by fire-fighters to mitigate the effect of smoke and is also used to assist in
inflating hot air balloons.
3.9  Fan elements
3.9.1
fan inlet
opening, usually circular or rectangular, through which the air first enters the fan casing
Note 1 to entry: If the fan is provided with an inlet-connecting flange or spigot, the fan inlet dimensions are
measured inside this connection. The inlet area is the gross area measured inside this flange, i.e. no deductions
are made for blockages, such as motors and bearing supports.
Note 2 to entry: When the inlet area is not clearly defined, agreement can be reached between the parties to the
contract.
3.9.2
fan outlet
opening, usually circular or rectangular, through which the air finally leaves the fan casing
Note 1 to entry: If the fan is provided with an outlet connecting flange or spigot, the fan outlet dimensions are
measured inside this connection. When the fan is delivered with a diffuser and the performance is quoted with
this fitted, the area of the fan outlet can be taken as equal to the outlet area of the diffuser.
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ISO/DIS 13349:2021(E)
Note 2 to entry: When the outlet area is not clearly defined, agreement can be reached between the parties to the
contract.
Note 3 to entry: For the special requirements of jet fans, see ISO 13350.
Note 4 to entry: For roof ventilators and unhoused fans, the outlet area can be considered as the product of
the maximum circumference of trailing edges by the width of the impeller blade or the gross casing area at the
impeller for axial types.
3.9.3
impeller
rotating part of the fan that is imparting energy into the gas flow
3.9.4
impeller tip diameter
maximum diameter measured over the tips of the blades of the impeller
Note 1 to entry: This is expressed in millimetres.
[SOURCE: See ISO 13351.]
3.9.5
stationary element
stationary part which interacts with the air stream passing through the impeller, it is an element, or
a combination of elements, that interacts with the airstream directing and/or guiding the gas steam
towards, through and/or from the impeller, an element may also assist in the conversion of energy
Note 1 to entry: Examples of Stationary Elements are;
• Housing
• Orifice ring
• Orifice panel
• Inlet bell, also known as venturi, inlet cone, inlet radius
• Inlet guide vane
• Outlet guide vane
• Outlet diffuser
• Nozzle
Note 2 to entry: – in some standards a Stationary Element is called a Stator, examples of Stationary Elements are
shown in Annex A.
3.9.6
housing
stationary part which interacts with the air stream passing through the impeller, a housing could be
an element around the impeller which guides the gas stream towards, through and from the impeller, a
housing may have additional parts included within the housing or attached to the housing to an affect
the performance of the fan such as;
• Inlet bell, also known as venturi inlet, inlet cone, inlet radius
• Inlet guide vane
• Outlet guide vane
• Outlet diffuser
ISO/DIS 13349:2021(E)
3.9.7
orifice ring
ring with an opening in which the fan sits and which allows the fan to be fixed to other structures
3.9.8
inlet guide vanes
vanes positioned before the impeller to guide the gas stream towards the impeller and which may or
may not be adjustable
3.9.9
outlet guide vanes
vanes positioned after the impeller to guide the gas stream from the impeller and which may or may
not be adjustable
3.9.10
orifice panel
panel with an opening in which the fan sits and which allows the fan to be fixed to other structures
3.9.11
inlet cone (also known as venturi inlet, inlet bell, inlet radius or inlet ring)
device that steers the air into the housing and reduces the vena contracta and turbulence that would
occur at a sharp edge of the housing
3.9.12
nozzle
apperture or adjutage of the fan through which air or gas is discharged
3.9.13
size designation
nominal impeller tip diameter, defined as the impeller tip diameter on which the design of that fan is
based
4  Symbols and units
4.1 Symbols
The following symbols and primary units for the parameters listed apply.
Parameter Symbol Unit
Volume flow rate q m /s
V
Fan pressure p Pa
F
Power P W
Torque τ Nm
Gas density ρ kg/m
Impeller tip speed u m/s
Outlet or duct velocity v m/s
Rotational frequency n r/s
Rotational speed N r/min
Dimensions — mm
Moment of inertia I kg⋅m
Stress σ Pa
Energy E J
Note 1  For sound units, see ISO 13347-1.
Note 2  For efficiency units, see ISO 5801.
10 © ISO 2021 – All rights reserved

ISO/DIS 13349:2021(E)
Parameter Symbol Unit
Temperature Θ K
Temperature Τ °C
Work per unit mass W J/kg
Thrust (calculated, measured) T , T N
c m
Note 1  For sound units, see ISO 13347-1.
Note 2  For efficiency units, see ISO 5801.
4.2  Multiples of primary units
The choice of the appropriate multiple or submultiple of an SI unit is governed by convenience. The
multiple chosen for a particular application shall be that which leads to numerical values within a
practical range (e.g. kilopascal for pressure, kilowatts for power and megapascal for stress).
4.3  Units of time
The second is the SI base unit of time, although outside SI the minute has been recognized by the
Internal Committee for Weights and Measurements (CIPM) as necessary to be retained for use because
of its practical importance. Manufacturers may, therefore, continue with the use of r/min for rotational
speed.
4.4  Temperature of air or gas
The kelvin is the SI base unit of thermodynamic temperature and is preferred for most scientific and
technological purposes. The degree Celsius (°C) is acceptable for practical applications.
5  Fan categories
5.1 General
Fans may be categorized according to
a) suitability for the fan pressure,
b) suitability of construction (including features required for smoke ventilation, gas tightness and
ignition protection),
c) driving arrangement,
d) inlet and outlet conditions,
e) method of fan control,
f) rotation and position of parts, and
g) characteristic dimensions.
Examples of the use of the definitions and categories to identify a fan in a specification are given in
Annex A.
5.2  Suitability for the fan pressure
A fan may also be defined as being low, medium or high pressure, according to the level of work per unit
mass, and whether the influence of compressibility of the air or gas being handled has to be taken into
account. For a detailed account of these considerations, see ISO 5801.
ISO/DIS 13349:2021(E)
A low-pressure fan is then defined as having a pressure ratio less than 1,02 kPa and a reference Mach
No. of less than 0,15. This corresponds to a pressure rise of less than 2 kPa when handling standard air.
A medium-pressure fan is defined as having a pressure ratio greater than 1,02 kPa and less than 1,1 kPa.
The reference Mach No. shall be less than 0,15. This corresponds to a pressure rise of 2 kPa to 10 kPa.
A high-pressure fan is defined as having a pressure ratio and pressure rise greater than the above-
mentioned.
5.2.1  Work per unit mass
A convention is used for all industrial fans except jet fans (see ISO 13350), denoting the work per unit
mass as the quotient of air power and mass flow rate. The fan pressure is approximately equal to the
product of work per unit mass and the mean stagnation density of the fluid within the fan.
5.2.2  Fan categories
Depending on its peripheral speed, a fan impeller develops more or less pressure. This International
Standard defines a range of “fan categories” where the fan pressure at maximum efficiency and
maximum rotational speed is not less than the value given in Table 1. In any event, this defined fan
pressure (as shown in Table 1) shall not exceed 95 % of the maximum pressure developed by the fan at
its maximum speed.
5.2.3  Changes in air density
These categories shall also be used to indicate whether or not the change in air density within the fan
shall be considered. For a low-pressure fan, this change may be neglected. For a high-pressure fan,
this change shall not be neglected, whereas for a medium-pressure fan, it may or may not be neglected
depending on the desired accuracy. Detailed mechanical design and construction of the rotational
elements are determined by the peripheral speed and, therefore, the pressure for which the fan is
specified. For examples of centrifugal fans, see Figure 10.
Table 2 — Categorization of fan according to fan pressure at maximum safe rotational speed
Maximum fan pressure
(for standard air)
Fan description Code Category
kPa
Low pressure L > 0 and ≤ 0,7 0
> 0,7 and ≤ 1 1
> 1 and ≤ 1,6 2
> 1,6 and ≤ 2,0 3
Medium pressure M > 2,0 and ≤ 3,6 4
> 3,6 and ≤ 6,3 5
> 6,3 and ≤ 10 6
High pressure H > 10 and ≤ 16 7
> 16,0 and ≤ 22,4 8
> 22,4 and ≤ 30 9
5.3  Suitability of construction
5.3.1  Categorization according to casing construction
Fans are used for a variety of purposes (see 3.8). The air or gas handled may be clean or contain
moisture or solid particles and may be at ambient or other temperature. Connection to its associated
12 © ISO 2021 – All rights reserved

ISO/DIS 13349:2021(E)
ducting can be via flexible elements or alternatively it may be attached directly, such that the casing
has to withstand additional loads due to the dead weight of these connections. Where a high or low
temperature is present, further loading can result from the effects of expansion or contraction. Casing
thickness and stiffening are also determined by the ability to withstand the specified fan pressure and
dynamic loads and by the need for a margin to counter the effects of any erosion or corrosion. For all
these and other reasons, different methods of casing construction and different casing thicknesses are
appropriate to the application.
The categorization in Table 3 reflects current practice and shall be used only to assist specification. It
in no way indicates any form of grading. Category 1 is as valid for clean air ventilation as Category 3 is
preferred for heavy industrial requirements.
Table 3 — Categorization of fan according to method of casing construction
Casing thick-
Category Typical casing features Usage
ness
1 Lockformed, spot welded or screwed construc- — Light HVAC clean air < 0,002 5D
tion. Cradle or angle frame mounting
2 Lockformed, seam welded or continuously — Heavy HVAC > 0,002 5D
welded construction. Semi-universal design
— Light industrial
with bolted on side-plates
— Light dust or moisture
3 Fully welded fixed discharge — Heavy industrial > 0,003 33D
— Dirty air containing
moisture or solids, or
— High pressure or
— High power
NOTE  D is the nominal impeller diameter, in millimetres.
5.3.2  Designation for hot-gas fan
Where a fan is suitable for continuous operation up to a stated maximum temperature (for hot-gas fan,
see 3.8.2.1), this should be indicated on the conventional fan rating plate itself.
The designation that shall be used is: T, followed by the maximum temperature in degrees Celsius (°C),
for continuous operation.
EXAMPLE T/500 denotes a fan rated for a maximum continuous temperature of 500 °C.
5.3.3  Designation and recommended categorization for smoke-ventilating fans
If the fan is also, or only, capable of short-term operation at a high temperature, this information shall
be clearly stated on a separate label (see 3.8.2.2).
5.3.4  Categorization for gas-tight fans
Gas-tight fans shall be categorized in accordance with Table 4 (see 3.8.2.4). The amount of leakage is
dependent on the pressure within the fan casing and the time for which this must be maintained. The
leakage rate is obtained by blocking off the fan inlet and outlet and “pumping up” or extracting the
casing using an auxiliary test fan. The change in the test pressure shall be measured by a manometer as
a function of time. The leakage rate is then determined from the flow of the auxiliary test fan or other
pressure sources. This leakage shall be less than the value calculated from the formula appropriate to
the category.
ISO/DIS 13349:2021(E)
Normally, the fan is stationary during this test. However, if the correct functioning of the shaft seal is
dependent on fan rotation, the test shall be carried out with the impeller removed and the remainder of
the fan running.
Categories A to D match the established classes of allowable ductwork leakage rate used in the air-
conditioning industry. Category E is often specified for systems handling toxic fumes, while categories F
and G relate to nuclear and defence equipment specifications, respectively.
Table 4 — Categorization of gas-tight fans — Leakage as a function of test pressure
Maximum test pres- Time at maximum
Acceptance criteria/maximum leak-
sure pressure
Leakage category
age rate
kPa min
0,65
A 0,5 15 0,027 × p
0,65
B 1 15 0,009 × p
0,65
C 2 15 0,003 × p
0,65
D 2,5 15 0,001 × p
0,65
E 2,5 15 0,000 5 × p
F 3 60 Fall in p < 500 Pa
G 10,5 15 No detectable leaks
H1 1,5 60 Fall in p < 150 Pa
H2 1,5 60 Fall in p < 15 Pa
NOTE 1  Leakage rates in categories A, B, C, D and E are in litres per second per square metre of casing wetted area and p is
the test pressure in pascals.
NOTE 2  Leakage is defined as loss of pressure in categories F, H1 and H2. Especially when measuring the pressure loss
according to leakage categories H1 or H2, attention has to be drawn to changes of the gas temperature inside the casing or
the ambient pressure during measurement as they can taint the result significantly.
5.4  Transmission arrangements
The six most commonly used types of transmission are the following.
a) Direct transmission from the shaft of the motor or other prime mover: the impeller is fixed to the
shaft extension.
b) Transmission through an in-line direct coupling: the transmission shaft and the impeller shaft are
each fixed on a part of the in-line direct coupling and rotate at the same speed.
c) Transmission through an in-line slipping coupling: the transmission shaft is fixed to the primary
part of the coupling and the impeller shaft to the secondary part of the coupling, enabling them to
rotate at different speeds, the relative difference of which (i.e. the slip) depends upon the speed, the
torque to be transmitted and, when appropriate, the degree of control applied to the coupling.
d) Transmission through
...