ISO 7240-20:2010

Fire detection and alarm systems - Part 20: Aspirating smoke detectors

ISO 7240-20:2010 specifies the requirements, test methods and performance criteria for aspirating smoke detectors for use in fire detection and alarm systems installed in buildings. Aspirating smoke detectors developed for the protection of specific risks that incorporate special characteristics (including additional features or enhanced functionality for which ISO 7240-20:2010 does not define a test or assessment method) are also covered by ISO 7240-20:2010. The performance requirements for any special characteristics are beyond the scope of ISO 7240-20:2010.

Systèmes de détection et d'alarme d'incendie — Partie 20: Détecteurs de fumée par aspiration

General Information

• Status: Published
• Publication Date: 10-May-2010
• ICS: 13.220.20 - Fire protection
• Technical Committee: ISO/TC 21/SC 3 - Fire detection and alarm systems
• Drafting Committee: ISO/TC 21/SC 3 - Fire detection and alarm systems
• Current Stage: 9093 - International Standard confirmed
• Start Date: 02-Nov-2021
• Completion Date: 13-Dec-2025

Overview - ISO 7240-20:2010 (Aspirating smoke detectors)

ISO 7240-20:2010 is the international standard that specifies requirements, test methods and performance criteria for aspirating smoke detectors (a.s.d.) used in building fire detection and alarm systems. It covers design verification, environmental and EMC testing, classification by sensitivity, and the definition of key terms such as sampling device, transport time and response threshold value (RTV). The part is based on EN 54‑20 and addresses both general-purpose aspirating detectors and units developed for specific risks (special characteristics are covered but their bespoke performance requirements are out of scope).

Key topics and technical requirements

• Scope and compliance: mandatory clauses for inspection, engineering assessment and laboratory testing to demonstrate conformity.
• Classification and sensitivity: devices are classified by fire sensitivity (three sensitivity classes are defined) and are tested using representative test fires (TF2–TF5 family).
• Sampling system: requirements for sampling devices and sampling points, transport time and mechanical strength of pipework.
• Detection performance: definition of response threshold value (RTV) - aerosol concentration at alarm - and fire sensitivity test methods.
• Environmental & EMC tests: dry heat, cold, damp heat, vibration, shock, SO2 corrosion and electromagnetic compatibility (EMC) immunity tests (references to IEC/EN test methods are given).
• Airflow monitoring & power: monitoring of sample airflow and robustness of power-supply arrangements.
• Hardware & software: requirements for additional sensing elements, marking, data documentation and added provisions for software-controlled detectors.
• Test documentation: required content of test reports and informative/normative annexes that describe test fires and test-room apparatus.

Practical applications

• Early-warning detection in high-value or sensitive environments such as clean rooms, data centers, HVAC ducts and critical infrastructure where very dilute smoke must be detected.
• Protection of specialized risks where aspirating networks sample remote spaces or concealed voids.
• Use cases requiring monitored sampling lines and known transport times (e.g., long pipe networks or ducts).

Who should use this standard

• Manufacturers of aspirating smoke detectors - for product design, testing and declarations.
• System designers and installers - to select appropriate detector class and sampling schemes.
• Testing laboratories and certification bodies - for type testing and conformity assessment.
• Fire safety engineers, specifiers and authorities having jurisdiction - for specifying interoperable, validated detection solutions.

Related standards

• ISO 7240 series (e.g., ISO 7240‑1, ISO 7240‑7, ISO 7240‑4)
• EN 54‑20 (basis for this part)
• IEC 60068 environmental test series and EN 50130‑4 (EMC immunity)

Keywords: ISO 7240-20:2010, aspirating smoke detectors, fire detection and alarm systems, response threshold value, sampling device, fire sensitivity tests, airflow monitoring.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 7240-20
First edition
2010-05-15
Fire detection and alarm systems —
Part 20:
Aspirating smoke detectors
Systèmes de détection et d'alarme d'incendie —
Partie 20: Détecteurs de fumée par aspiration

Reference number
©
ISO 2010
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ii © ISO 2010 – All rights reserved

Contents Page
Foreword .v
Introduction.vii
1 Scope.1
2 Normative references.1
3 Terms, definitions and abbreviated terms.2
3.1 Terms and definitions .2
3.2 Abbreviated terms .2
4 Requirements.3
4.1 Compliance .3
4.2 Classification .3
4.3 Individual visual alarm indication.3
4.4 Connection of ancillary devices .3
4.5 Manufacturer's adjustments.3
4.6 On-site adjustment of response behaviour .4
4.7 Response to slowly developing fires .4
4.8 Mechanical strength of the pipework .4
4.9 Hardware components and additional sensing elements in the sampling device.5
4.10 Airflow monitoring.5
4.11 Power supply .5
4.12 Marking.6
4.13 Data.6
4.14 Additional requirements for software controlled detectors.7
5 Tests .8
5.1 General .8
5.2 Repeatability .11
5.3 Reproducibility .11
5.4 Variation in supply parameters.12
5.5 Dry heat (operational) .13
5.6 Cold (operational).14
5.7 Damp heat, steady state (operational) .15
5.8 Damp heat, steady state (endurance).16
5.9 Sulfur dioxide (SO ) corrosion (endurance).17
5.10 Shock (operational) .18
5.11 Impact (operational) .19
5.12 Vibration, sinusoidal (operational) .20
5.13 Vibration, sinusoidal (endurance) .21
5.14 Electromagnetic compatibility (EMC) immunity tests .22
5.15 Fire sensitivity .23
5.16 Mechanical strength of pipe.26
6 Test report.26
Annex A (informative) Apparatus for response threshold value measurements.27
Annex B (normative) Smouldering (pyrolysis) wood fire (TF2) .32
Annex C (normative) Reduced smouldering pyrolysis wood fires (TF2A and TF2B).34
Annex D (normative) Glowing smouldering cotton fire (TF3) .36
Annex E (normative) Reduced glowing smouldering cotton fire (TF3A and TF3B).38
Annex F (normative) Flaming plastics (polyurethane) fire (TF4) .40
Annex G (normative) Flaming liquid (n-heptane) fire (TF5) .42
Annex H (normative) Reduced flaming liquid (n-heptane) fire (TF5A and TF5B).43
Annex I (normative) Fire test room and ventilation system.45
Annex J (informative) Information concerning the requirements for the response to slowly
developing fires .48
Annex K (informative) Apparatus for airflow monitoring test .52
Bibliography .54

iv © ISO 2010 – All rights reserved

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 7240-20 was prepared by Technical Committee ISO/TC 21, Equipment for fire protection and fire fighting,
Subcommittee SC 3, Fire detection and alarm systems.
ISO 7240 consists of the following parts, under the general title Fire detection and alarm systems:
⎯ Part 1: General and definitions
⎯ Part 2: Control and indicating equipment
⎯ Part 3: Audible alarm devices
⎯ Part 4: Power supply equipment
⎯ Part 5: Point-type heat detectors
⎯ Part 6: Carbon monoxide fire detectors using electro-chemical cells
⎯ Part 7: Point-type smoke detectors using scattered light, transmitted light or ionization
⎯ Part 8: Carbon monoxide fire detectors using an electro-chemical cell in combination with a heat sensor
⎯ Part 9: Test fires for fire detectors [Technical Specification]
⎯ Part 10: Point-type flame detectors
⎯ Part 11: Manual call points
⎯ Part 12: Line type smoke detectors using a transmitted optical beam
⎯ Part 13: Compatibility assessment of system components
⎯ Part 14: Guidelines for drafting codes of practice for design, installation and use of fire detection and fire
alarm systems in and around buildings [Technical Report]
⎯ Part 15: Point type fire detectors using scattered light, transmitted light or ionization sensors in
combination with a heat sensor
⎯ Part 16: Sound system control and indicating equipment
⎯ Part 17: Short-circuit isolators
⎯ Part 18: Input/output devices
⎯ Part 19: Design, installation, commissioning and service of sound systems for emergency purposes
⎯ Part 20: Aspirating smoke detectors
⎯ Part 21: Routing equipment
⎯ Part 22: Smoke-detection equipment for ducts
⎯ Part 24: Sound-system loudspeakers
⎯ Part 25: Components using radio transmission paths
⎯ Part 27: Point-type fire detectors using a scattered-light, transmitted-light or ionization smoke sensor, an
electrochemical-cell carbon-monoxide sensor and a heat sensor
⎯ Part 28: Fire protection control equipment
A part 23, dealing with visual alarm devices, is under preparation.

vi © ISO 2010 – All rights reserved

Introduction
This part of ISO 7240 is based on a European Standard EN 54-20:2006, prepared by the European
Committee for Standardization CEN/TC 72 “Fire detection and fire alarm systems”. It has been reviewed and
revised by ISO/TC 21/SC 3/WG 21.
Aspirating smoke detectors differ from point-type smoke detectors (see ISO 7240-7) in that air is drawn into
the smoke-sensing chamber, rather than relying on convection.
This part of ISO 7240 is not intended to place any other restriction on the design and construction of such
detectors.
INTERNATIONAL STANDARD ISO 7240-20:2010(E)

Fire detection and alarm systems —
Part 20:
Aspirating smoke detectors
WARNING — Certain types of detectors contain radioactive materials. National requirements for
radiation protection differ from country to country and they are not, therefore, specified in this part of
ISO 7240.
1 Scope
This part of ISO 7240 specifies the requirements, test methods and performance criteria for aspirating smoke
detectors for use in fire detection and alarm systems installed in buildings.
Aspirating smoke detectors developed for the protection of specific risks that incorporate special
characteristics (including additional features or enhanced functionality for which this part of ISO 7240 does not
define a test or assessment method) are also covered by this part of ISO 7240. The performance
requirements for any special characteristics are beyond the scope of this part of ISO 7240.
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 7240-1, Fire detection and alarm systems — Part 1: General and definitions
ISO 7240-4, Fire detection and alarm systems — Part 4: Power supply equipment
ISO 7240-7:2003, Fire detection and fire alarm systems — Part 7: Point-type smoke detectors using scattered
light, transmitted light or ionization
EN 50130-4:1995 + Amendment 1:1998 + Amendment 2:2003, Alarm systems — Part 4: Electromagnetic
compatibility — Product family standard: Immunity requirements for components of fire, intruder and social
alarm systems
IEC 60068-2-1, Environmental testing — Part 2-1: Tests — Test A: Cold
IEC 60068-2-2, Environmental testing — Part 2-2: Tests — Test B: Dry heat
IEC 60068-2-6, Environmental testing — Part 2-6: Tests — Test Fc: Vibration (sinusoidal)
IEC 60068-2-27, Environmental testing — Part 2-27: Tests — Test Ea and guidance: Shock
IEC 60068-2-42, Environmental testing — Part 2-42: Tests — Test Kc: Sulphur dioxide test for contacts and
connections
IEC 60068-2-75, Environmental testing — Part 2-75: Tests — Test Eh: Hammer tests
IEC 60068-2-78, Environmental testing — Part 2-78: Tests — Test Cab: Damp heat, steady state
IEC 61386-1:2008, Conduit systems for cable management — Part 1: General requirements
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 7240-1 and the following apply.
3.1.1
aspirating smoke detector
smoke detector, in which air and aerosols are drawn through a sampling device and carried to one or more
smoke-sensing elements by an integral aspirator (e.g. fan or pump)
NOTE Each smoke sensing element may contain more than one sensor exposed to the same smoke sample.
3.1.2
response threshold value
measure of the aerosol concentration in the proximity of the smoke sensing element at the moment that the
specimen generates an alarm signal, when it is tested as described in 5.1.5
3.1.3
sampling device
component or series of components or a dedicated device (e.g. a pipe network, dedicated duct, probe or
hood) which forms part of the a.s.d. and transfers samples of air to the smoke sensing element(s)
NOTE The sampling device may be supplied separately.
3.1.4
sampling point
any point at which an air sample is drawn into the sampling device
3.1.5
transport time
time for aerosols to transfer from a sampling point to the smoke sensing element
3.2 Abbreviated terms
For the purposes of this document, the following abbreviations apply.
a.s.d. aspirating smoke detector
c.i.e. control and indicating equipment
c.p.c. condensation particle counter
EMC electromagnetic compatibility
MIC measuring ionization chamber
r.t.v. response threshold value
2 © ISO 2010 – All rights reserved

4 Requirements
4.1 Compliance
To comply with this part of ISO 7240, the detector shall meet the requirements of Clause 4, which shall be
verified by inspection and engineering assessment, and when tested in accordance with the tests described in
Clause 5, shall meet the requirements of the tests.
4.2 Classification
The manufacturer shall clearly state, in accordance with the data presented in 4.13, to which class or classes
the aspirating smoke detector is designed. To demonstrate compliance with a specific class, the aspirating
smoke detector shall be subjected to the appropriate fire sensitivity test as defined in 5.15.
NOTE Due to the differences and many variations in the design of sampling devices, aspirating smoke detectors are
generally intended for use in many varied and often rather specialized applications. Therefore, it might not be practical to
conduct type tests that define acceptance criteria for all of these applications. However, in recognition of the diversity of
application, three classes are defined to enable system designers and installers to select the most appropriate sensitivity.
Table 1 identifies the classes of detector and the corresponding fire tests used for the classification.
Table 1 — Classification of aspirating smoke detectors
Class Description Example application(s) Test fires
A Aspirating smoke detector Very early detection: the detection of very dilute smoke, for TF2A, TF3A, TF4
providing very high sensitivity example entering air conditioning ducts, to detect the and TF5A
extremely dilute concentrations of smoke that can emanate
from equipment in an environmentally controlled area such
as a clean room
B Aspirating smoke detector Early detection: for example, special fire detection within or TF2B, TF3B, TF4
providing enhanced close to particularly valuable, vulnerable or critical items and TF5B
sensitivity such as computer or electronic equipment cabinets
C Aspirating smoke detector Standard detection: general fire detection in normal rooms or TF2, TF3, TF4 and
providing normal sensitivity spaces, giving, for example, at least an equivalent level of TF5
detection as a point- or beam-type smoke detection system
4.3 Individual visual alarm indication
Each aspirating smoke detector shall be provided with integral red visual indicator(s), visible from outside the
aspirating smoke detector, by which the individual smoke-sensing element(s) (see 3.1.1) that released an
alarm can be identified until the alarm condition is reset. Where other conditions of the detector can be visually
indicated, they shall be clearly distinguishable from the alarm indication.
4.4 Connection of ancillary devices
The detector may provide for connections to ancillary devices (e.g. remote indicators, control relays). Open- or
short-circuit failures of these connections shall not prevent the correct operation of the detector.
4.5 Manufacturer's adjustments
It shall not be possible to change the manufacturer's settings except by special means (e.g. the use of a
special code or tool) or by breaking or removing a seal.
4.6 On-site adjustment of response behaviour
NOTE 1 The effective response behaviour of an aspirating smoke detector is dependent upon both the sensitivity
settings of the smoke sensing element and the design of the sampling device. Many types of aspirating smoke detectors,
therefore, have facilities to adjust the smoke-sensing element sensitivity to suit the application and sampling device, etc.
If there is provision for field-adjustment of the sensitivity of the smoke sensing element, then
a) access to the means of adjustment shall be limited by the requirement for the use of tools or a special
code;
b) it shall be possible to determine what sensitivity settings have been selected and to relate these to
documentation that describes the sensitivity settings required for different sampling devices and
applications;
NOTE 2 These adjustments may be made at the detector or at the c.i.e.
NOTE 3 Changing sensitivity settings may affect the classification of the installed a.s.d. – see 4.2.
c) if it is possible to configure the detector (including the sampling device and the sensitivity settings) in such
a way that the detector does not comply with this part of ISO 7240, it shall be clearly marked on the
detector or in the associated data that, if such configurations are used, the detector does not comply with
this part of ISO 7240.
4.7 Response to slowly developing fires
The provision of “drift compensation” (e.g. to compensate for sensor drift due to the build-up of dirt in the
detector) and/or the provision of algorithms to match a detector to its environment shall not lead to a
significant reduction in the sensitivity of the detector to slowly developing fires.
Because it is not practical to carry out tests with very slow increases in smoke density, an assessment of the
response of the detector to slow increases in smoke density shall be made by analysis of the circuit/software,
and/or physical tests and simulations.
Where such algorithms are used, the detector shall be deemed to meet the requirements of 4.7 if the
documentation and assessment shows
a) how and why a sensor drifts;
b) how the compensation technique modifies the detector response to compensate for the drift;
c) that suitable limits to the compensation are in place to prevent the algorithms/means from being applied
outside the known limitations of the sensor and to ensure ongoing compliance with the provisions of this
part of ISO 7240;
d) for any rate of increase in smoke density, R, that is greater than A/4 per hour (where A is the initial
uncompensated r.t.v. of the a.s.d.), the time for the detector to give an alarm does not exceed 1,6 × A/R
by more than 100 s;
e) that the range of compensation is limited such that, throughout this range, the compensation does not
cause the r.t.v. of the detector to exceed its initial value by a factor greater than 1,6.
NOTE Further information about the assessment of requirements d) and e) is given in Annex J.
4.8 Mechanical strength of the pipework
Sampling pipes and fittings shall have adequate mechanical strength and temperature resistance.
Pipes shall either be classified in accordance with IEC 61386-1:2008 to at least class 1131 (for the
significance of the digits, see Table 2) or shall be tested in accordance with 5.16.
4 © ISO 2010 – All rights reserved

Table 2 — Mechanical requirements of sampling pipe
Property Class Severity
Resistance to compression 1 125 N
Resistance to impact 1 0,5 kg, 100 mm height to fall
Temperature range 31 −15 °C to +60 °C

Where the supplier of the a.s.d. does not supply pipes for the sampling device, the product documentation
shall specify that the requirements of this subclause shall be met.
4.9 Hardware components and additional sensing elements in the sampling device
Components, including optional components (box, filter, sensor, valve, etc.), in the sampling device shall be
described in the documentation. The a.s.d., including the hardware components listed (i.e. the worst-case
combination in accordance with the manufacturer's documentation), shall meet the requirements of this part of
ISO 7240.
If the component incorporates a sensing element that participates in the signal output of the a.s.d. (e.g. for
localization information), then the performance of the a.s.d., including these sensing elements, shall meet the
requirements of this part of ISO 7240.
4.10 Airflow monitoring
4.10.1 The airflow through the aspirating smoke detector shall be monitored to detect leakage or obstruction
of the sampling device or sampling point(s).
4.10.2 A fault signal shall be given when the airflow is outside the operational limits as specified by the
manufacturer's data.
A fault signal shall be given for the following:
a) when any leakage or obstruction results in an increase or decrease in the volumetric airflow of 20 % and
greater through an aspirating smoke detector; or
b) when, for aspirating smoke detectors that incorporate technology that provides for constant (or nearly
constant) volumetric flow rate, which is largely independent of the sampling device (e.g. incorporates
speed control of the fan or uses a positive displacement pump), there is a loss of 50 % or more of
sampling points.
In either case, the fault signal shall be released within not more than 300 s of the fault occurring.
NOTE This time is independent of any delay times between signalling the fault and its indication at the c.i.e. and
compensates for spurious, short-term flow variations that would otherwise result in an unwanted fault signal.
4.10.3 Where an a.s.d. has a facility to memorize the “normal” flow rate (present when the detector is
installed or serviced) and, thereafter, monitor for deviations from this normal flow, the action of setting the
memorized “normal” flow shall be a voluntary action at access level 3 (see ISO 7240-2).
4.10.4 Power cycling of the a.s.d. (turning it off and on) shall not result in a change to the memorized
“normal” flow rate.
4.11 Power supply
The power for the aspirating detector shall be supplied by power supply equipment in accordance with
ISO 7240-4. This power supply equipment may be common to the c.i.e.
4.12 Marking
Each detector shall be clearly marked with the following information:
a) number of this part of ISO 7240, e.g. “This product conforms to ISO 7240-20”;
b) name or trademark of the manufacturer or supplier;
c) model designation (type or number);
d) wiring terminal designations;
e) some mark(s) or code(s) (e.g. a serial number or batch code) by which the manufacturer can identify at
least the date or batch and place of manufacture, and the version number(s) of any software contained
within the detector.
Where the sensitivity class (see 4.2) is marked on the detector, additional information shall be provided to
clearly indicate the means by which the classification of any used configuration can be determined.
This additional information may be a cross-reference to a separate document or may be a summary of the
worst-case configuration tested under each class.
Where any marking on the device uses symbols or abbreviations not in common use, these shall be explained
in the data supplied with the device.
The markings shall be visible during installation and shall be accessible during maintenance.
The markings shall not be placed on screws or other easily removable parts.
4.13 Data
Either an aspirating smoke detector shall be supplied with sufficient technical, installation and maintenance
data to enable its correct installation, sensitivity setting and operation or, if all of these data are not supplied
with each a.s.d., reference to the appropriate data sheet(s) shall be given on, or with, each aspirating smoke
detector.
The manufacturer shall declare in these data the classification of each sampling device configuration and
associated sensitivity settings. If the number of configurations is undetermined, the manufacturer shall provide
the necessary means to determine the classification of any configuration used.
These data shall also be available on the commercial datasheets to enable the correct design of an
installation prior to delivery of the hardware.
These data shall be referred to in the test report and shall be used to describe and determine the worst-case
configuration(s) that are used in the fire tests (see 5.15) and the transport time for the sampling point(s) in the
fire test room.
The transport time should not include any processing time and is specifically limited to the time required to
transport aerosols from the sampling point (in the fire test room) to the sensing element.
The method used for determining the classification shall be clearly stated. This is likely to take into account
the following parameters:
a) sizes and number of sampling points (maximum and minimum) and any limitations on their position along
the sampling device;
b) sensitivity settings for the detector and how this parameter should be adjusted;
c) details of permitted sampling device arrangement (e.g. single pipe, branch, “H”-configurations);
6 © ISO 2010 – All rights reserved

d) maximum length of the sampling device (e.g. the maximum pipe length and branch length);
e) aspirator setting (if adjustable).
4.14 Additional requirements for software controlled detectors
4.14.1 General
For detectors that rely on software control to fulfil the requirements of this part of ISO 7240, the requirements
of 4.14.2, 4.14.3 and 4.14.4 shall be met.
4.14.2 Software documentation
4.14.2.1 The manufacturer shall submit documentation to the testing authority that gives an overview of
the software design. This documentation shall be in sufficient detail to allow inspection of the design for
compliance with this part of ISO 7240 and shall include at least the following:
a) functional description of the main program flow (e.g. as a flow diagram or structogram), including
1) a brief description of the modules and the functions that they perform,
2) the manner in which the modules interact,
3) the overall hierarchy of the program,
4) the manner in which the software interacts with the hardware of the detector,
5) the manner in which the modules are called, including any interrupt processing;
b) description of which areas of memory are used for the various purposes (e.g. the program, site-specific
data and running data);
c) designation by which the software and its version can be uniquely identified.
4.14.2.2 The manufacturer shall prepare and maintain detailed design documentation. This shall be
available for inspection in a manner that respects the manufacturer's rights of confidentiality. It shall comprise
at least the following:
a) overview of the whole system configuration, including all software and hardware components;
b) description of each module of the program, containing at least
1) the name of the module,
2) a description of the tasks performed,
3) a description of the interfaces, including the type of data transfer, the valid data range and the
checking for valid data;
c) full source code listings, as hard copy or in a machine-readable form (e.g. ASCII-code), including global
and local variables, constants and labels used, and sufficient comment to recognize the program flow;
d) details of any software tools used in the design and implementation phase (e.g. CASE-Tools, Compilers).
This detailed design documentation may be reviewed at the manufacturer's premises.
4.14.3 Software design
To ensure the reliability of the detector, the following requirements for software design shall apply.
a) Design of the interfaces for manually and automatically generated data shall not permit invalid data to
cause error in the program operation.
b) The software shall be designed to avoid the occurrence of deadlock of the program flow.
4.14.4 The storage of programs and data
The program necessary to comply with this part of ISO 7240 and any pre-set data, such as manufacturer's
settings, shall be held in non-volatile memory. Writing to areas of memory containing this program and data
shall be possible only by the use of some special tool or code and shall not be possible during normal
operation of the detector.
Site-specific data shall be held in memory that can retain data for at least two weeks without external power to
the detector, unless provision is made for the automatic renewal of such data, following loss of power, within
1 h of power being restored.
5 Tests
5.1 General
5.1.1 Atmospheric conditions for tests
Unless otherwise specified in a test procedure, the testing shall be carried out after the test specimen has
been allowed to stabilize in the standard atmospheric conditions for testing described in IEC 60068-1 as
follows:
⎯ temperature: (15 to 35) °C;
⎯ relative humidity: (25 to 75) %;
⎯ air pressure: (86 to 106) kPa.
The temperature and humidity shall be substantially constant for each environmental test where the standard
atmospheric conditions are applied.
5.1.2 Operating conditions for tests
If a test method requires that a specimen be operational, then the specimen shall be connected to suitable
supply and monitoring equipment with characteristics as required by the manufacturer's data. Unless
otherwise specified in the test method, the supply parameters applied to the specimen shall be set within the
manufacturer's specified range(s) and shall remain substantially constant throughout the tests. The value
chosen for each parameter shall normally be the nominal value or the mean of the specified range.
Where an a.s.d. has multiple sensitivity settings, the sensitivity of the specimen during all tests in Table 3 (with
the exception of the fire sensitivity test in 5.15) shall be set at the highest sensitivity setting used during the
fire sensitivity test(s).
NOTE It is not intended that the environmental tests be conducted at all possible sensitivity settings, only at the
highest used during the fire sensitivity test. This is particularly relevant where multiple classes and/or multiple
configurations are submitted.
8 © ISO 2010 – All rights reserved

To allow a check of the flow monitoring function as required before, during and/or after environmental tests,
the sampling device may be simulated by a simpler sampling device [e.g. stub pipe with appropriate orifice(s)]
to provide a typical airflow through the detector.
During the dry heat, damp heat and cold tests, a sufficient length of pipe shall be installed in the chamber to
allow the temperature of the test aerosol entering the specimen to stabilize at the test temperature.
The details of the supply and monitoring equipment and the alarm criteria used shall be given in the test
report; see Clause 6.
5.1.3 Mounting arrangements
When necessary, the specimen shall be mounted by its normal means of attachment in accordance with the
manufacturer's instructions. If these instructions describe more than one method of mounting, then the
method considered as the most unfavourable shall be chosen for each test.
5.1.4 Tolerances
Unless otherwise specified, the tolerances for the environmental test parameters shall be as given in the basic
reference standards for the test (i.e. the relevant parts of IEC 60068-2).
If a specific tolerance or deviation limit is not specified in a requirement or test procedure, then a deviation
limit of ± 5 % shall be applied.
5.1.5 Measurement of response threshold value
5.1.5.1 General
There are a number of different a.s.d. operating principles, which have different ranges of sensitivity.
Accordingly, various methods can be used to measure the r.t.v. The object of any method chosen shall be to
determine a measure of the aerosol concentration that, when passing through the detector, just causes the
release of an alarm. This can generally be achieved by introducing smoke or an aerosol into the sampled air
stream so that the detector is subjected to a slowly increasing concentration, and recording the concentration
at the moment when an alarm is released. The r.t.v. is used only as a relative measurement; therefore,
various parameters to measure the aerosol concentration may be used, providing that the chosen parameter
is essentially proportional to the particle-number concentration (i.e. a linear relationship) for the particular test
aerosol. Further information is provided in Annex A.
5.1.5.2 Typical r.t.v. measurement procedure
Connect the specimen to measuring apparatus as recommended in Annex A. Control the airflow through the
detector at a typical rate within the manufacturer's specification.
Connect the specimen to the supply and monitoring equipment in accordance with 5.1.2 and allow it to stabilize
for at least 15 min unless otherwise specified by the manufacturer.
Before commencing each measurement, purge the measuring apparatus and specimen sufficiently to ensure
that the result is not affected by the previous measurements.
Increase the aerosol concentration at an appropriate rate, depending upon the sensitivity of the specimen.
The rate of increase in aerosol density shall be similar for all measurements on a particular a.s.d. type. It is
recommended that the alarm signal be released at between 2 min and 10 min after the start of the test.
NOTE Preliminary testing can be necessary to determine the appropriate rate for a particular detector type.
The r.t.v. N shall be taken as the aerosol concentration at the moment when the specimen releases an alarm
signal. The particular measuring unit for the aerosol concentration depends on the measuring apparatus used.
5.1.6 Test of the airflow monitoring facility
In accordance with the requirements in 4.10, the airflow monitoring facility shall be tested as follows.
a) Where the volumetric flow is not maintained at a constant, verify the increase and decrease in flow as
follows.
1) Determine the normal volumetric airflow, F , expressed in litres per minute, from the sampling
n
configuration used for the fire tests using suitable instrumentation.
2) For testing the airflow monitoring, set the test flow rate, F , at the specimen to F ± 10 %. If the
t n
specimen has a memorized normal flow, enter F into the memory in accordance with the normal
t
operating instructions. This shall be done only once at the start of each environmental test and shall
not be done during or after conditioning.
3) For decreased flow, decrease the volumetric airflow from F by 20 % (F − 20 %).
t t
4) For increased flow, increase the volumetric airflow from F by 20 % (F + 20 %).
t t
An example of a possible practical arrangement to achieve this test is given in Annex K.
b) Where the tests of a) cannot be applied (e.g. where the volumetric flow is maintained at a constant), verify
the flow monitoring facility by the loss of a maximum of 50 % of the sampling points by disabling the
furthest sampling points from the sensing element on the worst-case sampling device used in the fire
sensitivity test(s). Test for loss of the points separately as follows.
1) Disable (i.e. close or block off) a total of 50 % of the sampling points furthest from the sensing
element.
2) Break the sampling device such that the same points are disabled by the breakage.
5.1.7 Provision for tests
Eight specimen a.s.d. shall be provided to conduct the tests in the test schedule (see 5.1.8), together with
sufficient sampling pipes and fittings to set up the various sampling device configuration required by the tests.
The specimens submitted shall be representative of the manufacturer's normal production with regard to their
construction and calibration.
This implies that the mean r.t.v. of the eight specimens, found in the reproducibility test, should also represent
the production mean, and that the limits specified in the reproducibility test should also be applicable to the
manufacturer's production.
5.1.8 Test schedule
The specimens shall be tested according to the test schedule in Table 3. The specimens shall be numbered
arbitrarily, with the exception of specimen No. 8.
10 © ISO 2010 – All rights reserved

Table 3 — Test schedule
a
Test Subclause
Specimen No.
Repeatability 5.2 1
b
Reproducibility 5.3 1 to 8
Variation in supply parameters 5.4 1
Dry heat (operational) 5.5 1
Cold (operational) 5.6 1
Damp heat, steady state (operational) 5.7 1
Damp heat, steady state (endurance) 5.8 2
SO corrosion (endurance) 5.9 3
Shock (operational) 5.10 4
Impact (operational) 5.11 4
Vibration, sinusoidal (operational) 5.12 5
Vibration, sinusoidal (endurance) 5.13 5
Electromagnetic compatibility (EMC) immunity tests 5.14 6 and 7
Fire sensitivity 5.15 8
a
The schedule shows the specimen numbers recommended for each test. Other arrangements may be used to improve the
efficiency or cost of testing, or to reduce the number of specimens damaged by the testing. However, the reproducibility of the sensitivity
of at least eight smoke-sensitive parts shall be measured in the reproducibility test. If fewer specimens are being used for the rest of the
tests, then it is necessary to consider the possible damaging effects of subjecting a specimen to a number of tests, especially
endurance tests.
b
The least sensitive specimen shall be designated specimen No. 8 and used in the fire sensitivity tests.

5.2 Repeatability
5.2.1 Object
The object of this test is to show that the detector has stable behaviour with respect to its sensitivity, even
after a number of alarm conditions.
5.2.2 Test procedure
Measure the r.t.v. of the specimen six times in accordance with 5.1.5.
Designate the maximum r.t.v. as N and the minimum as N .
max min
5.2.3 Requirements
The ratio N : N shall not be greater than 1,6.
max min
5.3 Reproducibility
5.3.1 Object
The object of this test is to show that the sensitivity of the detector does not vary unduly from specimen to
specimen.
5.3.2 Test procedure
Test the function of the airflow monitoring facility on each specimen, in accordance with 5.1.6.
Measure the r.t.v. of each of the test specimens in accordance with 5.1.5.
Calculate the mean r.t.v., N .
Designate the maximum r.t.v. as N and the minimum as N .
max min
5.3.3 Requirements
The correct fault signals, in accordance with 4.10, shall be given during the airflow monitoring facility test.
The ratio N : N shall not be greater than 1,33.
max
The ratio N : N shall not be greater than 1,5.
min
5.4 Variation in supply parameters
5.4.1 Object
The object of this test is to show that within the specified range(s) of the supply parameters (e.g. voltage), the
sensitivity of the specimen is not unduly dependent on these parameters.
This may be demonstrat
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