oSIST prEN ISO 24966:2025

SLOVENSKI STANDARD
01-julij-2025
Določanje plamenišča - Modificirana metoda plamenišča v neprekinjeno zaprti
posodi (MCCCFP) (ISO/DIS 24966:2025)
Determination of flash point - Modified continuously closed cup flash point (MCCCFP)
method (ISO/DIS 24966:2025)
Flammpunktbestimmung - Modifizierte Methode dauerhaft geschlossener Tiegel
(MCCCFP) (ISO/DIS 24966:2025)
Détermination du point d'éclair - Méthode modifiée du point d'éclair en vase clos en
continu (MCCCFP) (ISO/DIS 24966:2025)
Ta slovenski standard je istoveten z: prEN ISO 24966
ICS:
75.160.20 Tekoča goriva Liquid fuels
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
International
Standard
ISO/DIS 24966
ISO/TC 28
Determination of flash point —
Secretariat: NEN
Modified continuously closed cup
Voting begins on:
flash point (MCCCFP) method
2025-05-16
ICS: 75.100; 75.160.40; 75.160.20
Voting terminates on:
2025-08-08
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
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Reference number
ISO/DIS 24966:2025(en)
DRAFT
ISO/DIS 24966:2025(en)
International
Standard
ISO/DIS 24966
ISO/TC 28
Determination of flash point —
Secretariat: NEN
Modified continuously closed cup
Voting begins on:
flash point (MCCCFP) method
ICS: 75.100; 75.160.40; 75.160.20
Voting terminates on:
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2025
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
STANDARDS MAY ON OCCASION HAVE TO
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BE CONSIDERED IN THE LIGHT OF THEIR
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Published in Switzerland Reference number
ISO/DIS 24966:2025(en)
ii
ISO/DIS 24966:2025(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Chemicals and materials . 2
6 Apparatus . 2
7 Apparatus preparation . 2
7.1 General .2
7.2 Location of the apparatus .2
7.3 Cleaning the test chamber and sample cup .2
7.4 Apparatus assembly .3
7.5 Apparatus verification .3
8 Sampling . 3
9 Sample handling . 4
9.1 Sub-sampling .4
9.2 Sample containing undissolved water.4
9.3 Samples that are liquid at ambient temperature .4
9.4 Samples that are very viscous, semi-solid or solid at ambient temperature.4
10 Procedure . 4
10.1 General preparations .4
10.1.1 Settings .4
10.1.2 Dry cup heating procedure .5
10.1.3 Selection of initial temperature .5
10.2 Flash point test procedure .5
11 Calculation . 6
11.1 Conversion of barometric pressure reading .6
11.2 Correction of detected flash point to flash point at standard atmospheric pressure .6
12 Expression of results . 7
13 Precision . 7
13.1 General .7
13.2 Repeatability, r .7
13.3 Reproducibility, R .7
14 Test report . 7
Annex A (normative) Apparatus verification using reference materials . 8
Annex B (normative) Flash point apparatus .11
Bibliography .15

iii
ISO/DIS 24966:2025(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/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 Technical Committee ISO/TC 28, Petroleum and related products, fuels and
lubricants from natural or synthetic sources.
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/DIS 24966:2025(en)
Introduction
Flash point values are used in shipping, storage, handling, and safety regulations, as a classification
property to define “flammable” and “combustible” materials. Precise definition of the classes is given in each
particular regulation.
A flash point value can indicate the presence of highly volatile material(s) in a relatively non-volatile or
non-flammable material and flash point testing can be a preliminary step to other investigations into the
composition of unknown materials.
It is not appropriate for flash point determinations to be carried out on potentially unstable, decomposable,
or explosive materials, unless it has been previously established that heating the specified quantity of such
materials in contact with the metallic components of the flash point apparatus, within the temperature
range required for the method, does not induce decomposition, explosion or other adverse effects.
Flash point values are not a constant physical-chemical property of materials tested. They are a function of
the apparatus design, the condition of the apparatus used, and the operational procedure carried out. Flash
point can therefore be defined only in terms of a standard test method, and no general valid correlation can
be guaranteed between results obtained by different test methods or with test apparatus different from
that specified.
[8]
ISO/TR 29662 gives useful advice in carrying out flash point tests and interpreting their results.

v
DRAFT International Standard ISO/DIS 24966:2025(en)
Determination of flash point — Modified continuously closed
cup flash point (MCCCFP) method
WARNING — The use of this document can involve hazardous materials, operations and equipment.
This document does not purport to address all of the safety problems associated with its use. It is
the responsibility of users of this document to take appropriate measures to ensure the safety and
health of personnel prior to the application of the standard, and to determine the applicability of any
other restrictions for this purpose.
1 Scope
This document describes a test method for the determination of the continuously closed cup flash point
of chemicals, lube oils, fuels including aviation turbine fuel, diesel fuel, diesel/biodiesel blends and related
products. The precision of this method has been determined over the range of 24,5 °C to 229,5 °C.
NOTE Apparatus can determine the flash point at higher or lower temperatures than the precision range, however
the precision has not been determined.
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 3170, Petroleum Liquids — Manual sampling
ISO 3171, Petroleum liquids — Automatic pipeline sampling
3 Terms and definitions
For the purposes of this document, the following terms and definitions 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/
3.1
flash point
lowest temperature of the test portion, adjusted to account for variations in atmospheric pressure from
101,3 kPa, at which application of an ignition source causes the vapours of the test portion to ignite under
specified conditions of test
Note 1 to entry: For the purpose of this test method, the test portion is deemed to have flashed when the ignited
vapour causes an instantaneous pressure increase of at least 20,0 kPa inside the closed test chamber.
3.2
arc
luminous discharge of electrical current that is formed when a strong current jumps a gap between two
electrodes
ISO/DIS 24966:2025(en)
4 Principle
A 2 ml test portion is introduced into the sample cup which is then raised and pressed onto the lid to form
the continuously closed but unsealed test chamber. The lid is heated at a prescribed, constant rate. For the
flash tests, a high voltage arc of defined energy is discharged inside the test chamber at regular intervals.
After each arc application, the instantaneous pressure increase above the barometric pressure inside the
test chamber is monitored. When the pressure increase is equal or exceeds 20,0 kPa, the temperature at
that point is recorded as the detected flash point. The detected flash point temperature is corrected for
the variation in ambient pressure from a standard pressure of 101,3 kPa. When no flash point is detected,
a defined amount of air dependent on the test portion temperature is introduced into the test chamber to
provide the necessary oxygen for the next flash test.
5 Chemicals and materials
5.1 Cleaning solvent, for removal of traces of sample from the sample cup and lid.
The choice of solvent will depend upon the previous material tested, and the tenacity of the residue. Low
volatility aromatic (benzene free) solvents may be used to remove traces of oil, and mixed solvents such as
toluene-acetone-methanol can be efficacious for the removal of gum-type deposits.
5.2 Reference material (RM), for flash point, certified reference materials (CRM) and/or secondary
working standards (SWS) as described in Annex A.
6 Apparatus
6.1 The apparatus, is described in normative Annex B, and this includes the details of the test chamber
and sample cup together with dimensions. The critical elements are shown in Figure B.1.1 and Figure B.1.2.
6.2 Circulating bath or tap water (optional), may be required for cooling the heat sink of the apparatus
for flash point test temperatures below 5 °C.
6.3 Cooling cup (optional), cup made of plastic material to avoid ice formation during cooling to initial
temperatures equal or less than 0 °C.
6.4 Pipette or syringe, for the introduction of 2,0 ml ± 0,2 ml test portion.
7 Apparatus preparation
7.1 General
Follow the manufacturer’s instructions for the correct set-up, calibration, verification (7.5) and operation of
the apparatus.
7.2 Location of the apparatus
Support the apparatus (6.1) on a level and steady surface in a draught-free position.
7.3 Cleaning the test chamber and sample cup
Clean the sample cup, sample temperature sensor, lid, arc pins and stirring magnet with a tissue or with
an appropriate solvent (5.1) to remove any traces of gum or residue remaining from a previous test. When
solvents are used dry with a stream of clean air to ensure complete removal.

ISO/DIS 24966:2025(en)
7.3.1 Optionally, cleaning arcs can be set to burn off residuals from the arc pins. These cleaning arcs are
automatically initiated before the flash point test is started.
7.4 Apparatus assembly
Examine the sample cup and other parts to ensure that they are free from signs of damage and deposits.
7.5 Apparatus verification
7.5.1 Check the temperature sensors used to monitor the temperature of the test portion and of the
lid against a certified reference thermometer at least once a year. Use only reference thermometers with
calibration/verification traceable to an authorized certification body. If the displayed temperature readings
deviate from the reference thermometer by more than 0,2 °C for the sample sensor and 0,5 °C for the lid
sensor, at either one of the two temperature calibration points, follow the manufacturer's instructions for
corrections.
7.5.2 Check the pressure transducer at least once a year using the atmospheric barometric pressure as
a reference.
If the displayed atmospheric pressure deviates from the atmospheric pressure by more than 0,5 kPa, follow
the manufacturer's instructions for corrections.
Warning — Many aneroid barometers, such as those used at weather stations and airports, are
pre-corrected to give sea level readings. These shall not be used for verification of the pressure
transducer.
7.5.1 Verify the correct amount of air being introduced at least once per year. Follow the manufacturer’s
instructions.
7.5.2 Verify the correct functioning of the apparatus at least once a year by testing a certified reference
material (CRM) (see 5.2 and Annex A). It is recommended that more frequent verification checks are made
using an RM (see 5.2 and Annex A).
7.5.3 The result of a single test obtained for an RM shall be equal to or less than R /√2 from the certified
value of the CRM or from the accepted reference value (ARV) of the SWS, where R is the reproducibility.
7.5.4 The numerical values obtained during the verification check shall not be used to provide a bias
statement, nor shall they be used to make any correction to the flash points subsequently determined using
the apparatus.
If the instrument fails the verification test, it is recommended that the operator follow the manufacturers’
instructions and also check the following and then repeat the verification check:
a) the sample cup is not damaged
b) cleanliness of the lid, sample temperature sensor and arc pins
c) ignition source operates correctly
If there is no obvious non-conformity, conduct a further verification check using a different RM. If the result
conforms to the tolerance requirements, record this fact. If it is still not within the required tolerances,
contact the manufacturer.
8 Sampling
8.1 Unless otherwise specified, obtain representative samples for analysis in accordance with the
procedures given in ISO 3170 or ISO 3171.

ISO/DIS 24966:2025(en)
8.2 Do not store samples for an extended period of time in gas permeable containers, such as
...