ISO/TR TECHNICAL REPORT 11925-1 First edition 1999-03-15 Reaction to fire tests lgnitability of building products subjected to direct impingement of flame Part 1: Guidance on ignitability Essais de reaction au feu - Allumabilite des produits de batiment soumis a I'incidencedirectedelaflamme- Partie 1: Lignes directrices sur I'allumabilité Tso Referencenumber ISO/TR 11925-1:1999(E) py IHS under itted without license from IHS Not for Resale ISO/TR 11925-1:1999(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 liaison with isO, also take part in the work. isO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. Technical Reports are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3. The main task of technical committees is to prepare International Standards, but in exceptional circumstances, a technical committee may propose the publication of a Technical Report of one of the following types: repeated efforts; type 2, when the subject is still under technical development or where for any other reason there is the future but not immediate possibility of an agreement on an International Standard; type 3, when a technical committee has collected data of a different kind from that which is normally published as an International Standard ("state of the art", for example). Technical Reports of types 1 and 2 are subject to review within three years of publication, to decide whether they can be transformed into International Standards. Technical Reports of type 3 do not necessarily have to be reviewed until the data they provide are considered to be no longer valid or useful. ISO/TR 11925-1, which is a Technical Report of type 3, was prepared by Technical Committee ISO/TC 92, Fire safety, Subcommittee SC 1, Reaction to fire. ISO/TR 11925 consists of the following parts, under the general title Reaction to fire tests - Ignitability of building productssubjectedtodirectimpingementofflame: Part 1: Guidance on ignitability Part 2: Single flame source test Part 3: Multi-source test @ISO1999 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic nternational Organizationfor Standardizatior Case postale 56 . CH-1211 Geneve 20 · Switzerland Internet [email protected] Printed in Switzerland @ ISO ISO/TR 11925-1:1999(E) Introduction lanitabilityofmaterialsisofbasicimportancewhenfirehazardisanalysedbecauseoftworeasons:First,atthe initiation of a fire some object or local area is ignited, and second, during the fire growth period ignitability is an essential factor in fire spread to the other parts of a room or compartment. In buildings the structural, lining and furnishing materials are solids, which require external heating to achieve flaming combustion. The ignition condition can be characterized by the minimum surface temperature at which the flowofvolatilesissufficientforsustainedflaming.However,thedifferenceinthesetemperaturesbetweenmaterials is not large. Hence it is usually more important to take into account the time of exposure and the thermal properties of the material when assessing risk of ignition. When a material is exposed to an external heat flux (radiative, convective, conductive or a combination), its surface temperature starts to rise. The temperature inside the solid also increases with time, but at a slower rate. Provided the net flux into the material is sufficiently high, eventually the surface temperature reaches a level at which layer. Under certain conditions this mixture exceeds the lower flammability limit and ignites. The initiation of flamin