CEN/TS 15912:2012

SLOVENSKI STANDARD
01-september-2012
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Durability of reaction to fire performances - Classes of fire retardant treated wood-based
product in interior and exterior end use applications
Dauerhaftigkeit des Verhaltens bei Brandeinwirkung - Klassen von mit
Feuerschutzmitteln behandelten Holzprodukten für Anwendungen im Innen- und
Außenbereich
Durabilité des performances de réaction au feu - Classes de produits à base de bois
ignifugés pour utilisation finale en intérieur et en extérieur
Ta slovenski standard je istoveten z: CEN/TS 15912:2012
ICS:
71.100.50 .HPLNDOLMH]D]DãþLWROHVD Wood-protecting chemicals
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

TECHNICAL SPECIFICATION
CEN/TS 15912
SPÉCIFICATION TECHNIQUE
TECHNISCHE SPEZIFIKATION
April 2012
ICS 71.100.50
English Version
Durability of reaction to fire performance - Classes of fire-
retardant treated wood-based product in interior and exterior end
use applications
Durabilité des performances de réaction au feu - Dauerhaftigkeit des Verhaltens bei Brandeinwirkung -
Classement des produits à base de bois ignifugés pour Klassen der mit Feuerschutzmitteln behandelten
utilisation finale en intérieur et en extérieur Holzprodukte für Anwendungen im Innen- und
Außenbereich
This Technical Specification (CEN/TS) was approved by CEN on 14 February 2012 for provisional application.

The period of validity of this CEN/TS is limited initially to three years. After two years the members of CEN will be requested to submit their
comments, particularly on the question whether the CEN/TS can be converted into a European Standard.

CEN members are required to announce the existence of this CEN/TS in the same way as for an EN and to make the CEN/TS available
promptly at national level in an appropriate form. It is permissible to keep conflicting national standards in force (in parallel to the CEN/TS)
until the final decision about the possible conversion of the CEN/TS into an EN is reached.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland,
Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2012 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TS 15912:2012: E
worldwide for CEN national Members.

Contents Page
Foreword .4
Introduction .5
1 Scope .6
2 Normative references .6
3 Terms and definitions .6
4 Symbols .7
5 Requirements .7
5.1 Wood-based products and non-fire-retardant coating systems .7
5.2 Reaction to fire performance .8
5.2.1 Initial classification for reaction to fire .8
5.2.2 Reaction to fire performance before and after accelerated or natural weathering .8
5.3 Durability of reaction to fire performance .9
5.3.1 General .9
5.3.2 DRF Class ST .9
5.3.3 DRF Class INT1 .9
5.3.4 DRF Class INT2 .9
5.3.5 DRF Class EXT .9
6 Practices to use the DRF classification system . 11
7 Classification report . 11
Annex A (informative) Test methods . 13
A.1 Hygroscopic properties of fire-retardant treated wood-based products including those
with fire-retardant coatings . 13
A.1.1 General . 13
A.1.2 Field of application . 13
A.1.3 Sampling, sample handling and preparation . 14
A.1.4 Test method . 15
A.2 Accelerated weathering of fire-retardant treated wood for fire testing . 17
A.2.1 General . 17
A.2.2 Field of application . 18
A.2.3 Sampling, sample handling and preparation . 18
A.2.4 Test method . 19
A.3 Building materials and components in the vertical position: Exposure to accelerated
climate strains . 21
A.3.1 General . 21
A.3.2 Field of application . 21
A.3.3 Sampling . 21
A.3.4 Test method . 22
Annex B (informative) Example of classification report . 26
B.1 Classification report: Durability classes of reaction to fire performance of fire-retardant
wood-based products in interior and exterior end use applications according to CEN/TS
15912 . 26
B.1.1 Product . 26
B.1.2 Product specification . 26
B.1.3 Requirements . 27
B.1.4 Evaluation documents . 27
B.1.5 Durability of reaction to fire performance (DRF) Class . 28
B.1.6 Applicability of DRF Class . 28
B.1.7 Service life . 29
Bibliography . 30

Foreword
This document (CEN/TS 15912:2012) has been prepared by Technical Committee CEN/TC 175 “Round and
sawn timber”, the secretariat of which is held by AFNOR.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
According to the CEN/CENELEC Internal Regulations, the national standards organisations of the following
countries are bound to announce this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland, Turkey and the United Kingdom.

Introduction
Fire-retardant treatments may considerably improve the reaction to fire properties of wood and wood-based
products and these may result in wood having the highest fire-resisting characteristics achievable with any
combustible product. However, the reaction to fire performance may be reduced by exposure to wet and/or
humid conditions [1] and the ability of treatments to continue to perform even when exposed to these
conditions needs to be demonstrated.
Two aspects of fire durability of the fire-retardant treatment of wood-based products need to be considered.
One is the risk for high moisture content and migration of the fire-retardant chemicals within the wood product
and salt crystallisation on the product surface. These hygroscopic properties of the treated wood-based
product can be evaluated by exposure to high relative humidity.
The other aspect is the risk for decreased fire performance due to loss of the fire-retardant chemicals by
leaching in exterior applications, e.g. facade claddings. Maintained fire performance after weathering needs to
be verified.
The Technical Specification is based on a Nordtest standard [15] and on experience from North America [7]
[12].
1 Scope
This European Technical Specification describes the characteristics which fire-retardant treated wood
products should exhibit so that their fire-retardant properties persist undiminished throughout the desired
service life in the anticipated conditions of use.
The Technical Specification prescribes the classification requirements for the durability of the reaction to fire
performance of fire-retardant treated wood-based products to be used in interior and exterior end use
conditions. The products initially need to meet required reaction to fire classification. For interior and exterior
use, limited hygroscopicity needs to be verified. In addition, products for exterior use needs to meet the
minimum durability of reaction to fire performance requirements specific to the end use.
The requirements are applicable for fire-retardant treated (applied by penetrating and superficial processes or
with film forming or intumescent fire-retardant coatings) solid wood and wood-based products and wood-
based products in which the fire-retardant is incorporated during manufacture. The fire-retardant treated
products may be coated with an ordinary paint.
Mechanical properties and biological durability of fire-retardant treated wood products are not covered by this
European Technical Specification.
Paints, coatings and varnishes intended to improve the reaction to fire performance of a construction product
when incorporated in the works, i.e. a building, are covered by ETAG 028 [19].
This Technical Specification may be used as a basis for an approval system.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
EN 927-3, Paints and varnishes  Coating materials and coating systems for exterior wood  Part 3: Natural
weathering test
EN 13238, Reaction to fire tests for building products  Conditioning procedures and general rules for
selection of substrates
EN 13823, Reaction to fire tests for building products  Building products excluding floorings exposed to the
thermal attack by a single burning item
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
durability of reaction to fire performance
DRF
four classes for the Durability of Reaction to Fire performance are defined:
 DRF Class ST for short term use (e.g. less than one year); no durability performance shall be verified;
 DRF Class INT1 for permanent use in interior applications, service class 1 (e.g. wall and ceiling
products);
 DRF Class INT2 for permanent use in interior applications and certain protected exterior applications,
service class 2 (e.g. wall and ceiling products);
 DRF Class EXT for permanent use in exterior applications, service class 3 (e.g. facade claddings,
exterior conditions)
3.2
service classes
3.2.1
dry condition
moisture content in the materials corresponding to a temperature of 20 ºC and the relative humidity of the
surrounding air only exceeding 65 % for a few weeks per year
Note 1 to entry: In Eurocode EN 1995-1-1 as Service class 1.
3.2.2
humid condition
moisture content in the material corresponding to a temperature of 20 °C and a relative humidity of the
surrounding air only exceeding 85 % for a few weeks per year
Note 1 to entry: In EN 1995-1-1 defined as Service class 2.
3.3
ordinary paint
non-fire retardant paint
4 Symbols
The symbols for DRF Classes ST, INT1, INT2 and EXT are the followings:

Figure 1 — Proposed symbols for classes
5 Requirements
5.1 Wood-based products and non-fire-retardant coating systems
The treatment manufacturing process and application rate declared by the producer shall be declared by the
manufacturer of the final product. Remaining fire-retardant chemicals in terms of kg/m of the final wood-
based product, or in terms of kg/m for surface treated products, shall be specified. Values shall be given for
products conditioned at (50 ± 5) % relative humidity at (23 ± 2) °C (as for fire testing).
For products in DRF Classes INT and EXT the following procedures shall be provided by the manufacturers:
 type of maintenance;
 interval of maintenance;
 time until to the first maintenance/recoating (if relevant);
 coating system to be used initially and at maintenance (if relevant).
Verification of DRF Class EXT obtained without a coating system (with an ordinary paint) is valid also for the
same product coated, provided that the coating does not reduce the reaction to fire performance.
NOTE The maintained fire performance of a coated product (with an ordinary paint) may be verified by fire testing
e.g. in the cone calorimeter.
Verification of DRF Class EXT is valid for thicker wood-based products than verified, but not for thinner.
5.2 Reaction to fire performance
5.2.1 Initial classification for reaction to fire
Classification testing for reaction to fire performance shall be performed. The products have to fulfil a specified
fire performance according to a recognised reaction to fire standard. Relevant systems are, for instance, the
European reaction to fire classification system according to EN 13501-1 and for products which are not used
in construction, the IMO Code FTP [2].
5.2.2 Reaction to fire performance before and after accelerated or natural weathering
5.2.2.1 General
Reaction to fire performance before and after weather exposure shall be performed according to 5.2.2.2.
The weather exposure shall be performed according to an accelerated procedure, see A.2, or a similar
accelerated test procedure, e.g. 5 months exposure in A.3, or natural weathering according to EN 927-3, or at
relevant and specified outdoor conditions for at least 5 years.
NOTE 1 For the accelerated weathering, it is essential that the exposed samples are large enough to be fire tested.
Thus the minimum width is 100 mm (minimum according to ISO 5660-1).
NOTE 2 For the accelerated weathering, it is also essential that the exposed samples are large enough to fulfil the
cutting requirements in 5.2.2.2.2 and A.2.
NOTE 3 For the natural weathering, exposure at 45° slope is recommended.
Natural weathering at relevant conditions for the specific end use is most desirable, but such data are usually
not available. It is recommended that a set of the products going through an accelerated weathering
procedure is also exposed to natural weathering.
Additional variations of the product, e g additional coating systems (with ordinary paints), could preferably be
evaluated at the same time. Examples of weathering studies are given in [4] [5].
5.2.2.2 Testing for reaction to fire performance
5.2.2.2.1 Generality
The reaction to fire performance after weathering shall be tested according to one of the following two
procedures:
5.2.2.2.2 Classification testing
The same test methods as for the initial classification according to 5.2.1 may be used. For testing according to
EN 13823, only one replicate may be used for the fire testing after weathering.
5.2.2.2.3 Small scale testing
Alternatively, fire testing may be performed according to ISO 5660-1 (cone calorimeter) at a heat flux
50 kW/m for at least 1 200 s. Conditioning for ISO 5660-1 tests is carried out in the same way as according to
EN 13238.
If this alternative is chosen, testing of the product before weathering is also needed for comparison of the fire
performance before and after weathering.
NOTE 1 This alternative is justified by correlation studies with methods for classification test methods, e.g. [16] [17]
[18].
The preparation of small test specimens of fire-retardant treated wood and wood based products are very
important for the test results obtained, since the amount of fire-retardant chemicals may vary between small
samples. This is especially important for impregnated solid wood products. Such specimens shall therefore be
cut in order to represent the fire properties of the full wood plank. A suitable procedure is specified in [3].
NOTE 2 The following conclusions on sampling of wood panelling are given in [3]:
− Specimens should be cut approximately 1 m from the end of the plank;
− Specimens should not have knots in the centre area – knots covered by the frame may be used.
5.3 Durability of reaction to fire performance
5.3.1 General
The following items shall be reported for each DRF class.
5.3.2 DRF Class ST
 Reaction to fire class, initial, according to 5.2.1.
5.3.3 DRF Class INT1
 Reaction to fire class, initial, according to 5.2.1;
 Hygroscopic properties at (70 ± 5) % RH and (25 ± 2) °C according to A.1. The test shall be carried out
with samples uncoated (with an ordinary paint). The equilibrium moisture content shall be < 20 %.
5.3.4 DRF Class INT2
 Reaction to fire class, initial, according to 5.2.1;
 Hygroscopic properties at (90 ± 5) % RH and (27 ± 2) °C according to A.1. The test shall be carried out
with samples uncoated (with an ordinary paint). The equilibrium moisture content shall be < 28 %.
5.3.5 DRF Class EXT
a) Reaction to fire class, initial, according to 5.2.1:
1) Initial fire class;
2) Maintained fire performance after weathering according to 5.2.2.1 and Table 1;
b) Hygroscopic properties at (90 ± 5) % RH and (27 ± 2) °C according to A.1. The test shall be carried out
with samples uncoated (with an ordinary paint). Equilibrium moisture content shall be < 28 %.
NOTE 1 Products in DRF Class EXT meet the criteria DRF Class INT1 and INT2, but not vice versa.
NOTE 2 Background information on cirtieria for reaction to fire performance is available in [16] [17] [18].
Table 1 — Requirements for DRF Classes of fire-retardant wood-based products in interior and
exterior end use applications
DRF class Existing fire Additional performance requirements at different end
a
requirements use of fire-retardant wood-based products
b
Intended Reaction to fire Hygroscopic properties  Reaction to fire
use class, initial performance after
weather exposure
ST Short term Relevant fire class - -
INT1 Interior dry Relevant fire class - Moisture content < 20 % -
applications - No exudation of liquid
- Minimum visible salt with no
increase at surface
INT2 Interior Relevant fire class - Moisture content < 28 % -
humid - No exudation of liquid
applications - Minimum visible salt with no
increase at surface
Maintained reaction to fire
e c, d
EXT Exterior Relevant fire class - Moisture content < 28 % performance  after
applications - No exudation of liquid - Accelerated weathering
- Minimum visible salt with no or
increase at surface  - Natural weathering or
- Other referenced and
recognised weathering
method
Application of specified
maintenance may be
included.
a
To be fulfilled using product produced in the same way using the same manufacturing process and having a similar retention
level as for the reaction to fire performance.
b
For INT1 at (70 ± 5) % RH and (25 ± 2) °C and for INT2 at ( 90 ± 5) % RH and (27 ± 2) °C according to A.1. Classes INT1,
INT2 and EXT are only applicable for product application rates less than or equal to the highest level tested. Wood products
treated to higher application rates will be assumed to be Class ST.
c
Criteria for fire testing according to 5.2.2.2.2 after weather exposure:
Class B products: RHR ≤ 150 kW/m during 600s after ignition and THR increase < 20 % compared to testing before the
30s ave 600s
weather exposure.
Class C products: RHR ≤ 220 kW/m during 600s after ignition and THR increase < 20 % compared to testing before the
30s ave 600s
weather exposure.
For the other methods according to 5.2.2.2.1, the relevant classification criteria shall be used. The same classification level shall
be reached.
d
For DRF Class EXT, the Durability of Reaction to Fire performance classification is only valid for the type of coating system
(with an ordinary paint) to be verified.
e
Verification of DRF Class EXT obtained without a coating system (with an ordinary paint) is valid also for the same product
coated, provided that the coating does not reduce the reaction to fire performance.

6 Practices to use the DRF classification system
 DRF INT1 and INT2 classifications apply for the life time of the wood product provided the product is only
used in the intended service class;
 DRF Class EXT is complex with a number of factors to be considered. The manufacturers should be
consulted regarding service life;
 Manufacturers of fire-retardant wood-based products with DRF classification shall use a third party
production control system according to Attestation of Conformity system 1;
 Systems in the relevant product standards for CE-marking may preferably be used, since they include
high attestation of conformity levels for fire-retardant treated wood products;
 Documentation shall include instructions on maintenance frequency and methods according to 5.1;
 Products approved with a DRF class ST, INT1, INT2 or EXT, should be individually marked with DRF
Class symbols (see below) unless for aesthetic reasons this is not practical and with DRF Class,
producer’s name, name of fire-retardant product or trade name on the package label;
 Year of initial testing in the symbol, or beside, may be used, see Figure 2.

Figure 2 — Proposed labels to be used for DRF classes ST, INT1, INT2 and EXT with year of initial
testing
7 Classification report
Classification report according to this document shall be issued by accredited institutes and approval bodies.
The classification report shall include the following items:
 Name and address of the national institute or approval body;
 Name and address of the organisation or person stating the classification;
 Name and address of the manufacturer or supplier of the product;
 Identification of the wood-based product including type of fire-retardant treatment, retention level and
coating details;
 A general description of the product including density and thickness;
 Initial reaction to fire class obtained according to e.g. EN 13501-1 or IMO Code FTP, incl. details on
mounting and fixing;
 Identification and number of the test reports referred to;
 Accelerated weathering method used for DRF Class EXT;
 Information if any maintenance has to be performed during use;
 Hygroscopicity and weathering tests, including test method employed;
 Performance according to the criteria for the actual DRF class;
 Reference to this Technical Specification and the fire classification standard used.
The format for a classification report is given in Annex B.
Annex A
(informative)
Test methods
A.1 Hygroscopic properties of fire-retardant treated wood-based products including
those with fire-retardant coatings
A.1.1 General
This test method prescribes the procedure for determining the equilibrium moisture content after exposure to
standard high relative humidity conditions of (70 ± 5) % at (25 ± 2)°C or (90 ± 5) % at (27 ± 2)°C, depending
on DRF class. The method is based on NT Build 504 [6], with changes in A.1.3 and an additional humid
climate included for testing. It is a modified and extended version of ASTM D 3201-94 (with the same title) [7].
The extension aims at more repeatable and reproducible results by requiring conditioning to equilibrium
moisture content (instead of a specified time, one week, without specifying the sample size or air velocities in
the climate chamber in the ASTM version).
In this European Technical Specification, some further modifications are included, mainly testing for two
interior cases, dry and humid.
A.1.2 Field of application
 The method is applicable for assessing the hygroscopic properties of fire-retardant treated solid wood and
wood-based products (with the fire-retardant incorporated during the manufacturing of the wood-based
product). It is also applicable for wood products with fire-retardant coatings, including film-forming, non-
film-forming and intumescent coatings. The hygroscopic properties of wood and wood-based products
treated with fire-retardant chemicals may be greater than for untreated products. This is particularly true
at the higher relative humidity conditions. This higher hygroscopicity may cause staining, decay, poor
paint adhesion, migration and exuding of chemicals and moisture at the high humidities. Corrosion of
metal fasteners may also occur. The results obtained with this Technical Specification are important in
determining if the fire-retardant treated wood or wood-based product has undesirable hygroscopic
properties, i.e. reaches an equilibrium moisture content that exceeds that for untreated wood and the
maximum prescribed level for the applicable DRF Class.
 Two test options are included, one general option and one specific option for end use products.
 The gereral test option for impregnation treatments and fire-retardant coatings is carried out using Scots
pine (Pinus sylvestris) sapwood, since this will give characterised products with a known level of
penetration and retention. Results for Scots pine sapwood at a given retention are assumed to be
applicable to the treated sapwood of other species at the same retention. Where higher retentions are
targeted commercially, for example to achieve different fire classifications, additional hygroscopicity
testing shall be carried out at the applicable retention for that product.
 The specific test option for end use products is carried out using that product. The results are limited to
that product.
 When consideration of hygroscopicity is concerned, it is the treated zone retention not the overall
retention that is of concern. It is important to understand that the overall retention achieved during a
charge is not the same as the treated zone retention. The overall retention of a commercially treated
product is likely to be significantly lower than that of the treated zone retention since the commercial
product is likely to contain untreated areas (e.g. untreated heartwood in the case of impregnation
treatments). The treated zone retention is equal to the charge retention divided by the proportion of the
timber penetrated.
 All fire-retardant treated products are to be tested in an uncoated manner (without an ordinary paint).
Hygroscopicity results apply to coated and uncoated products.
A.1.3 Sampling, sample handling and preparation
A.1.3.1 General procedure
A.1.3.1.1 Generality
This general procedure may be used to generate data applicable to all wood species with the same or lower
3 2
retention level (kg/m or kg/m ).
A.1.3.1.2 Preparation of test specimens
A.1.3.1.2.1 Generality
Specimens shall be selected from Scots pine (Pinus sylvestris) sapwood that is free from knots, visible cracks,
stain, decay, insect damage and other defects. For impregnation treatments, the specimen size shall be
50 mm x 25 mm x 15 mm +/- 10 % with three replicates. For surface treated products, the specimen size shall
be 200 mm x 100 mm x 2 mm +/- 10 % with three replicates.
A.1.3.1.2.2 Conditioning of test specimens before impregnation treatment
o o
Place the numbered test specimens in an oven maintained at 103 C +/- 2 C and leave them there for a
minimum of 18 hours. Cool to room temperature in a dessicator and weigh to the nearest 0,01 g to determine
the initial dry mass. Replace the test specimens in a dessicator and store them there in order to keep them dry
until treatment.
A.1.3.1.2.3 Impregnation treatments - Impregnation of test specimens
Place the specimens in a treatment vessel and ballast to prevent them from floating when the liquid is
admitted. Place the treatment vessel in a vacuum vessel and reduce the pressure to (0,7 +/-0,1) kPa. Maintain
this vacuum for 15 min. After this period and whilst maintaining the vacuum, allow the fluid to enter the
treatment vessel. Add sufficient fluid to ensure that the samples are submerged throughout the remainder of
the impregnation process. Next, admit air to bring the vacuum vessel back to atmospheric pressure. Remove
the treatment vessel with its submerged specimens from the vacuum vessel and leave for 2 h. After
impregnation, remove the specimens one by one, remove the excess liquid by light blotting with absorbent
paper and immediately weigh to the nearest 0,01 g to ascertain the mass after treatment. Alternatively,
suitable equipment for vacuum/ high pressure impregnation of the blocks may be used.
A.1.3.1.2.4 Surface treated test specimens and fire-retardant coatings
Apply the target loading to all faces. Record the final mass after each coat to ascertain the total application
rate.
A.1.3.1.2.5 Drying of test specimens
Air dry the specimens at ambient temperature for a minimum of two weeks. If the nature of the fire-retardant is
such that additional or alternative procedures are required (e.g. a curing stage), dry as necessary in
accordance with the manufacturer’s instructions. Details of the drying procedure used shall be included in the
test report. Transfer the samples to the conditioning chamber.
A.1.3.1.2.6 Results
For impregnation treatments and wood-based products where the fire-retardant is incorporated during
production (engineered wood products), calculate the mass of the fire-retardant retained per unit volume of
wood in kilograms per cubic meter, for each test specimen.
For surface treated and fire-retardant coated products, calculate the mass of the fire-retardant retained per
unit area of wood in kilograms per square meter, for each test specimen. If more than one coating is used
(e.g. base coat and top coat), calculate separately the uptake for each coating.
The applied retention shall be at least the same as required for fire classification.
A.1.3.2 Procedure for end use products
A.1.3.2.1 Generality
This procedure may be used to generate data applicable to the wood product tested only.
A.1.3.2.2 Preparation of test specimens
Wood-based products where the fire-retardant is incorporated during production (engineered wood products)
should be representative of the lot. The specimen size shall be 200 x 100 x commercial thickness (mm) with
three replicates. For surface treated products and fire-retardant coatings, the specimen size shall be 200 x
100 x minimum commercial thickness (mm) with three replicates.
The applied retention shall be at least the same as required for fire classification.
A.1.3.3 Untreated specimen
Untreated Scots pine sapwood specimens of the same size shall be exposed to the pre-conditioning, high-
humidity exposure and drying along with the treated specimens.
A.1.4 Test method
A.1.4.1 Principle
The test is based on gravimetric measurements.
A.1.4.2 Equipment
 Conditioning rooms or chambers capable of maintaining the climates (90 ± 5) % RH at (27 ± 2)°C,
(70 ± 5) % RH at (25 ± 2)°C and (50 ± 3) % RH at (23 ± 2)°C;
 Oven, air-circulated and vented, capable of maintaining a temperature of (103 ± 2)°C;
 A balance that will weigh a specimen within an accuracy of ± 0,1 %;
 Trays or bowls for collecting exuded liquid from each specimen at high moisture exposure; see A.1.4.5.1.
A.1.4.3 Testing environment
See A.1.4.2, A.1.4.4 and A.1.4.5.1.
A.1.4.4 Pre-conditioning of specimens
The specimens shall be conditioned at (50 ± 3) % RH at (23 ± 2)°C until constant mass prior to the high-
humidity exposure and at least for 7 days.
A.1.4.5 Test procedure and data processing
A.1.4.5.1 Test procedure
a) Weigh each specimen to an accuracy of ± 0,1 %;
b) Expose all specimens under constant humidity conditions of (90 ± 5) % at (27 ± 2)°C or (70 ± 5) % RH at
(25 ± 2)°C until constant mass is obtained. Specimens shall be suitably stacked so that all surfaces are
exposed.
c) If it is likely that the specimen might exude moisture or chemicals or both under the exposure conditions,
provisions should be made to collect any drippings and include the weight with the specimen weight. One
tray or bowl per specimen shall be used. Report if exudation occurs.
d) Weigh each specimen immediately to an accuracy of ± 0,1 %, one at a time, as they are removed from the
conditioning chamber. Repeat the weighing at regular intervals until constant mass is achieved. Constant
weight can be assumed when two consecutive readings at intervals of at least 24 h agree within 0,1 %.
The specimens should be returned to the conditioning chamber immediately after weighing. Observe and
record the general appearance of the specimens, e.g. salt stains on the surface.
e) Dry each specimen in an oven at 103 ± 2°C until approximately constant weight is attained, and reweigh.
Constant weight can be assumed when two consecutive readings taken 2 h apart agree within 0,1 %.
Avoid drying for periods longer than necessary to achieve constant weight, since thermal decomposition
of chemical or wood might occur reflecting a higher than actual moisture content.
A.1.4.5.2 Data processing
a) Calculate the moisture content of each sample prior to high-humidity exposure as follows:
Moisture content, % = [(A – B) / B] × 100
where A = weight prior to high-humidity exposure
B = oven dry treated weight.
b) Calculate the equilibrium moisture content of each sample after high-humidity exposure as follows:
Moisture content, % = [(C – B) / B] × 100
where C = weight after high-humidity exposure (including any liquid exuded from the fire-retardant treated
wood)
B = oven dry treated weight.
A.1.4.6 Applicability
The results will be useful in determining exposure limitations in service for specific treated products.
A.1.4.7 Untreated reference
Untreated control specimen shall always be used to provide information on the high-humidity conditions used.
A.1.4.8 Test report
Report the following information:
a) Complete identification of the fire-retardant product: solid timber, engineered wood product, impregnation
treatment, fire-retardant coating details, solution concentration applied retention rate/s, number of coats,
nature of coats;
b) Description of sampling procedures, number and dimensions of test specimens;
c) Procedure used for sampling, sample handling and preparation (general procedure or Procedure for end
use products);
d) General description of humidity chamber and controls used for the test;
e) The moisture content for untreated specimens exposed simultaneously with the treated specimens;
f) The moisture content for the treated specimens, both before and after high-humidity exposure, shall be
reported; the change in the average moisture content after high-humidity exposure compared to the
moisture content of untreated specimens (c) shall also be reported;
g) Any changes in the appearance of the specimen during exposure, chemical exudation, salt stains,
discoloration of coating;
h) Name and address of the testing laboratory, including identification number of the test report;
i) Name and address of the organisation or person ordering the test;
j) Name and address of the manufacturer or supplier of the tested object;
k) Date of supply of tested objects and duration of test period.
A.1.4.9 Acceptance or rejection of the result
Rules for acceptance, see Table 1 in 5.3.5, based on maximum moisture content and appearance of
specimen.
A.2 Accelerated weathering of fire-retardant treated wood for fire testing
A.2.1 General
The durability of a fire-retardant treatment of wood under exposure to accelerated weathering is covered by
this Technical Specification.
Two alternative methods are described, A and B, both suitable for application to a test specimen prior to
subjecting that specimen to an appropriate fire test. These methods are applicable to treated wood products
or assemblies thereof. The test specimens will be in the form of, or suitable for fabrication into, fire test
specimens.
This method is based on Nordtest Method NT Fire 053 [11] and ASTM D 2898-94 [12] (with the same title)
and slightly extended. Pre-conditioning and weighing of specimen are added to increase the output
information from the test. Rules for edge seal of small specimens are also added.
A.2.2 Field of application
 This European Technical Specification provides a choice between two methods, A and B, of exposing
fire-retardant treated (fire-retardant treated) wood products or assemblies to controlled accelerated
weathering. The exposure simulates effects of leaching, drying, temperature and, in method B, also
ultraviolet light;
 A research study [8] showed that the two exposure methods, A and B, were equivalent in leaching effect
as demonstrated by the flame-spread results obtained on specimens exposed by either method when fire
tested by ASTM E 84 [9], the 25-foot tunnel test, and ASTM E 286 [10], the 8-foot tunnel test (now
withdrawn);
 The weathering results for the species and thickness combination tested apply to other species and
thickness combinations;
 Products should be tested at the application rate used in practice;
 Products may be tested with an ordinary coating, e g a primer and top coat for exterior applications, but
the results will then be valid only for products with this coating.
A.2.3 Sampling, sample handling and preparation
The test specimen shall include all those essential parts of the corresponding fire test specimen that may be
subjected to weather exposure in normal use.
Products may be tested with an ordinary coating, e.g. a primer for exterior applications, but the results will
then be valid only for products with this coating.
Products to be tested should be treated to an application rate at least equal that given in a fire classification
report (or supporting document e.g. fire test report). If this is not well documented (documentation could be for
example by mass uptake of the test pieces and a comparison with retention data in fire classification reports),
an initial fire test is required, see 5.2.1.
 The specimen size shall be the same as for the subsequent fire testing or preferably larger. A minimum
size along the grain shall be 500 mm; recommended 800 mm for accelerated weathering;
 The edges perpendicular to grain shall be sealed in order to avoid excessive leaching due to small
sample size. A suitable seal consists of a thin coat of alkyds primer and a thick top coat of silicon sealer;
 If the fire testing i
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