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Towards durability classification of preservative treated wood – first attempts using different European standards
2018 - RG/WP 18-20638
EN 350 (2016) gives guidance on methods for determining and classifying the durability of wood and wood-based material against biological wood destroying agents. “Wood-based materials are those derived from trees and include amongst others: untreated wood, heat treated wood, chemically modified wood, glue laminated wood, wood-based panels, wood polymer composites and wood treated with wood preservatives”. Very few data are yet available for assigning durability classes to preservative treated wood on the basis of results from test methods referred to in EN 350 (2016). In this study results from tests according to EN 113 (1996), ENV 807 (2001), and EN 252 (2014) were evaluated, for assigning durability classes of differently preservative treated wood, using different classification schemes. Specimens made from beech (Fagus sylvatica) and Scots pine (Pinus sylvetris) were treated with four different retentions of two wood preservative systems. Results show, that different tests lead to durability classification between 1 (very durable) to 5 (not durable) for same tested combinations. Most treated wood achieved higher durability classes based on test against basidiomycetes (EN 113) compared to tests against soil inhabiting micro-organisms (ENV 807 and EN 252). In summary, it became evident that durability classification of preservative treated wood strongly depends on both, the applied test method and the evaluation scheme used for assigning durability classes.
S Bollmus, A Gellerich, C Brischke, H Militz
Durability classification of preservative treated and modified wood
2019 - IRG/WP 19-20659
EN 350 (2016) allows formally to determine durability classes (DC) for wood products and wood-based materials, which was previously only possible for untreated wood in the form of natural durability. In a first study, the University of Goettingen carried out the durability classification of chemically modified (modified with 1,3-dimethylol-4,5-dihydroxyethyleneurea, DMDHEU) and preservative-treated specimens of various hardwoods and softwoods. The objectives of the work were the determination of mass losses caused by basidiomycetes (CEN/TS 15083-1, 2005) and soft rot fungi (CEN/TS 15083-2, 2005) and to classify durability according to EN 350 (2016). The results showed that a durability classification of chemically modified and preservative treated wood is possible. The tests CEN/TS 15083-1 (basidiomycetes) were carried out with the test fungi C. puteana and T. versicolor and showed that the durability classification is based predominantly on the mass losses caused by C. puteana. However, the distribution of the mass loss values is high, especially for DMDHEU modified collectives. Examinations in accordance with CEN/TS 15083-2 have in many cases led to similar classifications as the tests according to CEN/TS 15083 1. The methodology for evaluating the data proposed in EN 350 (2016) needs to be optimized.
S Bollmus, L Bachle, C Brischke, H Militz
Visual Inspection – How Important is the Influence of the Evaluator?
2013 - IRG/WP 13-20521
Visual inspection is often a crucial means of judging the efficacy and performance of a preservative. It is used in non-destructive testing in long term exposure trials or simply, when the practical use and precision of the human eye is a good means of measure. As for the procedure described in EN 252, the impression of softness due to decay of the wood has also to be considered. Although, a thumb and an eye are unequivocally refined sensors, there is no method published for their calibration according to the method they are used in. So, quality assurance of visual inspection is often neglected. This paper proposes a procedure that may lead to constructive discussion and harmonisation of the interpretation of rating scales among evaluators. It is based on the experience of European countries within the Nordic Wood Preservation Council (NWPC) and CEN/TC38 WG 25 working on the clarification and correct interpretation of rating scales as in EN 252. During three workshops, practical work was performed on wood stakes from the field showing different levels of attack by fungi. In average all evaluators agreed on the evaluation in 21% of the cases, while at least one evaluator disagreed in 67%. In 12% of the cases the stake was given three different ratings. A following discussion led, in almost every case, to agreement on a rating class according to EN 252. We suggest that especially accredited laboratories that perform this type of testing regularly participate in such workshops to "calibrate" themselves with their colleagues and the intention of the standards. A procedure, as described in this paper, for performing quality improvement of the evaluation according to the rating scale could be useful as an informative annex in all standards where visual inspection is used, e.g. EN 252, EN 330 and CEN/TC 12037.
M Klamer, P Larsson Brelid, I Stephan
Report on COST E37 Round Robin Tests – Comparison of results from laboratory and field tests
2013 - IRG/WP 13-20535
A round robin involving 15 European participants was set up in 2006. The round robin consists of both a field test according to the double layer test method and a laboratory test with two different preconditioning methods. When comparing EN 84 preconditioning (two weeks water leaching) with natural preconditioning (1 year in field, above ground) according to CEN/TS 15397, no significant difference could be noted for untreated controls, thermally modified wood or CCA impregnated wood. However, for wood treated with a metal-free organic preservative, a clear difference could be seen where much of the efficacy seen after EN 84 preconditioning is lost when natural preconditioning is used instead. In the field tests, the control pine performs similar in all fields whereas both thermally modified and preservative treated wood performs much better in the Nordic fields than in the Mid- and Southern European fields. The thermally modified wood performs almost as poor as the controls in the Southern European fields, whereas the organic preservative treated wood performs well in these fields. In the six Mid-European fields, the organic preservative treated and thermally modified wood performs equally poor but much better than the controls. The best compliance between field performance and laboratory test results is obtained when comparing the average results from the field tests with results from EN 113 tests with Postia placenta after natural preconditioning according to CEN/TS 15397.
M Westin, E Conti, J Creemers, P-O Flæte, A Gellerich, I Irbe, M Klamer, B Mazela, E Melcher, R Möller, L Nunes, S Palanti, L Reinprecht, E Suttie, H Viitanen
10 year Report on COST E37 Round Robin Tests – Comparison of results from laboratory and field tests
2017 - IRG/WP 17-30718
A round robin involving 15 European participants was set up in 2006. The round robin consisted of both a field test according to the double layer test method and a laboratory test with two different preconditioning methods. The laboratory test results were reported in an earlier IRG paper (IRG/WP13-20535) but are included also in this paper in order to facilitate the comparison with the field test results. As expected, the decay generally developed more rapidly at the southern European compared to the northern European field sites. However, the rank order of the different test groups concerning average decay ratings were the same for most field sites – Untreated pine sapwood controls had the highest decay ratings followed by TMT-UC2 (Thermally Modified Timber treated for use class 2 application), TMT-UC3, metal-free organic preservative in low retention, metal-free organic preservative in high retention, CCA in medium retention, and finally CCA in high retention that had very low decay ratings. The best compliance between field performance and laboratory test results is obtained when comparing the average results from the field tests with results from EN 113 tests with Postia placenta after natural preconditioning according to CEN/TS 15397. When evaluating the test methods it was clear that CEN/TS 15397 before the EN 113 test in laboratory seems to give far more relevant results than EN 113 after preconditioning according to EN 84 (water leaching for 2 weeks). The double layer field test does not function the way it was meant after failure ratings were reached for one or more stakes within a test group leading to collapse of the deck. This has occurred not only at the Southern European field sites but also in some cases for mid-European and Nordic test sites. After this type of collapse has been reached it is doubtful whether there is any point with continuing the test and therefore the test has now been terminated in some fields.
M Westin, E Conti, J Creemers, P-O Flæte, A Gellerich, I Irbe, M Klamer, E Melcher, R Moeller, L Nunes, S Palanti, L Reinprecht, E Suttie, H Viitanen
Proposed methodology for the assessment of safety indexes
1990 - IRG/WP 3562
Safety Indexes (SI)s are developped on the same concept as Efficacy Indexes (EI)s: EIs are retentions of wood preservatives (percentages of the critical values "efficacy") which are presumed efficient for a given biological class of risk. In the same way, SIs are retentions of wood preservatives (percentages of the critical values "safety") which are taken as acceptable for human health and the general environment. EIs and SIs as well are derived from different types of bioassays and related to objectives of quality which may be either regulatory or harmonized within the programmes of the Standard Committees (CEN TC/38 for example). Critical Values are characteristics of wood preservatives; EIs and SIs are characteristics of treated wood; they vary with the different classes of risks.
Report on the activities of the European Standardization Committee CEN/TC 38 'Methods of Testing wood preservatives'
1980 - IRG/WP 279 E
CEN Draft (38 N 460E) Standard: Test method for determining the protective effectiveness of a preservative in the marine environment
1986 - IRG/WP 4132
This European Standard describes a marine test method which provides a basis for asseasing the effectiveness of a wood preservative used to prevent attack of timber in sea-water by marine borers. The method is only suitable for testing preservatives which are intended to prevent attack by marine wood boring organisms of treated timber for use in more or less permanent contact with sea-water. It is not suitable for assessing the effectiveness of preservatives against micro-organisms. The main objective of the method described is to evaluate the relative effectiveness of a wood preservative applied by vacuum/pressure impregnation. For this reason permeable timbers are used throughout so that the protective efficacy of various retentions of the preservative can be determined. However, it is recognized that modifications of the method may be used for other purposes, e.g. to determine the relative efficacy of a preservative treatment or to determine the natural durability of the heartwood and sapwood of a selected timber species. The method is primarily intended for testing in temperate waters where Teredine and Limnoria borers dominate. However, it is also capable of being used in tropics where attack by Pholads and specific Crustacean borers may be very destructive. It has to be considered that the test has to be run for a minimum period (usually for 5 years or until the point of failure) before any interpretation of the results can be made. Variations in the test conditions can be expected from one test site to another depending on temperature, salinity, population density of the various borer species etc. This will inevitably influence the general rate of attack. However, by comparing the results obtained for samples treated with the test product with those obtained with a reference preservative and those obtained with untreated control samples, the relative protective effectiveness of the product tested can be evaluated.
Determination of the preventive efficacy against wood destroying basidiomycetes fungi, EN V 839 - CEN/TC 38 WG 9
1993 - IRG/WP 93-20015
The WG 9 of CEN TC/38 has presented to EC a mycological test to assess efficacy of preservatives applied by surface process. This method is now an experimental standard (EN V 839) which has to be approved by the different european delegations. The following paper is not the standard as it has been proposed but is a presentation of the principle of the method. The experimental standard specifies a laboratory method of test which gives a basis of the assessment of the preventive action of a wood preservative when applied as a surface treatment against Basidiomycetes fungi. This method is applicable to formulations of preservatives in a ready to use form (organic formulations, organic water-dispersible formulations, water-soluble materials). Series of susceptible wood species specimens are treated on longitudinal faces whith the preservative in test using brushing as surface procedure. Test specimens are then exposed by an intermediate mesh to feeder blocks infestedby pure culture of Basidiomycetes fungi in sterile conditions and penetration of fungi is assessed on cross section sawn in the samples at the end of the test.
Report of CEN/TC 38
2002 - IRG/WP 02-20252
Report of CEN/TC 38
2003 - IRG/WP 03-20279
An annual update on activities in CEN/TC 38.
European standardization for wood preservation
1988 - IRG/WP 2321
European standardization for wood preservation
1989 - IRG/WP 2335
Some aspects of laboratory and field testing methods of antitermite wood preservatives
1973 - IRG/WP 235
Various methods for laboratory testing of antitermite activity of wood preservatives are described. The results of simultaneous tests of three water-borne preservatives, according to the various methods are discussed, and comparison is made with results of field tests on the same three preservatives, showing a fairly good accordance between laboratory results and field results.
Rapport sur l'activité du CNE/TC 38 'Méthodes d'essais des produits de préservation du bois'
1980 - IRG/WP 279
Draft Business Plan of CEN/TC 38 - Durability of wood and wood-based products - Introduction
2000 - IRG/WP 00-20207
CEN Technical Committees and Business Planning. The extension of formal business planning to CEN Technical Committees (CEN/TCs) is an important measure which forms part of a major review of business processes (known as 'Optimization'). The aim is to align the CEN work programme with expressed market needs and to ensure the adequate resourcing of projects through their development stages in the CEN/TCs. Your role in the implementation of the Business Planning concept will contribute significantly to the overall effectiveness of European standardization. We express our sincere appreciation and thanks for your time in reviewing this Business Plan.
Blue stain in timber in service. Results of co-operative tests to compare different artificial weathering systems 1981-82
1983 - IRG/WP 2193
The paper describes results of the third phase of co-operative laboratory experiments comparing the effects of different artificial weathering systems on chemicals to control blue-stain in service. Atlas, Xenotest and Marr equipments are shown to give essentially the same results for 5 of the 6 chemicals tested.
A F Bravery, D J Dickinson
Rapport sur l'activité du CEN/TC 38
1983 - IRG/WP 2204
Biocides - Efficacy assessment and doses for wood preservatives (product type 8). Local/geographical aspects. Termite control as case study
1999 - IRG/WP 99-20181
Currently, the efficacy of a wood preservative, as biocidal product type 8, is assessed as a ‚critical value' (CV), an efficient dose (retention in wood at a given depth of penetration). CVs are planned to be adapted for exposure to basic target organisms (5 hazard classes) and additional requirements concerning the occurrence of local target organisms in relation with climate, building design and relevant economical impact. Among them, the termite case study is illustrative. The vote of a french law, on 26 may 1999, aiming to protect consumers and to organize termite control puts termites, a "local target at the euro scale and a universal one in some euro territories", in the spotlights of actuality and helps to point out some of the remaining questions raised by the implementation of Dir 98/8 on Biocides. Based on CEN/TC/38 simulated use tests, which doses have to be used for conditions of exposure and climate, ranging from polar to tropical? Practical proposals are made to take into accound local prescription based on actual target organisms, and move on to standard biocide profiles.
European standardization for wood preservation
1990 - IRG/WP 2359
Committee for Research Co-operation request for OECD sponsorship.
1970 - IRG/WP A 10
Virulence testing of cultures of different origins of the test fungus Coriolus versicolor strain CTB 863 A
1986 - IRG/WP 2267
The virulence of cultures of different origins of Coriolus versicolor CTB 863 A - a strain which is mentioned in EN 113 - was tested. Standard blocks of beech wood were used at temperatures of 20-22°C and 26-28°C and particleboard was tested at 26-28°C. The decay capacity of the different inoculations varied widely, as could be expected it was greatest at the higher temperature level.