In Norway wood has strong traditions as building material in domestic buildings, both for external and indoor use.
Fire Retardant treated wood products have been on the Norwegian market for at least 10 years, and an improvement of both the FR chemicals and the process has improved the products in general. FR treated wood for external use has been especially improved with respect to i.a. hygroscopic properties.
The fact that performance based building regulations were introduced in Norway in 1997 and the improved quality of FR treated wood products have increased the potential use of wood as a building material, especially in multi-storey buildings with more than 2 floors.

The increased opportunity of using FR treated wood requires an increased knowledge about the behaviours of this material with respect to fire.
This study compares Cone Calorimeter test data for untreated spruce (Picea abies) and spruce impregnated with different quantities of fire retardant.
The results show significant differences, not only between the untreated and the FR treated wood, but also between wood with different quantity of fire retardant.
The work shows that it is possible to optimise the content of fire retardant in wood by using the Cone Calorimeter. The parameters included in the comparison are surface charring rate, time to ignition, maximum heat release, average smoke production rate and mass loss. Regression models show that the amount of fire retardant affects some of the fire properties only up to a certain level of FR content.

The results from this study are valid for the test method, heat fluxes, test duration and fire retardant used in this work only. A further investigation to extend the field of validity, will be of great value for manufacturers in the process of optimising the production of Fire Retardant treated wood.

For more information:
Report STF22 A00840 published Aug. 2000 by SINTEF NBL.

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