Effects of retention and distribution of fire retardant chemical on performance of fire retardant treated China fir (Cunninghamia lanceolata) wood

This study investigates the effect of fire-retardant (FR) chemical retention and distributive percentage of FR chemical (DP) on FR performance of FR treated China fir (Cunninghamia lanceolata) wood. The specimens were treated with various concentrations of FR chemical solutions using a vacuum or full-cell process in order to obtain six different DP levels of FR treated woods with DP levels of 34 %, 48 %, 62 %, 76 %, 90 % and 100 %. FR treated woods were tested in accordance with the third grade of surface FR performance as specified by the CNS 6532 standard. Results indicated that the minimum FR chemical retention for meeting the requirement of the third grade standard was 49.2 kg/m(3) and 56.6 kg/m(3) for 100 % and 90 % of DP level specimens, respectively. However, when the specimens exhibited 62 % similar to 34 % of DP level and a FR chemical retention up to 100.5-115.8 kg/m(3) they did not qualify for the third grade standard. The factors of surface FR performance were influenced significantly by the DP level of specimens, the factor of tl (flame lingering time index of material) of FR treated wood could be considered the most sensitive indicator for meeting the requirement of the third grade standard in this study.