Limited oxygen index levels of impregnated Scots pine wood

• Scots pine samples were treated with 4 wood preservatives with various concentrations.
• Limited oxygen index level was evaluated both for leached and un-leached samples.
• All treatments improved fire retardance of samples despite some chemicals leached out.
• Samples treated with fireproof agent showed the best results.
• LOI of samples treated with boron powder and silicon oil was not changed by leaching.

In this study, effect of various concentrations of boron powder, mixture of boric acid and borax, fireproof agent based on liquid blend of limestone, and silicon oil on limited oxygen index levels (LOI) of S. pine wood was investigated. Wood samples were first vacuum treated with the preservatives, and then were subjected to leaching procedure. Samples treated with fireproof agent showed the best results for improving the fire retardancy of wood, furthermore, samples treated with 25%, 50% and 100% of the solution did not burn. Leaching did not considerably change the LOI of wood samples treated with boron powder and silicon oil; however, LOI levels of samples treated with the mixture of boric acid and borax and fireproof agent were affected by leaching procedure probably arising those preservatives did not chemically bond to main wood components. All treatments improved fire retardancy of samples despite some amount of preservatives leached out from wood.