The Effect of Low Concentration Fire Retardant Impregnations on Wood Charring Rate and Char Yield

The charring rate and the char yield have been determined for specimens of pine sapwood treated with 15 different inorganic and organic chemicals, many of them known as effective flame retardants, and compared with data for un treated wood. Retentions of 1, 5 and 15% were used. At most, the charring rate was reduced by 17% for impregnated wood (a phosphonate). At 1% retention, no significant effects were obtained. The char yield was increased by 100-150% at 15% retention for some chemicals, but the increase was lower at lower reten tions. The relationship between charring rate and char yield was different for different chemicals.