An Evaluation of Borates and Other Inorganic Salts as Fire Retardants for Wood Products

Six chemical materials–FR 28R; (NH4) 2HPO4; (NH4) AWPA Type C; AWPA Type D; and Proprietary (composition unknown)–were tested for their effectiveness as fire retardants for Douglas-fir, southern pine, and western hemlock lumber and exterior grade Douglas-fir plywood. Flame-spread tests indicate that borates are effective fire retardants for the wood tested in both the 10-minute and 30-minute ASTM E-84 tests. In these tests, fuel contribution was zero in most cases; smoke was zero, in all but one test. Additional tests will be necessary to develop a definite correlation between the ASTM E-84 tunnel test and the ASTM E-162 radiant panel test. Corrosion of metals and metal fasteners was less pronounced when in contact with wood treated with borate salts than with other treating compositions. Strength properties of wood generally are not appreciably affected by fire-retardant-salt treatments. Borate treatment at the 7 and 10 percent level in particleboard has proved to be an effective means of rendering this type of product fire retardant.

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