Underwriters’ Laboratories Conduct Tests on Various Types of Woods With and Without Treatment—Results Satisfactory

FIREPROOFED lumber, a dream for centuries, apparently is at last a reality.

This recent contribution of science which practically robs wood of its ability to burn and renders it instead an obstacle in the path of fire, is made known after a comprehensive examination just completed by the Underwriters’ Laboratories.

“Practically noncombustible and nonflammable” is the evaluation of the effectiveness of the fireproofed wood tested. Walls or floors of this material, tests show, will act as fire-stops and prevent the passage of fire through them, thus confining the conflagration to its point of origin and preventing its spread. It is further stated in the report approving this material that its fireresisting properties will last throughout its useful life. These and the other conclusions drawn are the results of a great variety and number of tests.

The material investigated and approved is fireproofed lumber of red oak and maple for flooring and interior trim. The successful fireproofing of this lumber is effected by a method not unlike that used in the treatment of telegraph poles, railroad ties, fence posts, etc., with creosote for protection against decay, except that incombustible salts are used in the case of the fireproofed lumber. The technique of the process is exacting, as its success depends largely upon getting just the correct amount of salts into the wood as a greater or lesser amount fails to give the desired results.

In the tests conducted at Underwriters’ Laboratories actual fire conditions were created. Whole floors of the fireproofed lumber, and others of untreated lumber, were subjected to intense heat in gas-fired furnaces especially designed for such work. Through windows the behavior under fire of the fireproofed and the untreated floors was observed and compared by one group of engineers, while a hundred feet away other engineers recorded the temperatures of the floors by means of meters connected with thermocouples.

The fireproofed floors came from the furnace at the completion of the tests blackened and charred on the exposed surface but intact and otherwise sound, having successfully stood as a barrier against the fire and prevented its passage. The untreated floors did not fare so well. They ignited and, on completion of the tests, were burning on both the exposed and unexposed surfaces, the fire having eaten througn them.

Tests Show Merit of Treatment

Fire spread tests in a horizontal furnace, where the flames were played on one end of the flooring, were also conducted. Chemical and calorimetric tests were performed on numerous samples conditioned in various ways. Test floors were repeatedly washed to determine the lasting quality of the fireproofing. For thirty days an automatic machine scrubbed them with cleaning compound, flushed with clear water and dried the surface every thirty minutes and then repeated the operations. All of these tests, as well as the Dunlap fire tube, timber and crib tests conducted on a great number of samples, showed the merits of the fireproofed lumber.

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