Fire Retardant Treatments

Two general application methods are available for improving the fire performance of wood with fire retardant chemicals. One method consists of pressure impregnating the wood with water or organic solvent born chemicals. The second method consists of applying fire retardant chemical coatings to the wood surface. The impregnation method is usually more effective and longer lasting. For wood in existing constructions, surface application of fire retardant paints or other finishes offers a practical method to reduce flame spread.

Nochar’s Fire Preventer (NFP) is neither pressure impregnated nor a surface coating. Although applied to the surface, it is absorbed into the cells of the material being treated. It will last the life of the fibers as long as it is protected from running water.

IMPREGNATION

Wood is pressure impregnated with chemical solutions using full-cell pressure processes similar to those used for chemical preservative treatments. Retentions of the chemicals must be fairly high to be effective. Full-cell pressure impregnation provides the most effective method for getting chemicals into the wood at the high retention levels needed for reduced flame spread. Standards C20 and C27 of the American Wood-Preservers’ Association recommend the treating conditions for lumber and plywood. The wood is usually treated in the air-dried or kiln-dried condition, but certain species may be treated green if the wood is first given a steam treatment for periods of up to 4 hours.

The penetration of the chemicals into the wood depends on the species, wood structure, and moisture content since some species are difficult to treat. The degree of impregnation required to obtain a Class A category may not be possible. Certain wood species are incised prior to treatment to improve the depth of penetration. Knife checks and end grain at panel edges improve the ease of impregnation on sheets of plywood, thus eliminating the need for incising. With water-soluble impregnation, only exterior grade wood should be used to prevent the plies from delaminating.

After wood is removed from the treating solution, it must be carefully dried and, in certain cases, cured under the proper conditions. Various laboratories perform fire performance rating tests on these treated materials and maintain lists of products that meet certain standards.

The act of impregnation by the use of positive pressure, combined with the chemicals and final kiln drying, seems to cause degradation of strength of the material being treated. nochar’s Fire Preventer NFP) treatment is either a shell loading chamber process or surface application through spray or dipping. In either case, the chemical loading is not sufficient to cause fiber deterioration nor does it need to be kiln dried. nochar’s Fire Preventer (NFP) is virtually inert and does not activate through heat, which can cause more fiber destruction. nochar’s Fire Preventer has very low hydroscopic properties, therefore, does not tend to leach out due to humidity or moisture. The product will only leach as a result of an abundance of running water.

Coating

Many commercial coating products are available to provide varying degrees of protection to wood against fire. These coatings generally have low surface flammability characteristics and “Intumesce” to form an expanded low density film upon exposure to fire. This film insulates the wood surface below from high temperatures. Also, coatings have ingredients that restrict the flaming of any released combustible vapors. These formulations may contain chemicals that promote the rapid decomposition of the wood surface to charcoal and water rather than forming intermediate volatile flammable products.