4.1 The hygroscopic properties of wood and wood-based products treated with fire-retardant chemicals are often greater than for untreated products. This is particularly true at the higher relative humidity conditions. This higher hygroscopicity sometimes is the cause for staining, decay, poor paint adhesion, and migration and exuding of chemicals and moisture at the high humidities. Corrosion of metal fasteners sometimes also occurs.

4.2 The results obtained with this standard are important in identifying treatments with low hygroscopic properties.

4.3 Results can be useful in determining exposure limitations in service for specific treated products.

4.4 Building codes and other specifications for fire-retardant-treated wood for interior use include requirements based on this test method.

1.1 This test method prescribes the procedure for determining the hygroscopicity of fire retardant treated wood products by determining the moisture content of fire-retardant-treated wood and wood-based product specimens after exposure to a test condition of 92 ± 2 % relative humidity at 81 ± 4°F [27 ± 2°C].

1.2 The text of this test method references notes and footnotes which provide explanatory material. These notes and footnotes (excluding those in tables and figures) shall not be considered as requirements of this test method.

1.3 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.