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Subject Odorous Drywall - Chinese Drywall Syndrome

Odorous drywall- AKA Chinese Drywall Syndrome

 

Chinese Drywall”, also called odorous gypsum wallboard, is an emerging issue in the IAQ community. The material, which has been identified in new and remodeled homes in Florida, Louisiana, Texas, and reported elsewhere, has been determined to emit chemicals that cause characteristic sulfide odors, black discoloration of metal fixtures, electrical components, and domestic water piping, as well as black sulfide corrosion of HVAC components leading to failure. There are also reports of health effects associated with the material. The selection of the most appropriate analysis approach to determine the source or the sources of the sulfur-based odor in the sub-par drywall is still controversial. EMSL Analytical offers a panel of tests that covers a range of issues associated with the odorous drywall problems. The elemental analysis of the bulk drywall is performed to determine the concentration of impurities (such as iron, strontium, magnesium, phosphorus, chlorine) in a direct comparison with samples of domestically-produced drywall tested negative for all the problems associated with the “Chinese drywall” syndromes. The exact identity of the compounds formed by these elements is still under investigation; however, SEM/EDX analysis of selected impurities extracted from the odorous drywall revealed the presence of sulfur in association with Fe and Sr, indicating the presence of possible pyrite (FeS2) and strontium sulfide (SrS). These compounds could decompose in hot and humid conditions. SrS, for example, slowly releases H2S in moist air. It is speculated that the presence of these compounds in low concentrations as impurities is related to mined gypsum. X-ray Diffraction (XRD) is used to determine the crystalline components in the samples. Off-Gas Sampling by GC/MS is a method that directly addresses the odor associated with the problem. Samples of the gases collected from wallboard samples in the laboratory via environmental chamber approach consistently showed elevated levels of carbon disulfide and carbonyl sulfide. Corrosion propensity of the odorous drywall is performed in simulated corrosion experiments performed in our laboratory using drywall that was tested positive for sulfur-containing gases. The simulated corrosion testing showed variable time-frames for developing the black copper corrosion process. In accelerated conditions, the advanced corrosion in the form of black films of copper sulfide developed on the surface of copper coupons in as fast as 13 days of exposure at 95% humidity and 98oF. In gentler exposure conditions, the corrosion was less advanced and it developed in 6-8 weeks of exposure. The microbiological analysis covers the approach where the sulfur odors may be produced when certain aerobic and anaerobic bacteria utilize certain molecules for growth. Therefore, endotoxin analysis for gram negative bacterial contamination and sulfur reducing and iron related bacterial tests are recommended.

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