Effect of Environmental Factors on Sulfur Gas Emissions from Problem Drywall
Problem drywall installed in U.S. homes is suspected of being a source of odorous and potentially corrosive indoor pollutants. The U.S. Consumer Product Safety Commission’s (CPSC) investigation of Chinese drywall incorporates three parallel tracks:
- evaluating the relationship between the drywall and reported health symptoms;
- evaluating the relationship between the drywall and electrical and fire safety issues in affected homes; and
- tracing the origin and the distribution of the drywall. To assess the potential impact on human health and to support testing for electrical and fire safety, the CPSC has initiated a series of laboratory tests that provide elemental characterization of drywall, characterization of chemical emissions, and in-home air sampling.
The chemical emission testing was conducted at Lawrence Berkeley National Laboratory (LBNL). The LBNL study consisted of two phases. In Phase 1 of this study, LBNL tested thirty drywall samples provided by CPSC and reported standard emission factors for volatile organic compounds (VOCs), aldehydes, reactive sulfur gases (RSGs) and volatile sulfur compounds (VSCs). The standard emission factors were determined using small (10.75 liter) dynamic test chambers housed in a constant temperature environmental chamber. The tests were all run at 25°C, 50% relative humidity (RH) and with an area-specific ventilation rate of ~1.5 cubic meters per square meter of emitting surface per hour [m3/m2/h]. The thirty samples that were tested in Phase 1 included seventeen that were manufactured in China in 2005, 2006 and 2009, and thirteen that were manufactured in North America in 2009.
The measured emission factors for VOCs and aldehydes were generally low and did not differ significantly between the Chinese and North American drywall. Eight of the samples tested had elevated emissions of volatile sulfur-containing compounds with total RSG emission factors between 32 and 258 micrograms per square meter per hour [μg/m2/h]. The dominant sulfur containing compounds in the RSG emission stream were hydrogen sulfide with emission factors between 17 – 201 μg/m2/h, and sulfur dioxide with emission factors between 8 – 64 μg/m2/h. The four highest emitting samples also had a unique signature of VSC emissions including > 40 higher molecular weight sulfur- containing compounds although the emission rate for the VSCs was several orders of magnitude lower than that of the RSGs. All of the high emitting drywall samples were manufactured in China in 2005-2006.
Results from Phase 1 provided baseline emission factors for drywall samples manufactured in China and in North America but the results exclude variations in environmental conditions that may exist in homes or other built structures, including various combinations of temperature, RH, ventilation rate and the influence of coatings such as texture and paints.
The objective of Phase 2 was to quantify the effect of temperature and RH on the RSG emission factors for uncoated drywall, and to measure the effect of plaster and paint coatings on RSG emission factors from drywall. Additional experiments were also performed to assess the influence of ventilation rate on measured emission factors for drywall.