Identifying Source Odors from Sheetrock

Picture Of Dry walldrywall imported between 2004-2006 from certain areas in China, can release sulfur-like odorous components. These compounds can corrode air conditioning coils and other copper-bearing materials, causing them to be replaced repeatedly. It has been determined that the problem is related to presence of iron disulfide (FeS₂ pyrite). Hydrogen sulfide (H₂S), carbonyl sulfide, sulfur dioxide (SO₂), and carbon disulfide (CS2) are also suspected as culprits. There have been reports that large quantities of drywall produced in China were kept on sea barges for months awaiting permission for importation to the USA. This drywall has a higher than typical density and a higher propensity to off-gas sulfur compounds.

Drywall is usually made of gypsum (hydrated calcium sulfate). Therefore, sulfur is one of the main components present in the sample. All drywall has sulfur in its elemental composition, therefore the odor is not by an analysis of the total sulfur content. There have not been any "exposures" reported from the drywall, so as of today, it seems to be an odor issue and a corrosion of copper-bearing materials issue. All drywall is 99 44/100% Calcium Sulfate hemihydrate. The bad stuff has CS2, COS, dimethyl disulfide, and iron disulfide in it, so far we have not found this with non-odorous drywall. We are doing controls with non-problem drywall. We will know our method detection limit soon.

The extent of the indoor air quality issues related to this is still unclear. EPA is currently investigating the severity of the problem. However, it is well known that exposure to sulfur compounds can create irritation and breathing disorders.

Dade Home Inspections approach for the analysis of drywall samples is diverse. The possible avenues are outlined below:

1. Analysis of the drywall samples for presence by X-ray Fluorescence, X-ray diffraction, or light microscopy. Test 1 is looking for detecting iron disulfide (pyrite).

The limitation to this test is if total Fe in the sample is not >0.5 wt%, we cannot test for pyrite (since XRD cannot detect that low). But we offer comparative analysis of the entire elemental composition between samples and reference samples (drywall samples that are clean, no problems with them).

2. Analysis for presence of Volatile Organic Compounds (VOCs) and H2S using an environmental chamber. Test 2 - is looking for sulfur compounds; carbon disulfide, carbonyl sulfide, hydrogen sulfide, dimethyl disulfide possibly, and we can also look for sulfur dioxide at extra cost.

3. Copper corrosion test can be performed to identify and confirm the presence of substandard drywall (exposure of fresh copper coupons to subsamples of the odorous drywall in presence of humidity). Test 3 - Black sulfide copper corrosion, visual confirmed with electron microscopy.

The limitations to this test - None

4. Sulfur odors may also be produced when anaerobic bacteria utilize certain molecules for growth. Therefore, endotoxin analysis for gram negative bacterial contamination and anaerobic plate count may be recommended. Test 4 - is looking for endotoxin

some bacteria can degrade iron and sulfur compounds to produce sulfurous odors. This may be the actual cause of the problem with drywall. What we test for is:

Endotoxin (Overall bacterial load) $102/sample

Sulfur reducing bacteria $60 /sample Iron related bacteria $60/sample