Case Definition

Use of odors as an indicator of drywall associated corrosion is limited.  Odors have not been reported in all homes exhibiting drywall associated corrosion. 

Occupant reported health symptoms have limited use in identifying homes with drywall associated corrosion.  The symptoms reported by occupants are not unique or consistent across affected homes. 

Documenting the presence of odors and/or occupant symptoms may be important to public health agencies, but their relationship to the presence or absence of drywall associated corrosion in homes remains unclear.

Sentinel Indicators of Drywall Associated Corrosion (Possible Case = all 3)

1. The home was constructed or renovated with new drywall since 2001.
2. Observed corrosion of air conditioner evaporator coil exemplified by black corrosion on copper tubing components.  The corrosion can result in refrigerant leakage making it impossible to cool the home requiring coil replacement.  Coil failures indicative of this problem typically occur every 6-14 months
3. Observed metal corrosion, indicated by blackening of one or more of the following:
   
   copper wires, ground wires, and electrical connectors
   un-insulated and un-coated copper pipes and fittings
   chrome-plated bathroom fixtures
   silver and copper jewelry
   mirror backing in bathrooms

If you have answered yes to all three of the above indicators, the home meets the criteria for “possible case”. Continue to Criteria 2 or 3 only if home meets the criteria for “possible case”.  Trained professionals performing home assessments based upon this case definition should use their experience, training, and professional judgment to establish their inspection procedures and sampling strategies. Professional judgment is necessary to determine the number of samples and weight of evidence needed to meet each set of criteria.  A trained professional, not the homeowner, should conduct inspections and testing described in Criteria 2 and 3.

Supporting Indicators of Drywall Associated Corrosion (Probable Case = 1 or more)

1. Observed markings on the back of drywall indicating the country of origin is China.
2. Objective analysis of drywall in home finds Strontium levels exceed 2,000 mg/kg (ppm), indicating the gypsum used in the drywall was probably mined in China.  Analytical methods commonly used for this include XRF and ICP. (2, 3, 5, & 7-12)

If you have met the criteria for “possible case” and answered yes to at least one of the above indicators in Criteria 2, the home meets the criteria for “probable case”.  These criteria do not confirm that the drywall causes corrosion. Identifying the origin of the drywall is considered a screening tool for suspect drywall, but confirmation requires analysis described in Criteria 3.

Confirmatory Evidence of Drywall Associated Corrosion (Confirmed Case = 1 or more)

1. Elemental sulfur (Orthorhombic sulfur, cyclooctasulfur, S8) content of gypsum core exceeding 10 mg/kg (ppm), indicating the gypsum in drywall samples from the home contains the source material that is believed to contribute to the reduced sulfur gasses emitted from corrosive drywall. Analytical methods commonly used for this include GC/ECD, GC/MS, or HPLC. (1-4, 6, & 8-11)
2. Laboratory analysis of suspect drywall headspace for reduced sulfur gas emissions (H2S, COS, CS2) indicating drywall samples from the home emit reduced sulfur gasses capable of causing copper corrosion. Analytical methods commonly used for this include GC/SCD.6 Results that are indicative of corrosive drywall must be established by each laboratory based upon internal procedures, comparison to control samples, and validated methods.Qualitative analysis of suspect drywall for its ability to cause corrosion/blackening of copper under controlled conditions, indicating drywall samples from the home emit gasses capable of corroding copper.  Results that are indicative of corrosive drywall must be established by each laboratory based upon internal procedures, comparison to control samples, and validated methods.

If you have met the criteria for “possible case”, ruled out other sources of hydrogen sulfide as significant contributors to copper corrosion in the home, and receive positive results on a sufficient number of samples from one or more of the above evaluations in Criteria 3, the home meets the criteria for a “confirmed case”. Some confounding factors that should be excluded as causes of observed corrosion are hydrogen sulfide from well water, sewer gas, or soil gas.