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CPSC Interim Guidance to ID Corrosive Drywall


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Interim Guidance – Identification of Homes with Corrosion from Problem Drywall1

by the Consumer Product Safety Commission

and the Department of Housing and Urban Development

January 28, 2010

Executive Summary

This preliminary identification guidance represents what the Federal Interagency Task Force on Problem Drywall believes is the best approach based on the limited information available today. This identification guidance is based primarily on the presence of metal corrosion in homes as well as other indicators of problem drywall. Additional work will continue to validate these methods and the identification guidance will be modified as necessary.

Identification Method

The identification process is two steps: (1) an initial or threshold inspection to find visual signs of metal corrosion and evidence of drywall installation during the relevant time period, and (2) the identification of corroborating evidence or characteristics.

Step 1: Threshold Inspection

Visual inspection2 must show:

  • (a) Blackening of copper electrical wiring and/or air conditioning evaporator coils; and

(b) The installation of new drywall (for new construction or renovations) between 2001 and 2008.

A positive result for this step (including both criteria) is a prerequisite to any further consideration.

Step 2: Corroborating Evidence

Because it is possible that corrosion of metal in homes can occur for other reasons, it is important to obtain additional corroborating evidence of problem drywall. Homes with the characteristic metal corrosion problems must also have at least 2 of these corroborating conditions if the new drywall was installed between 2005 and 2008. For installations between 2001 and 2004, at least 4 of the following conditions must be met. Collecting evidence of these corroborating conditions will in some cases require professional assessors and/or testing by analytical laboratories.

  • (a) Corrosive conditions in the home, demonstrated by the formation of copper sulfide on copper coupons (test strips of metal) placed in the home for a period of 2 weeks to 30 days or confirmation of the presence of sulfur in the blackening of the grounding wires and/or air conditioning coils;

(b) Confirmed markings of Chinese3 origin for drywall in the home;

© Strontium levels in samples of drywall core found in the home (i.e. excluding the exterior paper surfaces) exceeding 1200 parts per million (ppm);

(d) Elemental sulfur levels in samples of drywall core found in the home exceeding 10 ppm;

(e) Elevated levels of hydrogen sulfide, carbonyl sulfide and/or carbon disulfide emitted from samples of drywall from the home when placed in test chambers using ASTM Standard Test Method D5504-08 or similar chamber or headspace testing4;

(f) Corrosion of copper metal to form copper sulfide when copper is placed in test chambers with drywall samples taken from the home.

Detailed Description

Introduction

This preliminary identification guidance represents what the Federal Interagency Task Force on Problem Drywall believes is the best approach based on the limited information available today. We recognize that important additional guidance is still needed to clarify qualifications for inspectors and test laboratories and to describe methods for making the measurements in the criteria defined herein. This interim identification guidance is being released in recognition of the immediate need of homeowners for this information. Consumers should exercise caution in contracting for testing, and should be diligent in confirming the references, qualifications, and background of individuals and firms that offer such testing5. Scientific investigations have moved as quickly as possible to understand the complex problems presented by the issue of Chinese6 drywall. The scientific work completed to date by the Federal Interagency Task Force has been essential to building the foundation for decision-making by homeowners and local, state and federal authorities.7 The investigation continues on several fronts to expand our understanding of this issue – but the Task Force believes that current information is sufficient to develop interim guidance on how to identify homes with problems associated with this drywall.

Findings have shown a strong association between the presence of problem drywall and metal corrosion in homes. The results of investigations reported by the Federal Interagency Task Force provide criteria and indicators for identifying those homes. The Task Force developed this preliminary guidance document based on these findings.

This identification guidance is based primarily on the presence of metal corrosion in homes as well as other indicators of problem drywall. It is possible to misclassify homes because of other possible sources of metal corrosion such as volatile sulfur compounds from sewer gas, well water, and outdoor contaminants that may enter the home independent of the drywall in the home. Homes may also be misclassified as having no drywall problem due to the absence of characteristics found to be typical in the limited testing to date. Given these limitations, additional work will continue to validate these methods and the identification guidance will be modified as necessary.

Identification Method

The identification process will be two steps: (1) an initial or threshold inspection to find visual signs of metal corrosion and evidence of drywall installation in the relevant time period, and (2) the identification of corroborating evidence or characteristics.

Step 1: Threshold Inspection

A visual inspection shall seek to identify blackening of copper electrical wiring and/or air conditioning evaporator coils (or documentation of replacement of evaporator coils due to blackened corrosion causing failure), and the installation of new drywall (for new construction or renovations) between 2001 and 2008. Meeting both criteria for this step is a prerequisite for further consideration.

Rationale

Visual observations of corrosion of air conditioning evaporator coils and/or electrical wiring by trained inspectors is believed to be a prerequisite for consideration of a home as having problem drywall. The Florida Department of Health has long included such corrosion as part of its definition of problem drywall homes8,9. It is appropriate to limit the dates to the relevant time period, as this corresponds to the vast majority of complaints received by the Consumer Product Safety Commission (CPSC), also much older homes could exhibit corrosion due to different sources acting over longer periods of time.

A CPSC contractor completed a detailed study of 51 homes in Florida, Louisiana, Virginia, Alabama, and Mississippi; the report was issued on November 23, 2009 and is available on www.drywallresponse.gov. This investigation included inspections of each home for the presence and extent of corrosion. Copper and silver metal test strips, called “coupons,â€

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