Citation:

Betancourt, D., T. Dean, A. Evans, AND G. Byfield. Method Analysis of Microbial-Resistant Gypsum Products. Presented at American Society for Microbiology 114th General Meeting, Boston, MA, May 17 - 20, 2014.

Impact/Purpose:

Several commercially available gypsum products are marketed as microbial-resistant. During previous test method efforts in a microbial resistant gypsum wallboard study, a common theme from both stakeholders and product vendors was the need for a unified and accepted method of testing gypsum products that show accurate and repeatable results. The objective of this study was to evaluate currently utilized microbial (fungal) resistant testing methodologies as applied to gypsum products. There are currently a number of methods used for testing for microbial resistance. The results of this study provide useful information to vendors and testing laboratories for decision making of a standard method for testing gypsum products.

Description:

Method Analysis of Microbial-Resistant Gypsum ProductsD.A. Betancourt1, T.R.Dean1, A. Evans2, and G.Byfield2 1. US Environmental Protection Agency, Office of Research and Development, National Risk Management Research Laboratory; RTP, NC 277112. RTI International, RTP, NCSeveral commercially available gypsum products are marketed as microbial-resistant. During previous test method efforts in a microbial resistant gypsum wallboard study, a common theme from both stakeholders and product vendors was the need for a unified and accepted method of testing gypsum products that show accurate and repeatable results. The objective of this study was to evaluate currently utilized microbial (fungal) resistant testing methodologies as applied to gypsum products. There are currently a number of methods used for testing for microbial resistance. The test methods selected for this study were reviewed through a literature search and through the product information of the gypsum board material; all have been used in mold-resistant claims by at least 1 manufacture for at least 1 gypsum panel material. Once the methods were identified, we obtained the documents detailing the specific steps for completing the testing methods as they are currently utilized, including how the method results are to be interpreted. The following methods were compared: (1) ASTM D 6329 (2) ASTM D 3273 (3) ASTM D 2020 (4) ASTM C 1338 (5) ASTM G 21. We tested four types of gypsum wallboard (W) products – W1; W2; W3; W4. All were purchased at retail stores. Of the five methods tested, only the ASTM 6329 gave a quantitative endpoint and has an incubation period of 12 weeks. All of the other methods gave a qualitative endpoint and shorter incubation periods. The major disadvantage of qualitative endpoints is that it is observational and requires interpretation by an individual. One of our major findings was with product W4. All the qualitative methods showed that W4 was mold resistant. However, when using ASTM 6329, it was shown that the naturally occurring mycobiota was present in 6 weeks. The results of this study provide useful information to vendors and testing laboratories for decision making of a standard method for testing gypsum products. Disclaimer: The EPA does not endorse the purchase, sale, or use of any commercial products, services, or testing methods.

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