Citation:

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

Impact/Purpose:

The objective of this study was to evaluate microbial (fungal) resistant testing methodologies as applied to gypsum products. There are currently a number of methods used to test 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 manufacturer and for at least 1 gypsum panel material. The results of this study provide useful information to vendors and testing laboratories as they make decisions regarding a standard method for testing gypsum products.

Description:

Abstract: Several commercially available gypsum products are marketed as microbial-resistant. During previous test method research on 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 microbial (fungal) resistant testing methodologies as applied to gypsum products. There are currently a number of methods used to test 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 manufacturer and 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) EPA ETV/ESTE (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 EPA ETV/ESTE 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 EPA ETV/ESTE protocol, it was shown that the naturally occurring mycobiota showed growth within an incubation period of 6 weeks. The results of this study provide useful information to vendors and testing laboratories as they make decisions regarding a standard method for testing gypsum products.

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