Hall also investigated the role of spices in food preservation. It was common knowledge that certain seasonings had antimicrobial properties, but Hall and co-worker Carroll L. Griffith found that some spices carried many bacteria, as well as yeast and mold spores. To counter these problems, they patented in 1938 a means to sterilize spices through exposure to ethylene oxide gas, a fumigant. This method was all but abandoned upon the discovery that ethylene oxide was a toxic carcinogen. Hall and Griffith later promoted the use of ethylene oxide for the sterilization of medical equipment, helping to advance an idea that had been around for several years.