1. Mask Design Considerations
2. “Determination of Facepiece Carbon-Dioxide and Oxygen Concentration Levels of Tight Fitting, Powered Air-Purifying Respirators with the Blower Unit Off or Non-Powered Respirators Standard Test Procedure (STP), Procedure No. RCT-APR-STP-0064.” . [Online] Available at http://www.cdc.gov/niosh/npptl/stps/pdfs/RCT-APR-0064.pdf (Accessed May 22, 2006)