at Baltimore (UMAB), for his interest in and willingness to guide and support her research efforts. She would also like to thank David Harrah, Human Research and Engineering Directorate (HRED) of the U.S. Army Research Laboratory (ARL), for his expert guidance in the use and study of protective masks, as well as for an extensive review of her manuscript. The author would like to thank many others who provided assistance along the way: Ronald Carty, ARL, for his skilled preparation of photos and illustrations; Vince Novak, of UMAB, for his guidance in evaluating behavior of head harness straps; Chris Karwacki, of the Edgewood Research, Development, and Engineering Center (ERDECI), in the use of the breathing simulator; Corey Grove, David Caretti, William Fritch, all of ERDEC, and Anand Kasbekar, Ph.D., of Visual Sciences, Inc., for reviewing protocols and supporting this project; the Simulation Systems Branch, HRED, ARL, for constructing test fixtures and repairing equipment; and the ERDEC mask prototyping shop for supplying the equipment and materials necessary for this effort.