Terrorism in the Twenty- First Century: Threats and Responses 

Yonah Alexander

Director, Terrorism Studies Program, George Washington University, 2121 Eye Street, NW Washington, DC 20052, USA

Performance of Air-Purifying Respirators Against Chemical Warfare and Tear Gas Agents 

Z. N. Frund, J.W. Cobes, J. Milius

Mine Safety Appliance Company, P.O. Box 439 Pittsburgh, PA 15230, USA

The Effect of Ambient Concentration and Exercise on PortaCount Quantitative Fit Factors 

Ziqing  Zhuang, C. C. Coffey, W. R. Myers, D. L. McMullin, P. L. Jensen

National Institute for Occupational Safety and Health Mail, Stop H-117, 1095 Willowdale Road, Morgantown, WV 26505-2888, USA

Comparison of the Companion and Modified PortaCount Methods for Fit Testing N95 Respirators 

Ziqing Zhuang, C. C. Coffey, D. L. Campbell, W. R. Myers

Shigematsu, Works Company, Ltd., 267 Yashica Iwatsuki 339- 0046, Japan