Concerns about limiting pandemic infectious disease transmission when vaccines are not yet available prompted the Food and Drug Administration (FDA) to develop guidance for marketing respirators for use in public health medical emergencies. This project describes the results of filtering facepiece fit tests using 35 untrained, inexperienced subjects meeting the face size criteria of the National Institute for Occupational Safety and Health bivariate panel, in preparation for an FDA 510(k) application. Quantitative fit factors were measured for each subject on two replicates of each of two N95 filtering facepiece respirators (A and B) using the TSI Portacount Plus with N95 Companion. Subjects received no training or assistance with donning and had no prior experience with wearing respirators. The panel consisted of 20 females and 15 males; 80% were between 18 and 34 years of age. Almost all subjects properly placed the respirator on the face and formed the nose clip. Straps were improperly placed 25% of the time. Users reviewed the donning instructions 73% of the time and performed a seal check 80% of the time. Leaks were observed during 80% of the fit tests, most frequently at the chin during the head up and down exercise. For Respirator A, all but one subject had a 95% fit factor greater than 2 (the minimum required by FDA); one subject had a 95% fit factor of 1.5. All subjects had a 95% fit factor greater than 2.5 for Respirator B. Geometric mean fit factors ranged from 19-28 for these two respirators, and a majority of subjects were able to achieve a fit factor of 10 most of the time. However, fewer than 25% of subjects received the fit factor of 100 expected in workplace settings.