The CDPH established a stockpile of respirators for use by healthcare personnel during an outbreak of pandemic influenza. The stockpile included an assortment of FFRs including approximately 32 million 3M Model 8000 N95. The CDPH's stockpile of respirators was made available for healthcare worker use during an outbreak of pandemic influenza in Fall, 2009. In addition to the CDPH's reserves, the CDC distributed a supplement of approximately 4 million 3M Model 8000 N95 FFRs to the CDPH from the federal government's Strategic National Stockpile, which is maintained and managed by CDC. Healthcare facilities within California that were experiencing shortages of respirators for the protection of healthcare personnel received respirators distributed from the CDPH stockpiled respirators, including this 3M model. On December 23, 2009, NIOSH received a request for assistance from Cal/OSHA. Cal/OSHA was concerned that a large healthcare organization was unable to successfully fit test their healthcare workers with the 3M Model 8000 N95 FFR received from the California stockpile. The healthcare organization conducted the initial set of fit tests using the Bitrex qualitative fit test protocol, and none of the approximately 20 workers who were fit tested obtained an acceptable fit (pass rate of 0%). A second group of 20 workers were reported to have obtained a fit test pass rate of 40% (8 of 20) with fit tests conducted by 3M representatives using the TSI PortaCount with N95 Companion quantitative fit test protocol. The California experience with these devices raised questions about whether the subject units had a defect of some type whereby they may have been non-conforming to the NIOSH approval. SMEs from the NIOSH NPPTL conducted the technical assistance investigation. The purpose of the NIOSH investigation was to determine whether the fit test pass rate reported at the various facilities of a California healthcare organization resulted from any defect in the units' characteristics on which the product was certified (e.g., filter efficiency at the N95 criteria, workmanship, or quality of manufacture) as believed by Cal/OSHA and CDPH. To address the concerns, NIOSH requested and received samples from the remaining stockpiled 3M Model 8000 respirators from CDPH for inspection, testing and evaluation. The activities were divided into five parts: (1) assessment of compliance with requirements for NIOSH respirator certification, (2) assessment of conformance with quality assurance provisions incorporated into the NIOSH approval, (3) respirator research review, and (4) fit test trials using the CDPH-supplied 3M 8000 respirators. This investigation was limited to conformity assessment of the respirators to the NIOSH approval requirements and did not include efforts to evaluate the California healthcare organization's fit testing programs, or to conduct additional fit testing on the actual healthcare workers who failed the California fit tests. The investigation revealed that the 3M Model 8000 respirators complied with all applicable approval requirements, which do not include assessment of fit characteristics. The respirators were additionally tested for their ability to fit test subjects representative of the NIOSH Bivariate fit test panel. The sample respirators demonstrated fit test passing results on 22 and 25 of the 40 subjects in the two sets of trials. The investigation found no issues or concerns of non-compliance with normal quality control practices or the requirements of the 3M quality control plan during the manufacturing of the respirators in the CDPH stockpile. As a result of these findings, no further actions will be taken.