Background:Little is known about health care workers' (HCW) perceptions of, or experiences using, respiratory protective equipment (RPE). We sought to characterize their perceptions and identify reasons underlying inappropriate use. Methods: We conducted 12 focus groups with nurses and nursing assistants at 4 medical centers. We analyzed the thematic content of 73 discrete "stories" told by focus group participants. Results: We identified 5 story types surrounding RPE use: 1) policies are known and seen during work routines; 2) during protocol lapses, use is reinforced through social norms; 3) clinical experiences sometimes supersede protocol adherence; 4) when risk perception is high, we found concern regarding accessing RPE; and 5) HCWs in emergency departments were viewed as not following protocol because risk was ever-present. Discussion: HCWs were aware of the importance of RPE and protocols for using it, and these supported use when protocol lapses occurred. However, protocol adherence was undermined by clinical experience, perceived risk, and the distinct context of the emergency department where patients continually arrive with incomplete or delayed diagnoses. Conclusions: Protocols, visual cues, and social norms contribute to a culture of safety. This culture can be undermined when HCWs experience diagnostic uncertainty or they mistrust the protocol and instead rely on their clinical experiences.Published by Elsevier Inc. on behalf of Association for Professionals in Infection Control and Epidemiology, Inc.