Fit testing of N95 respirators: A pilot study on respirator design and demographic factors

N95 filtering facepiece respirators (FFRs) approved by the National Institute for Occupational Safety and Health are widely used by healthcare workers to prevent the inhalation of hazardous airborne contaminants. Various nose-clip shapes and respirator styles in N95 FFRs are designed to eliminate gaps between the respirator and the wearer's facial skin, ensuring adequate protection for the wearer. However, variations in facial dimensions across sexes and races may affect the fit and, consequently, the performance of these respirators. The primary objective of this study was to assess the effect of N95 FFR design, specifically the nose-clip shape and respirator style, on the fit factor (FF). The second aim was to assess how subject characteristics, specifically sex and race, affect the respirator fit. Additionally, the efficacy of N95 FFRs may degrade over prolonged use. The authors recently developed a portable device called the Exposure Protection Integrated Communicator (EPIC) that uses dual optical sensors to measure particle concentrations inside and outside the workplace and provide real-time monitoring of the workplace protection factor for FFRs. The EPIC's performance was evaluated by comparing its results with the reference PortaCount fit tester. Two cup-shaped FFRs with different noseclip shapes and six N95 FFRs with various styles were tested. Twenty human subjects were recruited to perform the Occupational Safety and Health Administration approved quantitative fit test (QNFT) protocol by running both PortaCount and EPIC devices in triplicate with each respirator. Results indicated that respirator FF was significantly affected by respirator design and subject facial characteristics. Caucasian males generally achieved the best fit, while Hispanic or Latino females had the poorest fit, highlighting the need for design improvements that account for differences in sex and race. Additionally, the comparison between EPIC and PortaCount demonstrated a strong proportional bias, with EPIC tending to report higher fit factor values, particularly under conditions where the respirator achieved higher fit factors. These findings underscore the need for cautious interpretation and potential calibration before EPIC can be reliably used in occupational settings.